User identity privacy protection against fake base stations

Abstract

Disclosed is a technique for protecting a user identity by encrypting a user permanent identifier (SUPI) using a set of one-time temporary asymmetric keys generated by a user equipment (UE) and a key provided by the network to form a one-time user hidden identifier (SUCI). Encrypting the SUPI to form the SUCI can mitigate snooping by malicious network entities such as fake base stations. The UE is restricted from providing unencrypted SUPI through an unauthenticated connection with a network entity. In some cases, the UE uses a trusted symmetric fallback encryption key K FB or trusted asymmetric fallback public key PK FB to authenticate messages from an unauthenticated network entity and / or to encrypt the SUPI to form a fallback SUCI for communicating messages with the unauthenticated network entity FB .

Description

Technical Field

[0001] The described embodiments describe techniques for protecting a user identity from a fake base station when transmitting messages between a wireless device and a wireless network entity, the messages including a limited-use fallback encryption key and a single-use encrypted user identity. Background Art

[0002] Many wireless devices are configured to use a removable universal integrated circuit card (UICC) that enables the wireless device to access services provided by a mobile network operator (MNO). Specifically, each UICC includes at least a microprocessor and a read-only memory (ROM), wherein the ROM is configured to store an MNO profile that the wireless device can use to register and interact with the MNO to obtain wireless services through a cellular wireless network. Typically, the UICC takes the form of a small removable card (commonly referred to as a subscriber identity module (SIM) card) that is configured to be inserted into a UICC receiving area included in the wireless device. In recent implementations, the UICC is embedded directly into the system board of the wireless device. These embedded UICCs (eUICCs) can provide several advantages over traditional removable UICCs. For example, some eUICCs include a rewritable memory that can facilitate the installation, modification and / or deletion of one or more electronic SIMs (eSIMs) that can provide new and / or different services and / or updates for accessing extended features provided by the MNO. The eUICC may store multiple MNO profiles (also referred to herein as eSIMs) and may eliminate the need to include a UICC reception area in the wireless device.

[0003] The MNO profile includes a globally unique subscriber permanent identifier (SUPI), such as an International Mobile Subscriber Identity (IMSI), by which a user subscribing to services provided by the MNO can be uniquely identified through a cellular wireless network. The SUPI includes a Mobile Country Code (MCC), a Mobile Network Code (MNC), and a Mobile Subscriber Identification Number (MSIN). Certain messages sent between a cellular wireless network and a wireless device may include the SUPI in a clearly readable, unencrypted format, and thus the SUPI is open to snooping through passive monitoring or active request and reply capture techniques. Summary of the invention

[0004] Representative embodiments describe techniques for protecting user identity by encrypting a user permanent identifier (SUPI) using a one-time temporary asymmetric key generated by a user equipment (UE) and a key provided by the network to form a user hidden identifier (SUCI). Encrypting the SUPI to form the SUCI can mitigate snooping and can be based on a temporary asymmetric key pair generated by the UE and an additional key (including a combination of symmetric keys and / or asymmetric keys) generated by a wireless network entity. The keys can be used once and / or updated over time. To prevent attacks from malicious network entities (e.g., fake base stations), the UE is restricted from providing unencrypted SUPI through an unauthenticated connection with the network entity. In some cases, the UE uses a symmetric fallback encryption key K FB or asymmetric fallback public key PK FB to authenticate messages from unauthenticated network entities and / or to encrypt SUPI to communicate with unauthenticated network entities.

[0005] The UE encrypts a mobile user identifier, such as the MSIN portion of a SUPI, using a one-time encryption key to generate a one-time use SUCI. To authenticate with the cellular wireless network, the UE sends uplink (UL) messages to the cellular wireless network entity, which include a one-time SUCI, a corresponding one-time temporary UE public key, and an identifier of the network public key used to encrypt the SUCI. The cellular wireless network entity may verify the network public key and decrypt the SUCI by deriving an encryption key using the one-time temporary UE public key and a network secret key corresponding to the verified network public key. A malicious network entity will not be able to decrypt the SUCI without the network secret key and may attempt to obtain the SUPI by requesting the SUPI directly from the UE and / or by impersonating a real cellular wireless network entity by sending a fake network public key to the UE for encrypting the SUPI. The UE distinguishes the malicious network entity from the real cellular wireless network entity by verifying a signature included in a downlink (DL) message from the real cellular wireless network entity providing the new network public key. The signature is based on a trusted fallback encryption key, such as K, that the fake base station will not be able to access. FB or SK FB In some embodiments, when the SUCI encrypted with the network public key fails to authenticate, the UE provides the SUCI encrypted with the fallback encryption key to the cellular wireless network entity. In some embodiments, when the SUCI encrypted with the fallback encryption key fails to authenticate, the UE stops the attach procedure and provides a denial of service indication.

[0006] To uniquely authenticate to the cellular wireless network, the UE sends UL messages that include different one-time SUCIs, corresponding one-time temporary UE public keys, and a network public key identifier. When the network public key is updated, for example, by an over-the-air (OTA) update of a secure connection between the UE and a cellular wireless network server and / or by a downlink (DL) message sent to the UE by a network entity (e.g., by the cellular wireless network entity or by a third-party server providing operator binding updates), previously generated unused one-time SUCIs are discarded and additional new one-time SUCIs are generated based on newly derived encryption keys that are based on the updated network public key and additional one-time temporary UE secret keys.

[0007] In some embodiments, it is not necessary to use a fallback encryption key to verify the updated network public key provided via a secure connection from a trusted network entity. In some embodiments, the fallback encryption key is updated by the trusted network entity via a secure connection with the UE (e.g., via an operator binding update). The fallback encryption key may be rarely updated, or not updated at all in some embodiments. In some embodiments, the fallback encryption key is a symmetric key stored in a tamper-proof hardware security element (SE) of the UE. In some embodiments, the fallback encryption key provides a higher level of security strength (e.g., 256-bit encryption) compared to the normal encryption of the SUPI (e.g., 128-bit encryption). In some embodiments, the fallback encryption key is limited to the threshold number of times the UE can use the fallback encryption key. In some embodiments, the fallback encryption key expires after a period of time. In some embodiments, the UE encrypts the SUPI based on the combination of the updated network public key and the fallback encryption key to form a fallback SUCI, wherein when the normally encrypted SUCI fails, the fallback SUCI is used for authentication. Both the normally encrypted SUCI and the fallback SUCI can be limited to a one-time message for sending to a network entity. Using a unique one-time SUCI, the UE maintains privacy from pseudo base stations that attempt to track the UE based on observing reuse of encrypted identifier values.

[0008] The present invention is provided for the purpose of summarizing some exemplary embodiments only, so as to provide a basic understanding of some aspects of the subject matter described herein. Therefore, it should be understood that the above-mentioned features are only examples and should not be interpreted as narrowing the scope or essence of the subject matter described in the present invention in any way. Other features, aspects and advantages of the subject matter described herein will become apparent through the following detailed description, drawings and claims.

[0009] Other aspects and advantages of the embodiments described herein will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate by way of example the principles of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The included drawings are for illustrative purposes and are only used to provide examples of possible structures and arrangements of the disclosed apparatus and methods for providing wireless computing devices. These drawings in no way limit any changes in form and detail that may be made to the embodiments by those skilled in the art without departing from the spirit and scope of the embodiments. The embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings, in which like reference numerals refer to like structural elements.

[0011] Figure 1 A block diagram showing different components of an example system configured to implement the various techniques described herein, according to some embodiments.

[0012] Figure 2 According to some embodiments, Figure 1 A block diagram of a more detailed view of exemplary components of a system.

[0013] Figure 3 A block diagram of an exemplary system for capturing a user identity according to some embodiments is shown.

[0014] Figure 4A and Figure 4B A flow chart showing a prior art encryption technique for protecting a user's identity.

[0015] Figure 5A An example message exchange is shown that uses pre-encrypted user identities to protect the privacy of the user identities in accordance with some embodiments.

[0016] Figure 5B An example message exchange is shown for protecting the privacy of a user identity, including updating an encrypted user identity, according to some embodiments.

[0017] Figure 5C Another example message exchange for protecting the privacy of a user identity, including updating an encrypted user identity, is illustrated in accordance with some embodiments.

[0018] Figure 5D Another example message exchange for protecting the privacy of a user identity, including updating an encrypted user identity after verifying an updated network public key, is illustrated in accordance with some embodiments.

[0019] Figure 5EYet another example message exchange for protecting the privacy of a user identity, including updating an encrypted user identity after verifying an updated network public key, is illustrated in accordance with some embodiments.

[0020] Fig. 6A and Figure 6B An example message exchange is shown for protecting the privacy of a user's identity, including using fallback encryption keys to protect communications during authentication error conditions, in accordance with some embodiments.

[0021] Fig. 7A , Figure 7B , Figure 7C , Fig.7D , Fig. 7E , Figure 7F , Figure 7G and Figure 7H A flow diagram of an exemplary modified encryption technique for protecting user identity according to some embodiments is shown.

[0022] Fig.7I Another example message exchange is shown for protecting the privacy of a user's identity, including using fallback encryption keys to protect communications during authentication error conditions, in accordance with some embodiments.

[0023] Figure 8 A flow diagram is shown of an exemplary sequence of actions for protecting the privacy of a user's identity during a network attachment process according to some embodiments.

[0024] Fig. 9 A block diagram illustrating an example of overlapping time periods using network keys according to some embodiments.

[0025] Fig. 10A , Fig. 10B and Fig. 10C An exemplary flow chart of actions performed by a UE to implement a method for protecting the privacy of a user identity according to some embodiments is shown.

[0026] Fig.11 Shown is a detailed view of a representative computing device that can be used to implement the various methods described herein, according to some embodiments. DETAILED DESCRIPTION

[0027] Representative applications of the apparatus and methods according to the embodiments described in the present invention are provided in this section. These examples are provided only to add context and to help understand the described embodiments. It will therefore be apparent to those skilled in the art that the embodiments currently described may be practiced without some or all of these specific details. In other instances, well-known process steps are not described in detail to avoid unnecessarily obscuring the embodiments currently described. Other applications are possible, so that the following examples should not be considered restrictive.

[0028] According to various embodiments described herein, the terms "wireless communication device", "wireless device", "mobile device", "mobile station", and "user equipment (UE)" may be used interchangeably herein to describe one or more common consumer electronic devices that may be capable of performing the processes associated with various embodiments of the present disclosure. According to various specific implementations, any of these consumer electronic devices may relate to: a cellular phone or smart phone, a tablet computer, a laptop computer, a notebook computer, a personal computer, a netbook computer, a media player device, an e-book device, Devices, wearable computing devices, and any other type of electronic computing device with wireless communication capabilities, which wireless communication capabilities may include communication via one or more wireless communication protocols, which wireless communication protocols, such as protocols used to communicate on the following networks: wireless wide area networks (WWAN), wireless metropolitan area networks (WMAN), wireless local area networks (WLAN), wireless personal area networks (WPAN), near field communication (NFC), cellular wireless networks, fourth generation (4G) long term evolution (LTE), advanced LTE (LTE-A), and / or fifth generation (5G) or other currently or future developed advanced cellular wireless networks.

[0029] In some embodiments, the wireless communication device may also operate as part of a wireless communication system, which may include a group of client devices, which may also be referred to as stations, client wireless devices, or client wireless communication devices, which are interconnected to an access point (AP), for example, as part of a WLAN, and / or interconnected with each other, for example, as part of a WPAN and / or "ad hoc" wireless network. In some embodiments, the client device may be any wireless communication device capable of communicating via WLAN technology (e.g., according to a wireless local area network communication protocol). In some embodiments, the WLAN technology may include a Wi-Fi (or more generally, a WLAN) wireless communication subsystem or radio component, which may implement the Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology, such as one or more of the following: IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE 802.11n; IEEE 802.11-2012; IEEE 802.11ac; or other currently or future developed IEEE 802.11 technology.

[0030] In addition, it should be understood that some UEs described herein may be configured as multimode wireless communication devices that are also capable of communicating via different third generation (3G) and / or second generation (2G) RATs. In these cases, the multimode user equipment (UE) may be configured to prefer attaching to an LTE network that provides a faster data rate throughput over other 3G legacy networks that provide a lower data rate throughput. For example, in some embodiments, the multimode UE may be configured to fall back to a 3G legacy network, such as an evolved high speed packet access (HSPA+) network, or a code division multiple access (CDMA) 2000 evolution-data only (EV-DO) network when LTE and LTE-A networks are otherwise unavailable.

[0031] The representative embodiments described herein describe a technique for protecting the user identity in messages transmitted via an unauthenticated connection between a wireless device (e.g., UE) and a wireless network entity by encrypting a user permanent identifier (SUPI) using a one-time temporary asymmetric key generated by a user equipment (UE) and a key provided by the network to form a user hidden identifier (SUCI). Encrypting SUPI to form SUCI can mitigate snooping and can be based on a temporary asymmetric key pair generated by the UE and an additional key (including a combination of symmetric keys and / or asymmetric keys) generated by the wireless network entity. The asymmetric key pair can be used once and / or updated over time. In order to prevent attacks from malicious network entities (e.g., fake base stations), the UE is restricted from providing unencrypted SUPI through an unauthenticated connection with a network entity. In some cases, when authentication fails, the UE uses a trusted fallback encryption key to verify messages from an unauthenticated network entity and / or encrypt SUPI to communicate with the unauthenticated network entity. In some embodiments, the UE maintains a trusted fallback encryption key in a tamper-proof hardware security element (SE) (e.g., in a UICC, eUICC, SIM card) or a secure isolation processor (SEP).

[0032] A malicious network entity, such as a pseudo base station monitoring signals from a UE, may actively attempt to capture an unencrypted identifier (such as the IMSI / SUPI from the UE). During the attach procedure, the malicious network entity may recognize that the UE is sending an encrypted identifier (e.g., SUCI) and may reject the UE's SUCI with an error code (e.g., an "invalid key" designation) or another similar message indicating that the SUCI authentication failed. By sending an error code, the malicious network entity may impersonate a real cellular wireless network entity because the network-provided encryption key used by the UE to generate the encrypted SUCI may be valid for a limited period of time and then expire. In some cases, such as when the UE is powered off for an extended period of time and the UE misses a network public key update, the network public key used by the UE may be out of date relative to the network secret key used by the home network for authentication. If the UE responds with an unencrypted SUPI instead of an encrypted SUCI, the malicious base station may capture the UE's SUPI, which may invalidate the privacy protection provided by the SUCI.

[0033] If authentication of the wireless network entity fails and the UE has a separate secure connection with a trusted cellular wireless network entity (such as with a trusted server) through a Wi-Fi connection, the UE may obtain an updated network public key and generate a new SUCI for authentication. If authentication of the wireless network entity fails and the UE has only an unauthenticated connection with the wireless network entity, the UE may use a separate fallback encryption key that has been preloaded in the UE to determine whether a message received from the wireless network entity is authentic. A malicious base station may attempt to impersonate a genuine base station by sending a fake network public key to the UE so that the UE sends a SUCI encrypted with the fake network public key to the malicious base station. The malicious base station may then decrypt the SUCI using its own fake network secret key, thereby leaking the unencrypted SUPI to the malicious base station. To address this vulnerability, two levels of encryption keys are used in parallel, where a secondary encryption key, such as a trusted fallback encryption key, is used when an authentication error occurs.

[0034] The trusted fallback encryption key may be initially configured to the UE by a trusted network entity, for example, during an initial configuration process and / or during manufacturing and / or during sales distribution. The fallback encryption key may be rarely used for communications between the UE and the cellular wireless network entity, for example, only to resolve network authentication errors. The fallback encryption key may have a significantly longer lifespan relative to the network public key used to encrypt the SUPI. In some embodiments, the fallback encryption key is securely stored on the eUICC and / or UICC within the UE and cannot be updated, in which case the eUICC must be reprogrammed or the UICC replaced to update the fallback encryption key. In some embodiments, the fallback encryption key is securely stored in the UE and can be updated via a secure connection with a network server.

[0035] The malicious network entity will not be able to decrypt the SUCI without the network secret key and may attempt to obtain the SUPI by impersonating a real cellular wireless network entity by requesting the SUPI directly from the UE and / or by sending a fake network public key to the UE for encrypting the SUPI. The UE may distinguish the malicious network entity from the real cellular wireless network entity by verifying a signature included in a downlink (DL) message from the real cellular wireless network entity that provides the new network public key. The signature is based on a trusted fallback encryption key that the fake base station will not be able to access. In some embodiments, when the SUCI encrypted with the network public key fails authentication, the UE provides the cellular wireless network entity with a SUCI encrypted with the fallback encryption key. In some embodiments, the UE encrypts the SUPI using the new network public key provided by the wireless network entity that the UE is attempting to authenticate and also using the fallback encryption key previously provided by the trusted wireless network entity to form a fallback SUCI. The malicious base station will not be able to decrypt the double encrypted fallback SUCI because the malicious base station cannot access the fallback encryption key, while the real cellular wireless network entity is able to decrypt the double encrypted fallback SUCI. In some embodiments, when the SUCI authentication encrypted with the fallback encryption key fails, the UE stops the attach procedure and provides a denial of service indication.

[0036] In order to uniquely authenticate to the cellular wireless network, the UE sends UL messages that include different one-time SUCIs, corresponding one-time temporary UE public keys, and network public key identifiers. When the network public key is updated, for example, by an over-the-air (OTA) update of a secure connection between the UE and a cellular wireless network server and / or by a downlink (DL) message sent to the UE by a network entity (e.g., by the cellular wireless network entity or by a third-party server providing operator binding updates), the previously generated unused one-time SUCI is discarded and additional new one-time SUCIs are generated based on newly derived encryption keys that are based on the updated network public key and additional one-time temporary UE secret keys. In some embodiments, the fallback encryption key is not required to verify the updated network public key provided via a secure connection from a trusted network entity. In some embodiments, the fallback encryption key is updated by the trusted network entity via a secure connection with the UE (e.g., via an operator binding update). The fallback encryption key can be updated infrequently. In some embodiments, the fallback encryption key is a symmetric key stored in a tamper-resistant hardware secure element (SE) of the UE. In some embodiments, the fallback encryption key provides a higher level of security strength (e.g., 256-bit encryption) than the normal encryption of the SUPI (e.g., 128-bit encryption). In some embodiments, the fallback encryption key is limited to a threshold number of times the UE can use the fallback encryption key. In some embodiments, the fallback encryption key expires after a time period. In some embodiments, the UE encrypts the SUPI based on a combination of an updated network public key and the fallback encryption key to form a fallback SUCI, where the fallback SUCI is used for authentication when the normally encrypted SUCI fails. Both the normally encrypted SUCI and the fallback SUCI can be limited to one-time use for messages sent to a network entity. Using a unique one-time SUCI, the UE maintains privacy from pseudo base stations that attempt to track the UE based on repeated use of encrypted (or unencrypted) identifier values.

[0037] In some embodiments, the UE pre-generates a set of encrypted user identities based on a one-time encryption key derived from a network public key and a one-time temporary user equipment (UE) secret key. When the network public key is updated, the UE regenerates a new one-time encryption key based on the updated network public key and the unused one-time temporary UE secret key. The UE can maintain the network public key in a secure element (SE) based on an over-the-air (OTA) update received from a cellular wireless network entity. The UE can also maintain the network public key in a processing circuit external to the SE based on an operator update binding securely received from a third-party server.

[0038] In some embodiments, a cellular wireless network entity such as an evolved NodeB (eNodeB or eNB) or a next generation node (gNodeB or gNB) is configured with a network public key and a network secret key, while a wireless device such as a user equipment (UE) is also configured with the network public key. The UE generates a set of one or more one-time use temporary UE public key and temporary UE secret key pairs, and derives a set of one or more one-time use encryption keys based on the one-time use temporary UE secret key and the network public key. The UE uses these one-time use encryption keys to encrypt a mobile user identifier of a user permanent identifier (SUPI), such as a mobile user identification number (MSIN) portion of an international mobile subscriber identity (IMSI), to form a set of one-time use user concealed identifiers (SUCI). The UE may store the one-time use encryption key and the associated one-time use temporary UE public key for subsequent authentication with the cellular wireless network entity of the cellular wireless network that provided the network public key. When authentication with the cellular wireless network is required (or other messages requiring the security identity of the UE), such as when initiating a network attachment, the UE sends an uplink (UL) message to the cellular wireless network entity, the UL message including a one-time use SUCI and an associated one-time use temporary UE public key and one of an identifier of a network public key. The cellular wireless network entity may verify the network public key used to encrypt the SUCI, and when the network public key is verified, decrypt the SUCI by using the one-time use temporary UE public key included in the UL message and a network secret key associated with the verified network public key. For subsequent authentication, the UE sends an UL message including a different one-time use SUCI, a corresponding one-time use temporary UE public key, and a network public key identifier.

[0039] When the network public key is updated, for example, by an over-the-air (OTA) update to the UE and / or by a downlink (DL) message sent by a cellular wireless network entity to the UE, a previously generated unused one-time SUCI is discarded. An additional new one-time SUCI is generated based on an encryption key newly derived based on the updated network public key and an additional one-time temporary UE secret key. In some embodiments, the one-time encryption key may be derived as an Advanced Encryption Standard (AES) key. In some embodiments, the UE generates the one-time encryption key based on an Elliptic Curve Diffie-Hellman (ECDH) key agreement protocol.

[0040] The following references Figures 1 to 11 These and other embodiments will be discussed in detail; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting.

[0041] Figure 1 1 is a block diagram of various components of a system 100 configured to implement the various techniques described herein, according to some embodiments. More specifically, Figure 1 A simplified overview of a system 100 is shown, which includes a user equipment (UE) 102, a set of base stations 112-1 through 112-n managed by different mobile network operators (MNOs) 114, and a configuration server 116 in communication with the MNOs 114. The UE 102 may represent a mobile computing device (e.g., of or ), base stations 112-1 to 112-n may represent cellular wireless network entities configured to communicate with UE 102, including evolved NodeBs (eNodeBs or eNBs) and / or next generation NodeBs (gNodeBs or gNBs), and MNO 114 may represent different wireless service providers that provide specific services (e.g., voice and data) to which UE 102 may subscribe.

[0042] like Figure 1 As shown, the UE 102 may include processing circuitry, an embedded universal integrated circuit card (eUICC) 108, and a baseband component 110, the processing circuitry may include a processor 104 and a memory 106. In some embodiments, in addition to or in lieu of the eUICC, the UE 102 includes one or more physical subscriber identity module (SIM) cards (not shown). These components of the UE 102 work together to enable the UE 102 to provide useful features to the user of the UE 102, such as local computing, location-based services, and Internet connectivity. The eUICC 108 may be configured to store multiple electronic SIMs (eSIMs) for accessing different MNOs 114 through base stations 112-1 to 112-n. For example, the eUICC 108 may be configured to store and manage one or more eSIMs for one or more MNOs 114 for different subscriptions associated with the UE 102. In order to be able to access services provided by the MNO, the eSIM may be configured to the eUICC 108. In some embodiments, the eUICC 108 obtains one or more eSIMs (or updates to one or more eSIMs) from one or more associated provisioning servers 116. Note that the provisioning server 116 may be maintained by the manufacturer of the UE 102, the MNO 114, a third-party entity, etc. Communication of eSIM data between the provisioning server 116 and the eUICC 108 (or between the provisioning server 116 and processing circuitry of the UE 102 external to the eUICC 108, such as the processor 104) may use a secure communication channel.

[0043] Figure 2 According to some embodiments, Figure 1 A block diagram of a more detailed view 200 of certain components of a UE 102 is provided. Figure 2 As shown, the processor 104 in conjunction with the memory 106 may implement a main operating system (OS) 202 that is configured to execute application programs 204 (eg, native OS applications and user applications). Figure 2 As shown, the eUICC 108 may be configured to implement an eUICC OS 206 that is configured to manage the hardware resources of the eUICC 108 (e.g., a processor and memory embedded in the eUICC 108). The eUICC OS 206 may also be configured to manage the eSIM 208 stored by the eUICC 108, for example, by enabling, disabling, modifying, or otherwise performing management of the eSIM 208 within the eUICC 108 and providing access to the eSIM 208 to the baseband component 110 to provide access to wireless services to the UE 102. The eUICC 108 OS may include an eSIM manager 210 that may perform management functions for various eSIMs. Figure 2 As shown in the illustration, each eSIM 208 may include a plurality of applets 212 that define the manner in which the eSIM 208 operates. For example, one or more of the applets 212, when implemented by the baseband component 110 and the eUICC 108, may be configured to enable the UE 102 to communicate with the MNO 114 and provide useful features (e.g., phone calls and the Internet) to the user of the UE 102.

[0044] Likewise Figure 2 As shown, the baseband component 110 of the UE 102 may include a baseband OS 214 that is configured to manage the hardware resources (e.g., processor, memory, different radio components, etc.) of the baseband component 110. According to some embodiments, the baseband component 110 may implement a baseband manager 216 that is configured to interact with the eUICC 108 to establish a secure channel with the provisioning server 116 and obtain information (such as eSIM data) from the provisioning server 116 for managing the eSIM 208. The baseband manager 216 may be configured to implement services 218, which represents a collection of software modules that are instantiated by various applets 212 of enabled eSIMs 208 included in the eUICC 108. For example, the services 218 may be configured to manage different connections between the UE 102 and the MNO 114 according to different eSIMs 208 enabled within the eUICC 108.

[0045] Figure 3A block diagram 300 of an exemplary system for capturing a user identity is shown. The system includes a UE 102 including an unencrypted user permanent identifier (SUPI) 304 by which a subscription of a user of the UE 102 can be uniquely identified, the UE 102 communicating with an exemplary cellular wireless network entity, an evolved NodeB (eNodeB) 306. Examples of SUPI 304 include an International Mobile Subscriber Identity (IMSI). The UE 102 and the eNodeB 306 can communicate via a Uu interface, which can be subject to eavesdropping by a third party for some messages or for certain time periods, such as before a secure connection is established between the UE 102 and the eNodeB 306. In some cases, when the eNodeB 306 is connected to a mobility management entity (MME) 308 of the core network via a secure S1-MME interface, and the MME 308 is connected to a home subscriber server (HSS) 310 via a secure S6a interface, the eNodeB 306 may send some messages to and receive some messages from the UE 102 "in the clear." For example, a radio resource control (RRC) paging message sent from the eNodeB 306 to the UE 102 may include the SUPI 304 of the UE 102 in an unprotected manner. Similarly, certain RRC network access stratum (NAS) messages sent from the UE 102 to the eNodeB 306 may also include the SUPI 304 of the UE 102, protecting the SUPI 304 from eavesdroppers without using encryption. Exemplary RRC NAS messages include an RRC Attach Request message, a UE-initiated RRC Detach Request message, and an RRC Identity Response message. A passive eavesdropping entity, such as a passive SUPI catcher 312, may monitor communications sent from the eNodeB 306, such as paging messages, or communications sent from the UE 102, such as attach / detach request messages, and determine the SUPI 304 of the UE 102. Additionally, an active eavesdropping entity, such as an active SUPI catcher 314, may emulate communications from the eNodeB 306 and send a request identity message to the UE 102 and receive an identity response message including the SUPI 304 of the UE 102. The Uu interface between the UE 102 and the eNodeB 306 is susceptible to SUPI exposure due to passive and / or active attacks. The SUPI 304 may be protected from eavesdropping by having the UE 102 and the eNodeB 306 securely encrypt at least a portion of the SUPI 304, such as a mobile subscriber identification number (MSIN), when communicating over an unsecured communication link. Furthermore, where a one-time-use temporary public / secret key pair is used, the SUPI 304 may be protected from future decryption if the previously used secret key is compromised.

[0046] The techniques presented herein may be applied to any message including a globally unique mobile user identifier transmitted between a UE 102 and a cellular wireless network entity, including over an insecure connection susceptible to eavesdropping. Examples of wireless network entities include radio access network entities such as an eNodeB 306 or a next generation NodeB (also referred to as a gNodeB or gNB), or core network entities such as an MME 308, an HSS 310, an authentication server function (AUSF), or an access and mobility function (AMF). The message may include a mobile user identifier, such as an MSIN of a SUPI 304, which may be securely encrypted to protect the privacy of the mobile user identifier. The encrypted version of the SUPI 304 may be referred to as a user concealed identifier (SUCI).

[0047] The active SUPI capturer 314 may also simulate communications from a gNodeB by indicating an authentication failure to the UE 102 in response to the attach procedure request message including the SUCI. If the UE 102 responds to the authentication failure with a second attach procedure request message including the SUPI 304, the active SUPI capturer 314 captures the SUPI 304 from the UE 102. The active SUPI capturer 314 may also simulate communications from the gNodeB by indicating an authentication failure to the UE 102 in response to the attach procedure request message including the SUCI and providing the UE 102 with a pseudo network public key (PKnw*) for encrypting the SUPI 304 to form a SUCI that may be decrypted by the active SUPI capturer 314. As further described herein, the UE 102 may verify the message including the network public key based on a secondary fallback encryption key, which may be a symmetric fallback encryption key K provided to the UE 102 by a trusted source. FB or asymmetric fallback public key PK FB When the message is encrypted with the symmetric fallback key K FB or asymmetric fallback public key PK FB When authenticating, UE 102 may use the network public key provided through the unauthenticated connection. Alternatively or in addition, UE 102 may use the network public key provided through the unauthenticated connection based on the symmetric fallback encryption key K FB Or based on asymmetric fallback public key PK FB To encrypt the SUPI 304 to form a fallback SUCI (SUCI FB ), and use the fallback SUCI FB To retry authentication, the active SUPI capturer 314 will not be able to decrypt the fallback SUCI FB .

[0048] Figure 4A and Figure 4BA flow chart 400 / 450 of a prior art encryption technique for protecting a user identity is shown. For the UE-side encryption flow chart 400, the UE 102 generates a temporary key pair including a temporary UE public key and a temporary UE private key (also referred to as a secret key) that can be provided to another party (such as provided to a cellular wireless network side entity, e.g., eNodeB 306). Based on a key negotiation known to both the UE 102 and the cellular wireless network entity, the UE 102 can generate a shared key (also referred to as a shared secret) based on the temporary UE private key and the network public key (also referred to as the public ECC key of the home public land mobile network or HPLMN). Similarly, the cellular wireless network entity (e.g., eNodeB 306) can generate a shared key based on the key negotiation using the temporary UE public key provided by the UE 102 to the cellular wireless network entity and a network private (secret) key corresponding to the network public key known to the UE 102. The UE 102 and the cellular wireless network entity may use a public key derivation technique to determine a temporary encryption key, which is used for encryption (to form a SUCI from the SUPI 304) and decryption (to restore the SUPI 304 from the SUCI). In some embodiments, the MSIN portion of the SUPI 304 is encrypted, while the MCC / MNC portion of the SUPI 304 may remain unencrypted. Both the UE-side encryption and the network-side encryption may be based on an elliptic curve integrated encryption scheme (ECIES). Figure 4A and Figure 4B The encryption technique shown may be based on a static network public key and a private (secret) key, so if the static network private key is compromised, previous communications including SUPI encrypted using the static network public key may be decrypted. Changing the network public key over time may overcome this drawback.

[0049] Figure 5A An exemplary message exchange 500 for pre-generating an encrypted user identity when transmitting a message to protect the privacy of the user identity according to some embodiments is shown. Initially, the UE 102 may be configured with a network public key (PKnw), and the cellular wireless network entity 516 may be configured with a corresponding network secret key (SKnw) and PKnw. (Note that the term "secret key" is used as a synonym for the term "private key" in this document). PKnw may be transmitted to the UE 102 via a secure communication channel with the cellular wireless network entity, such as between the UE 102 and the configuration server 116, or between the UE 102 and the HSS310, or between the UE 102 and another network-based server, including a third-party server (not shown) in some embodiments. In some embodiments, the UE 102 obtains PKnw in conjunction with the eSIM 208 (or the SIM of the physical UICC).

[0050] At 501, UE 102 may generate a plurality of sets of temporary key pairs, each temporary key pair comprising a temporary UE public key (ePKue) and a corresponding temporary UE secret key (eSKue). UE 102 pre-generates a temporary UE key pair {ePKue, eSKue} to reduce processing time when later authenticating with a wireless network entity using an encrypted version of the user identity (e.g., using SUCI), rather than generating a temporary key pair, an encryption key, and an encrypted identity during authentication with the wireless network. At 502, UE 102 uses the UE-generated eSKue and a public key PKnw provided by the cellular wireless network to derive an encryption key, such as an Advanced Encryption Standard (AES) encryption key (K AES At 503, UE 102 uses the encryption key K AES A mobile user identifier, such as the MSIN portion of the SUPI 304 of the UE 102, is encrypted to generate a set of encrypted user identifiers, i.e., a set of SUCIs from the SUPI 304. The UE 102 may store the encrypted SUCI and the associated temporary public key ePKue for later transmission of a message to the cellular wireless network entity 516, such as during an attachment procedure that requires authentication to the cellular wireless network. In some embodiments, the UE 102 discards the temporary secret key eSKue after encrypting the SUCI. In some embodiments, if the network public key PKnw changes, the UE 102 retains the temporary secret key eSKue for reuse, and once the SUCI is used, the temporary secret key eSKue associated with the SUCI is discarded. In some embodiments, the UE 102 discards the encryption key K after encrypting the SUCI. AES .

[0051] At 504, the UE 102 sends a first uplink (UL) message to the cellular wireless network entity 516, the first UL message including one of the SUCIs, a temporary UE public key ePKue associated with a temporary UE secret key eSKue used to encrypt one of the SUCIs, and a network public key identifier (e.g., PKnw ID) indicating a network public key for key encryption of the SUCI. In some embodiments, the PKnw ID is a hash or count value of PKnw, wherein the cellular wireless network entity 516 can determine that the UE 102 generates the encryption key K AES Which network public key PK is used nw, the SUPI is encrypted using the encryption key to form a SUCI. In some embodiments, each SUCI is used only once, and the UE 102 discards the SUCI and the associated temporary keys, e.g., eSKue and ePKue, after including the SUCI in the UL message.

[0052] At 505, the cellular wireless network entity 516 verifies the network public key PKnw based on the identifier PKnw ID received in the UL message, and when the PKnw is verified, the cellular wireless network entity 516 derives the encryption key K using the temporary UE public key ePKue received from the UE 102 and the network secret key SKnw associated with the network public key PKnw and known to the cellular wireless network entity 516. AES The cellular wireless network entity 516 uses the derived encryption key K AES In some embodiments, the actions performed by the cellular wireless network entity may be performed in a different order. For example, the cellular wireless network entity 516 may use the temporary UE public key ePKue provided by the UE 102 in the UL message and the known valid network secret key SKnw to derive the encryption key K AES , and use the generated encryption key K AES If the SUCI decryption fails to produce a valid SUPI, the cellular wireless network entity 516 may check the network public key identifier PKnw ID to determine whether the UE 102 is using an expired network public key PKnw.

[0053] At 506, the UE 102 sends a second uplink (UL) message to the cellular wireless network entity 516, the second UL message including a second SUCI of the SUCIs indicated as SUIC', a second temporary UE public key indicated as ePKue' associated with a second temporary UE secret key eSKue' used to encrypt the SUPI to generate the second SUCI of the SUCIs, and a network public key identifier, such as PKnw ID. The previous SUCI is used only once, so any damage to the previous SUCI does not affect the security of the current SUCI because each SUCI is encrypted using the one-time temporary UE secret key eSKue.

[0054] At 507, the cellular wireless network entity 516 verifies the PKnw ID, and when the PKnw ID is verified, derives the second encryption key K using the second temporary UE public key ePKue′ and the network secret key SKnw. AES '. Then, the cellular wireless network entity 516 may use K AES'to decrypt the SUCI' to recover the SUPI. The UE 102 may pre-generate encrypted SUCIs and use them for UL messages, as long as the encryption key K is used to generate the encryption key K. AES The network public key PKnw remains valid. If the network public key PKnw is updated, the unused SUCI can be discarded and a new SUCI can be generated based on the updated PKnw, as further described herein.

[0055] Figure 5B An exemplary message exchange 510 for protecting the privacy of a user identity, including updating an encrypted user identity in response to a change in a network public key, is shown according to some embodiments. At 512, UE 102 pregenerates a set of temporary key pairs {ePKue, eSKue}, and at 514, derives an encryption key {K AES At 515, UE 102, for example, by using the encryption key {K AES} and generate a set of encrypted user identifiers {SUCI} from the permanent user identifier SUPI of UE 102 by encrypting the MSIN part of the SUPI with a set of encryption keys K AES The UE 102 may be used to generate a unique encrypted one-time use SUCI from the permanent user identifier SUPI of the UE 102. At 518, the UE 102 transmits an UL message to the cellular wireless network entity 516, such as for authentication to attach to the wireless network or to provide a location area update to the wireless network, wherein the UL message includes one of the encrypted SUCIs together with an identifier of the associated temporary UE public key ePKue and the network public key PKnw. At 520, the cellular wireless network entity 516 verifies the network public key PKnw used by the UE 102 based on the identifier PKnw ID, and when the PKnw is verified, derives the encryption key K using the temporary UE public key ePKue from the UL message and the network secret key SKnw corresponding to the network public key PKnw. AES At 520, the cellular wireless network entity 516 may then use the derived encryption key K AES To decrypt the SUCI from the UL message to obtain the SUPI.

[0056] At 522, the cellular wireless network entity 516 generates a new network key pair {PKnw', SKnw'}. At 524, the cellular wireless network entity 516 sends a downlink (DL) message to the UE 102, which provides the updated network public key PKnw' from the newly generated network key pair {PKnw', SKnw'}. In some embodiments, the cellular wireless network entity 516 pre-generates multiple network key pairs {PKnw, SKnw} and selects new key pairs to replace old key pairs over time. At 525, the UE 102 derives a new encryption key {Knw'} based on the new network public key PKnw' and any unused and / or new temporary secret key {eSKue}. AES In some embodiments, such as when a previously unused temporary secret key {eSKue} is used to generate a previous encryption key {K AES} is discarded, UE 102 derives a new temporary secret key {eSKue'} and uses the new temporary secret key {eSKue'} together with the new network public key PKnw' to generate a new encryption key {K AES At 526, UE 102 discards any unused previously generated encrypted hidden user identifier {SUCI} and uses a new encryption key {K AES '} pre-generates a new set of encrypted user hidden identifiers {SUCI'} from the SUPI of UE 102. The new set of {SUCI'} can replace the previous set of {SUCI} when sending messages to wireless network entities, such as for authentication. At 527, UE 102 sends an UL message to the cellular wireless network entity 516, the UL message including one SUCI' in {SUCI'}, and the encryption key K used to generate the encryption key K. AES '(the encryption key is used to encrypt SUCI') associated with the temporary UE secret key eSKue', and the temporary UE public key ePKue' also used to generate the encryption key K AES At 528, the cellular wireless network entity 516 verifies the network public key PKnw' used by the UE 102 based on the identifier PKnw'ID, and when the PKnw' is verified, uses the temporary UE public key ePKue' extracted from the UL message and the network secret key SKnw' corresponding to the network public key PKnw' to derive the encryption key K AES '. The cellular wireless network entity 516 can then use the derived encryption key K AES 'To decrypt the SUCI from the UL message' to obtain the SUPI.

[0057] Figure 5C Another exemplary message exchange 530 for protecting the privacy of a user identity, including updating an encrypted user identity based on a change in a network public key, is shown according to some embodiments. Figure 5A and Figure 5B As shown, initially, UE 102 may be configured with a network public key (PKnw), and cellular wireless network entity 516 may be configured with a corresponding network secret key (SKnw) and PKnw. At 532, UE 102 pregenerates a set of temporary key pairs {ePKue, eSKue}, and at 534, UE 102 derives an encryption key {K AES At 536, UE 102, for example, by using the encryption key {K AES The MSIN part of the SUPI is encrypted by a set of} and a set of encrypted user identifiers {SUCI} is generated from the permanent user identifier SUPI of the UE 102, where each encryption key K AES The SUCI may be used to generate a unique encrypted one-time use SUCI from the permanent user identifier SUPI of the UE 102. The UE 102 may store the set of {SUCI} for future UL messages. At 538, the cellular wireless network entity 516 generates a new network key pair {PKnw', SKnw'}. However, unlike Figure 5B Different from the new network public key PKnw', the UE 102 may not be aware of the new network public key PKnw'. For example, communication of the new network public key pair PKnw' to the UE 102 may be damaged or otherwise fail, so the UE 102 continues to use the set of {SUCI} generated based on the previous network public key PKnw. At 540, the UE 102 transmits an UL message to the cellular wireless network entity 516, such as for authentication to attach to the wireless network or to provide a location area update to the wireless network, wherein the UL message includes one of the encrypted SUCIs together with the associated temporary UE public key ePKue and the identifier PKnw ID of the network public key PKnw. At 542, the cellular wireless network entity 516 may determine that the network public key identifier PKnw ID is invalid because the most recently generated key pair {PKnw', SKnw'} may replace the use of the previously generated key pair {PKnw, SKnw}. In some embodiments, the key pair is associated with a validity period, which may overlap within a limited time period between successively generated key pairs to allow updates. For Figure 5CIn the message exchange 530, the previously generated key pair {PKnw, SKnw} may no longer be valid, for example, when the validity period has passed. Since the network public key PKnw used by the UE 102 to encrypt the SUCI is no longer valid, the cellular wireless network entity may discard the UL message and provide an update to the UE 102 via a DL message, for example, at 544, the DL message including an indication of the updated network public key PKnw'. In response to receiving the DL message, the UE 102 may recognize that the set of {SUCI} generated based on the previous public key PKnw has expired. At 545, the UE 102 may derive a new encryption key {Knw} based on the updated public key PKnw' and the set of unused and / or new temporary UE secret keys {eSKue}. AES In some embodiments, UE 102 generates a new set of temporary UE secret keys {eSKue'} and associated temporary UE public keys {ePKue'}, and generates a new encryption key {K based on the new set of temporary UE secret keys {eSKue'} and the updated public key PKnw'. AES At 546, UE 102 discards the unused SUCI from the previously generated set of {SUCI} and uses the new encryption key {K AES '} to pre-generate a new set of {SUCI'}. At 547, the UE 102 sends a new UL message, which includes the new encryption user identifier SUCI' together with the associated temporary UE public key ePKue' and the identifier PKnw'ID of the updated public key PKnw'. The new UL message sent at 547 allows the UE 102 to retry to perform an action that previously failed based on the expired network public key PKnw, such as authenticating the cellular wireless network entity 516. At 548, the cellular wireless network entity 516 verifies the public key PKnw' for the UE 102 based on the identifier PKnw'ID obtained from the UL message, and when the PKnw' is verified, derives the encryption key K using the temporary UE public key ePKue' included in the UL message and the currently valid network secret key SKnw' associated with the public key PKnw'. AES The cellular wireless network entity 516 uses the derived encryption key K AES 'To decrypt the SUCI from the UL message' to obtain the unencrypted user identifier SUPI.

[0058] Initial network public keys and updates to network public keys may be provided to UE 102 by different mechanisms. In some embodiments, a cellular wireless network entity updates a network public key maintained by a secure element (SE) of the UE (e.g., eUICC 108) by sending an OTA update to the SE. In some embodiments, a third-party server provides an operator binding update to a processing circuit (e.g., processor 104) external to the SE of the UE, the operator binding update including one or more updated network public keys for one or more cellular wireless networks.

[0059] Figure 5D A method for protecting the privacy of a user's identity (including based on a symmetric fallback encryption key K also used by the user) according to some embodiments is shown. FB Another exemplary message exchange 550 of updating the encrypted user identity with a change of the protected network public key. Initially, the UE 102 may be configured with a network public key (PKnw) and a symmetric fallback encryption key K FB , and the cellular wireless network entity 516 may be pre-configured with the corresponding network secret key (SKnw), network public key PKnw and symmetric fallback encryption key K FB In some embodiments, K FB is a symmetric key that can be used by the cellular wireless network entity 516 and the UE 102 for encryption, decryption and / or signing. At 552, the UE 102 pregenerates a set of temporary key pairs {ePKue, eSKue}, and at 554, the UE 102 derives the encryption key {K AES At 556, UE 102, for example, by using the encryption key {K AES} to generate a set of encrypted user identifiers {SUCI} from the permanent user identifier SUPI of UE 102 by encrypting the MSIN part of the SUPI with a set of encryption keys K AESThe UE 102 may be configured to generate a unique encrypted one-time use SUCI from the permanent user identifier SUPI of the UE 102. The UE 102 may store the set of {SUCI} for future UL messages. At 558, the cellular wireless network entity 516 generates a new network key pair {PKnw', SKnw'}. The UE 102 may be unaware of the new network public key PKnw' generated at 558. For example, communication of the new network public key PKnw' to the UE 102 may be damaged or otherwise fail, such as when the UE 102 is powered off for an extended period of time and does not receive communication of the new network public key PKnw'. Therefore, the UE 102 may continue to use the set of {SUCI} generated based on the previous network public key PKnw, and the UE 102 may be unaware of the new network public key PKnw'. At 559, the UE 102 transmits an UL message to the cellular wireless network entity 516, such as for authentication to attach to the wireless network or to provide a location area update to the wireless network, wherein the UL message includes one of the encrypted SUCIs together with the associated temporary UE public key ePKue and an identifier PKnw ID of the network public key PKnw. At 560, the cellular wireless network entity 516 may determine that the network public key identifier PKnw ID is invalid because the most recently generated key pair {PKnw', SKnw'} may replace the use of the previously generated key pair {PKnw, SKnw}. In some embodiments, the network key pair is associated with a validity period that may overlap within a limited period of time between consecutively generated network key pairs to allow for updates. For Figure 5D Message exchange 550, the previously generated network key pair {PKnw, SKnw} may no longer be valid, for example when the validity period has expired.

[0060] Since the network public key PKnw used by UE 102 to encrypt SUCI is no longer valid, the cellular wireless network entity may provide an update to UE 102, for example, via a DL message at 562, the DL message including an indication of the updated public key PKnw′ and an accompanying variable signature based on the updated public key PKnw′ and the symmetric fallback encryption key K FB The malicious network entity may not have access to the symmetric fallback encryption key K FB, and therefore cannot provide a verifiable signature. At 564, UE 102 may verify the signature to ensure that the updated public key PKnw' can come from a trusted source. When the signature verification of the DL message succeeds, UE 102 may recognize that the set of {SUCI} generated based on the previous public key PKnw has expired. At 566, UE 102 may derive a new encryption key {K based on the updated public key PKnw' and the set of unused and / or new temporary UE secret keys {eSKue}. AES In some embodiments, UE 102 generates a new set of temporary UE secret keys {eSKue'} and associated temporary UE public keys {ePKue'}, and generates a new encryption key {K based on the new set of temporary UE secret keys {eSKus'} and the updated public key PKnw'. AES At 567, UE 102 discards the unused SUCI from the previously generated set of {SUCI} and uses the new encryption key {K AES '} to pre-generate a new set of {SUCI'}. At 568, UE 102 sends a new UL message, which includes the new encryption user identifier SUCI' together with the associated temporary UE public key ePKue' and the identifier PKnw'ID of the updated public key PKnw'. The new UL message sent at 574 allows UE 102 to retry to perform an action that previously failed based on the expired network public key PKnw, such as authenticating the cellular wireless network entity 516. At 569, the cellular wireless network entity 516 verifies the public key PKnw' for UE 102 based on the identifier PKnw'ID obtained from the UL message, and when the PKnw' is verified, derives the encryption key K using the temporary UE public key ePKue' included in the UL message and the currently valid network secret key SKnw' associated with the public key PKnw'. AES The cellular wireless network entity 516 uses the derived encryption key K AES 'To decrypt the SUCI from the UL message' to obtain the unencrypted user identifier SUPI. At 564, the symmetric fallback encryption key K is used FB Verifying the signature ensures that UE 102 does not send a SUCI encrypted with a fake network public key to a malicious network entity.

[0061] Figure 5E Shown as Figure 5D A message exchange sequence 570 of a variation of the message exchange sequence 550 of UE 102 may be configured with a fallback public key PK FB Instead of the symmetric fallback encryption key K FB, and the cellular wireless network entity 516 may be configured with a corresponding fallback secret key SK FB At 572, the cellular wireless network entity 516 may transmit a DL message to the UE 102, the DL message including the updated network public key PKnw' and a signature of the updated network public key PKnw', the signature being based on the fallback secret key SK FB At 574, UE 102 may verify the signature in the DL message to determine whether to trust the cellular wireless network entity 516 and whether to use the updated network public key PKnw' to encrypt the new SUCI'. In addition, Figure 5E The actions and Figure 5D The actions are the same as those described in message exchange sequence 550.

[0062] Fig. 6A A method for protecting the privacy of a user identity (including using a fallback encrypted user identifier SUCI) according to some embodiments is shown. FB 600. The UE 102 may be configured with a network public key PKnw and a symmetric fallback encryption key K FB , and the cellular wireless network entity 516 may be configured with PKnw, the corresponding network secret key SKnw and the symmetric fallback encryption key K FB At 602, UE 102 pregenerates one or more sets of temporary key pairs {ePKue, eSKue}. At 604, UE 102 derives one or more encryption keys {K AES}, each encryption key K AES Based on the network public key PKnw and the temporary secret key eSKue. At 606, UE 102 uses the encryption key {K AES} to generate a set of one or more encrypted identifiers {SUCI}. At 608, UE 102 also encrypts the MSIN portion of the SUPI of UE 102 using a symmetric fallback encryption key K FB The MSIN portion of the SUPI is encrypted to generate a fallback encrypted identifier SUCI FB In some implementations, UE 102 may use a fallback public key PK FB (not shown) to replace the symmetric fallback encryption key K FB For the fallback public key, the cellular wireless network entity 516 has a corresponding fallback secret key SK available for use by the cellular wireless network entity 516. FB (Not shown). Both normal SUCI and fallback SUCI can be stored FBFor subsequent use in messages communicated with the cellular wireless network entity 516. At 610, the UE 102 sends an UL message to the cellular wireless network entity 516, such as during an attach procedure, to provide authentication and / or to provide a location area update. The UL message includes a pre-generated SUCI, an associated temporary UE public key ePKue, and an identifier of the network public key PKnw. At 612, the cellular wireless network entity 516 determines that an authentication error has occurred, for example, based on the expired network public key PKnw used by the UE 102. At 614, the cellular wireless network entity 516 sends a DL message to the UE 102 indicating the authentication error and requesting that the UE 102 recover the authentication error by sending a symmetric fallback encryption key K FB Generated fallback SUCI FB At 616, UE 102 sends a second UL message to cellular wireless network entity 516, the second UL message including the fallback SUCI FB At 618, the cellular wireless network entity determines that UE 102 is authenticated, and at 620, UE 102 and cellular wireless network entity 516 perform a set of actions to establish a secure connection 620 between them. After establishing the secure connection with UE 102, at 622, cellular wireless network entity 516 sends a second DL message including the updated network public key PKnw' to UE 102. At 624, UE 102 uses the updated network public key PKnw' and the newly generated or previously generated and unused temporary UE secret key {eSKue} to derive a new encryption key {K AES At 626, UE 102 discards the previously generated SUCI generated based on the previous network public key PKnw and uses the new encryption key {K AES '} to generate a new set of SUCI'.

[0063] Figure 6B A method for protecting the privacy of user identities (including the use of an asymmetric fallback encryption key pair {PK FB ,SK FB}) message exchange sequence 640. UE 102 may be configured with a network public key PKnw and a fallback public key PK FB , and the cellular wireless network entity 516 may be configured with an updated network public key PKnw', an updated network secret key PKnw' and a fallback secret key SK FB , which corresponds to the fallback public key PK available at UE 102 FBAs previously described herein, the asymmetric network key pair may be updated over time, and in some cases, the UE 102 may miss an update to the asymmetric network key pair, resulting in the UE 102 using an expired (and therefore invalid) network public key to encrypt the SUPI to generate the SUCI to transmit to the cellular wireless network entity 516 for authentication during the attach procedure (or another message for authentication of the UE 102 to be communicated to the cellular wireless network entity 516). FB ,SK FB} is rarely updated (if ever) and only under the condition that the UE 102 is aligned with the cellular wireless network entity 516, under which the asymmetric fallback encryption key is current, so that Figure 6B As shown, the fallback public key PK at UE 102 FB Corresponding to the fallback secret key SK at the cellular wireless network entity 516 FB . The UE 102 may have previously generated a set of one or more encrypted SUCI identifiers based on the network public key PKnw and the temporary UE secret key eSKue, as previously described herein. At 642, the UE 102 sends an UL message to the cellular wireless network entity 516 to provide authentication and / or provide a location area update, such as during an attachment procedure. The UL message includes the SUCI, the temporary UE public key ePKue associated with the temporary UE secret key eSKue used to generate the SUCI, and an identifier of the network public key PKnw. At 644, the cellular wireless network entity 516 determines that an authentication error has occurred, for example based on the expired network public key PKnw used by the UE 102. At 646, the cellular wireless network entity 516 sends a DL message to the UE 102, the DL message including the updated network public key PKnw' and a signature for verifying the updated network public key PKnw', wherein the signature is based on the fallback secret key SK FB At 648, UE 102 may verify the signature in the DL message to determine whether to trust the DL message from the cellular wireless network entity 516 and whether to use the updated network public key PKnw' provided by the cellular wireless network entity 516. The malicious base station will not be able to access the fallback asymmetric key pair {PK FB ,SK FB}, and therefore should not be able to impersonate a genuine base station. When verifying the signature, at 650, UE 102 may derive an updated encryption key K using the updated network public key PKnw' provided in the DL message and the new temporary secret key eSKue' (because the previous temporary secret key eSKue was used to generate the encrypted SUCI that was rejected due to the authentication error). AESAt 652, UE 102 updates the encryption key K, for example by using the updated encryption key K AES 'Encrypt the MSIN portion of the SUPI to generate an updated encrypted SUCI'. At 654, the UE 102 generates an encrypted SUCI by using the fallback public key PK FB SUCI' is further encrypted to generate the fallback encrypted identifier SUCI FB At 656, UE 102 sends a second UL message to cellular wireless network entity 516, the second UL message including the updated network public key identifier PKnw'ID, the fallback SUCI FB and the updated temporary UE public key ePKue'. At 658, the cellular wireless network entity uses the fallback SUCI FB The malicious wireless network entity (e.g., a fake base station) will not be able to access the fallback secret key SK FB , so it will not be possible to decrypt the fallback SUCI FB By utilizing the fallback public key PK FB By encrypting SUCI', UE 102 can ensure that the unencrypted user identity SUPI will not be leaked to malicious wireless network entities, thereby protecting the privacy of the user identity. At 660, UE 102 establishes a secure connection with the cellular wireless network entity 516, and uses the secure connection at 662. In some embodiments, the cellular wireless network entity 516 sends a second DL message to UE 102, and the second DL message includes an updated fallback public key PK FB UE 102 may store the updated fallback public key PK FB ' for later use in case an authentication error occurs during authentication. Fallback public key PK FB The update is optional and may not occur in some cases.

[0064] Fig. 7A and Figure 7B Shows double encryption (and double decryption) of SUPI to generate fallback SUCI FB Flowchart of an exemplary modified encryption technique. Fig. 7A The use of a first temporary encryption key and a second symmetric fallback key K FB Flowchart 700 of an example of double encryption of UE. Both the UE side and the network side have access to the symmetric fallback encryption key K FB Both the UE side and the network side can generate temporary encryption keys. The UE side uses the network public key PKnw and the temporary UE secret key eSKue to generate a temporary encryption key, such as a 128-bit K AESThe temporary encryption key K is used to provide a first encryption of the MSIN portion of the SUPI to form a single encrypted MSIN of the SUCI. FB (It can be a K with a length greater than 128 bits AES A higher protection level encryption key, such as a 256-bit length key, is used to provide a second encryption of the encrypted MSIN portion of the SUCI to generate a fallback SUCI FB The double encrypted MSIN portion of the .

[0065] Figure 7B Shows the use of the first symmetric fallback key K FB Flowchart 705 of an example of double decryption of a temporary encryption key and a second temporary encryption key. The network side can use the symmetric fallback key K FB To roll back SUCI FB The double encrypted MSIN of SUCI is decrypted to generate the single encrypted MSIN of SUCI. The network secret key SKnw corresponds to the network public key PKnw used on the UE side, and the temporary UE public key ePKue is used on the network side to generate a temporary encryption key, such as K AES , the temporary encryption key is used to provide decryption of the single encrypted MSIN portion of the SUCI to generate an unencrypted MSIN portion of the unencrypted SUPI.

[0066] In some embodiments, the network public key PKnw used by UE 102 may be a new network public key provided by cellular wireless network entity 516 before authentication, so UE 102 may not know whether to trust cellular wireless network entity 516. If cellular wireless network entity 516 becomes a malicious network entity such as a fake base station, UE 102 can use the new network public key provided by cellular wireless network entity 516 and the symmetric fallback key Knw previously provided by the trusted network entity. FB Double encryption is performed to prevent unauthorized snooping from obtaining the SUPI. When authentication using double encryption fails, UE 102 may infer that cellular wireless network entity 516 is not trustworthy, stop the attachment process, and discard the new network public key as invalid. When authentication using double encryption succeeds, UE 102 may infer that cellular wireless network entity 516 is trustworthy, and the new network public key provided by the cellular wireless network entity may be valid and may be stored for continued and / or future use.

[0067] Figure 7C and Fig.7D Shows double encryption (and double decryption) of SUPI to generate fallback SUCI FB Flowchart of an additional exemplary modified encryption technique. Fig. 7A and Figure 7BThe modified encryption technique uses a symmetric fallback key K FB , Figure 7C and Fig.7D The technique shown in can use an asymmetric fallback key pair {PK FB ,SK FB}. Figure 7C The first temporary encryption key (key 1) generated based on the network public key PKnw and the temporary UE secret key eSKue and the asymmetric fallback public key PK FB Flowchart 710 of an example of double encryption of a second temporary encryption key (Key 2) generated using a temporary UE secret key eSKue. The UE side has access to an asymmetric fallback public key PK FB , and the network side has access to the corresponding asymmetric fallback secret key SK FB . The UE side provides a temporary UE public key ePKue to the network side, and the network side provides a network public key PKnw to the UE side. Both the UE side and the network side can generate the same set of temporary encryption keys {Key 1, Key 2}. The first temporary encryption key (Key 1) based on the network public key PKnw is used to provide a first encryption of the MSIN part of the SUPI to form a single encrypted MSIN of the SUCI. Based on the asymmetric fallback public key PK FB The second temporary encryption key (Key 2) is used to provide a second encryption of the encrypted MSIN portion of the SUCI to generate a fallback SUCI FB The double encrypted MSIN portion of the present invention is a double encrypted MSIN portion of the present invention. In some embodiments, the first encryption key (Key 1) and the second encryption key (Key 2) have different encryption strengths, for example, the first encryption key (Key 1) may be a 128-bit key, and the second encryption key (Key 2) may be a 256-bit key. In some embodiments, the first encryption key (Key 1) and the second encryption key (Key 2) may have similar encryption strengths, for example, both the first encryption key and the second encryption key may be 128-bit keys. For the first temporary encryption key (Key 1) and the second temporary encryption key (Key 2), the key generation algorithm (e.g., ECDH key generation) used to generate the temporary encryption key may also be different, or may be the same.

[0068] Fig.7D The use of (i) an asymmetric fallback key SK for the first decryption is shown FB Flowchart 715 of an example of double decryption of (i) a second temporary encryption key (key 2) based on the network key SKnw and (ii) a first temporary encryption key (key 1) based on the network key SKnw for the second decryption. The network side may use the second temporary encryption key (key 2) to perform a fallback SUCI FBThe network side may then decrypt the double encrypted MSIN part of the SUCI to generate a single encrypted MSIN part of the SUCI using the first temporary encryption key (Key 1) to generate an unencrypted MSIN part of the SUPI. The network side may generate a temporary key using a network secret key SKnw corresponding to the network public key PKnw used by the UE side and a temporary UE public key ePKue provided by the UE side to the network side.

[0069] based on Figure 7C and Fig.7D The double encryption of flowcharts 710 and 715 provides Fig. 7A and Figure 7B Similar beneficial effects can be achieved by flowcharts 700 and 705: authentication failure may indicate that the new network public key provided by the network side (e.g., cellular wireless network entity 516) is not trusted and should not be used, while authentication success may indicate that the new network public key is trusted, may be valid and can be stored for continued and / or future use.

[0070] Fig. 7E and Figure 7F Shown is the encryption (and decryption) of the SUPI to generate the fallback SUCI FB Flowchart of an additional exemplary modified encryption technique. FIG. 7C to FIG. 7D As with the modified encryption technique shown in Fig. 7E and Figure 7F The technique shown in can use an asymmetric fallback key pair {PK FB ,SK FB}. Fig. 7E A flowchart 720 is shown of UE-side encryption using a fallback public key PK FB The network public key PKnw and the temporary UE secret key eSKue are combined to generate a temporary encryption key to encrypt the MSIN part of the SUPI, thereby generating the encrypted MSIN part of the SUCI. The key agreement known to both the UE side and the network side can combine several keys to generate one or more shared keys that can be used to derive the temporary encryption key.

[0071] Figure 7F A flowchart 725 is shown of the corresponding network-side decryption, which uses the fallback secret key SK FB (corresponding to the fallback public key PK used on the UE side FB), network secret key SKnw (corresponding to the network public key PKnw used on the UE side) and temporary UE public key ePKue (corresponding to the temporary UE secret key eSKue used on the UE side) are used to generate a set of shared keys and derive a temporary encryption key, which is used to decrypt the encrypted MSIN part of SUCI to obtain the unencrypted MSIN of SUPI. Fallback secret key SK FB The encrypted SUCI may not be known to a malicious wireless network entity and therefore cannot be decrypted to generate an unencrypted SUPI.

[0072] based on Fig. 7E and Figure 7F The double encryption of flowcharts 720 and 725 provides Fig. 7A , Figure 7B , Figure 7C and Fig.7D The flowchart has similar beneficial effects: authentication failure may indicate that the new network public key provided by the network side (e.g., the cellular wireless network entity 516) is not trusted and should not be used, while authentication success may indicate that the new network public key is trusted, may be valid and can be stored for continued and / or future use.

[0073] Figure 7G and Figure 7H Shown is the encryption (and decryption) of the SUPI to generate the fallback SUCI FB Flowchart of an additional exemplary modified encryption technique. Figure 7C , 7D , Fig. 7E and Figure 7F Like the modified encryption technique shown in , the techniques shown in 7G and 7H may use an asymmetric fallback key pair {PK FB ,SK FB}. Figure 7G A flowchart 730 is shown of UE-side encryption using a fallback public key PK FB The network public key PKnw and the temporary UE secret key eSKue are combined to generate a temporary encryption key (key 3) to encrypt the MSIN part of the SUPI, thereby generating the encrypted MSIN part of the SUCI. On the UE side, the network public key PKnw that can be provided by the network side to the UE side and the temporary UE secret key SKue that can be generated in advance or in real time by the UE side are input into the first ECDH key generation block to generate the first temporary encryption key (key 1). In addition, on the UE side, the fallback public key PK that can be previously provided by the trusted entity on the network side to the UE side is FBThe temporary UE secret key SKue is input to the second ECDH key generation block to generate a second temporary encryption key (Key 2). In some embodiments, the first ECDH key generation block and the second ECDH key generation block implement the same algorithm for key generation. In some embodiments, the first ECDH key generation block and the second ECDH key generation block implement different algorithms for key generation. The first temporary encryption key (Key 1) and the second temporary encryption key (Key 2) are input to the key derivation block to generate a temporary encryption key (Key 3), which is used to encrypt the unencrypted MSIN portion of the SUPI to generate the encrypted MSIN portion of the SUCI.

[0074] Figure 7H A flowchart 735 is shown of the corresponding network-side decryption, which uses the fallback secret key SK FB (corresponding to the fallback public key PK used on the UE side FB ), network secret key SKnw (corresponding to the network public key PKnw used on the UE side) and temporary UE public key ePKue (corresponding to the temporary UE secret key eSKue used on the UE side) to generate a set of temporary encryption keys (key 1 and key 2) and then derive a temporary encryption key (key 3), and use key 3 to decrypt the encrypted MSIN part of SUCI to obtain the unencrypted MSIN of SUPI. Fallback secret key SK FB The malicious wireless network entity may not know about it and therefore cannot decrypt the SUCI to obtain the SUPI.

[0075] based on Figure 7G and Figure 7H Flowcharts 730 and 735 of the invention provide a single encryption using multiple combined encryption keys. Fig. 7A , Figure 7B , Figure 7C , Fig.7D , Fig. 7E and Figure 7F The flowchart has similar beneficial effects: authentication failure may indicate that the new network public key provided by the network side (e.g., the cellular wireless network entity 516) is not trusted and should not be used, while authentication success may indicate that the new network public key is trusted, may be valid and can be stored for continued and / or future use.

[0076] Fig.7I A method for protecting the privacy of user identities (including the use of a fallback asymmetric encryption key pair {PK FB ,SK FB}) another message exchange sequence 770. The UE 102 may be configured with a network public key PKnw and a fallback public key PK FB, and the cellular wireless network entity 516 may be configured with an updated network public key PKnw', an updated network secret key PKnw' and a fallback secret key SK FB , which corresponds to the fallback public key PK available at UE 102 FB As previously described, the asymmetric network key pair may be updated over time, and in some cases, the UE 102 may miss an update to the asymmetric network key pair, resulting in the UE 102 using an expired (and therefore invalid) network public key to encrypt the SUPI to generate the SUCI for transmission to the cellular wireless network entity 516 for authentication during the attach procedure (or another message for authentication of the UE 102 is communicated to the cellular wireless network entity 516). The UE 102 may have previously generated a set of one or more encrypted SUCI identifiers based on the network public key PKnw and the temporary UE secret key eSKue. At 772, the UE 102 sends a first UL message to the cellular wireless network entity 516, such as during the attach procedure, to provide authentication and / or provide a location area update. The first UL message includes the SUCI, the temporary UE public key ePKue associated with the temporary UE secret key eSKue used to generate the SUCI, and an identifier PKnw ID of the network public key PKnw. At 774, the cellular wireless network entity 516 determines that an authentication error has occurred, for example, based on the expired network public key PKnw used by the UE 102. At 776, the cellular wireless network entity 516 sends a DL message to the UE 102, the DL message including the updated network public key PKnw' and a signature for verifying the updated network public key PKnw', wherein the signature is based on the fallback secret key SK FB At 778, UE 102 verifies the signature in the DL message to determine whether to trust the DL message from the cellular wireless network entity 516 and whether to use the updated network public key PKnw' provided by the cellular wireless network entity 516. The malicious base station will not be able to access the fallback asymmetric encryption key pair {PK FB ,SK FB}, and therefore should not be able to impersonate a genuine base station. When verifying the signature, at 780, UE 102 uses the updated network public key PKnw' provided in the DL message, the new temporary key eSKue' (because the previous temporary key eSKue has been used to generate an encrypted SUCI that was rejected due to an authentication error), and the fallback public key PK FB To derive the updated encryption key K AES '. Examples of using three keys to generate temporary encryption keys are given in 7E and Fig.7I At 782, UE 102, for example, by using the updated encryption key K AES'Encrypt the MSIN portion of the SUPI to generate a fallback encrypted identifier SUCI FB At 784, UE 102 sends a second UL message to cellular wireless network entity 516, the second UL message including updated network public key identifier PKnw'ID, fallback SUCI FB and the updated temporary UE public key ePKue'. At 786, the cellular wireless network entity 516 uses the fallback SUCI FB The malicious wireless network entity (eg, a fake base station) will not be able to access the corresponding fallback secret key SK FB , so it will not be possible to decrypt the fallback SUCI FB Using a fallback asymmetric key pair {PK FB ,SK FB The additional encryption of} ensures that the unencrypted user identity SUPI is not leaked to malicious wireless network entities, thereby protecting the privacy of the user identity. At 788, UE 102 establishes a secure connection with the cellular wireless network entity 516, and uses the secure connection at 790. In some embodiments, the cellular wireless network entity 516 sends a second DL message to UE 102, which includes an updated fallback public key PK FB UE 102 may store the updated fallback public key PK FB ' for later use if an authentication error occurs during authentication.

[0077] Figure 8 A flowchart 800 is shown of an exemplary sequence of actions performed by a wireless device (e.g., UE 102) to protect the privacy of a user identity during a network attachment process. At 802, UE 102 initiates a network attachment process with a cellular wireless network entity 516, which may not be trusted by UE 102 until authentication is successful. At 804, UE 102 transmits an encrypted identifier (e.g., SUCI) to cellular wireless network entity 516. In some embodiments, SUCI is generated using an unencrypted identifier (e.g., SUPI), a network public key PKnw, and a temporary UE secret key eSKue based on an elliptic curve integrated encryption scheme (ECIES). At 806, UE 102 determines whether authentication with cellular wireless network entity 516 is successful or failed, for example based on a message received from cellular wireless network entity 516. When authentication is successful, at 808, UE 102 may continue the network attachment process to establish a secure connection with cellular wireless network entity 516. When authentication fails, at 810, UE 102 may retry authentication by transmitting a second message to cellular wireless network entity 516, the second message including a fallback SUCI. FB , the fallback SUCIFB Generated based on a combination of: (i) an unencrypted identifier, such as SUPI, and (ii) a fallback encryption key K FB Or fallback public key PK FB , and (iii) a different temporary UE secret key eSKue'. At 812, UE 102 determines whether authentication with cellular wireless network entity 516 succeeds or fails, for example, based on a message received from cellular wireless network entity 516. When authentication succeeds, at 808, UE 102 may continue a network attachment procedure to establish a secure connection with cellular wireless network entity 516. When authentication fails, at 814, UE 102 may stop the network attachment procedure and report a service denial error, for example, by providing an indication on a display of UE 102.

[0078] In some embodiments, the UE 102 pre-generates a fallback SUCI before initiating the attach procedure. FB , for example, Fig. 6A In some embodiments, the UE 102 generates a fallback SUCI after initiating the attach procedure. FB , for example, Figure 6B 654 and Fig. 7E In some embodiments, UE 102 uses the symmetric fallback key K FB To generate fallback SUCI FB , for example, Fig. 6A 608 of them and Fig. 7A In some embodiments, UE 102 uses the fallback public key PK FB To generate fallback SUCI FB , for example, Figure 6B 654 of them, Figure 7C , Fig. 7E , Figure 7G as well as Fig.7I As shown in 780 / 782 of FIG. FB ,SK FB}'s corresponding fallback secret key SK FB Known only by trusted cellular wireless network entities (e.g., genuine base stations) and not by malicious wireless network entities (e.g., fake base stations). Encrypting SUPI to form a fallback encrypted SUCI FB And use fallback SUCI in case of authentication error FB Attacks from malicious wireless entities that attempt to decrypt the SUCI received from the UE 102 to obtain the unencrypted SUPI may be prevented.

[0079] Fig. 9A block diagram 900 illustrates an example of overlapping time periods for using keys including, for example, a network public key PKnw, a symmetric fallback encryption key K FB and / or asymmetric fallback encryption key pair {PK FB ,SK FB In some embodiments, the network public key PKnw has a lifetime that is significantly shorter than the symmetric fallback encryption key K FB and / or asymmetric fallback encryption key pair {PK FB ,SK FB At the time indicated by 902, a first network public key K1 is established for use during the time period indicated as the lifetime of K1. When changing between different network public keys, such as when updating network public key K1 to K2, the lifetime of the previous network public key may overlap with the lifetime of the latest network public key. For example, at the time indicated by 904, a second network public key K2 is established for use during the time period indicated as the lifetime of K2. Fig. 9 As shown, the lifetimes of K1 and K2 span an overlapping time period 912, wherein both the first key K1 and the second key K2 can be actively used before the first key K1 expires at time 906. The overlap allows the UE 102 to switch from using the first key K1 to using the second key K2 using a variable time. Similarly, when the third key K3 is established at time 908, the lifetime of the third key K3 overlaps with the time period 914 until the second key K2 expires at time 910. In some embodiments, the network key pair may be updated by the cellular wireless network entity 516 using an over-the-air (OTA) secure connection between the cellular wireless network entity 516 and the UE 102. Similarly, in some embodiments, the network key pair may overlap in time to allow for unexpected interruptions in the transmission of the updated network public key from the cellular wireless network entity 516 to the UE 102, and to allow for delays in updating the network public key at the UE 102. Robust key rotation may be achieved by keeping both the old key and the new key alive (e.g., actively used by the UE 102) during the overlapping lifetimes. As discussed herein, some UL messages from the UE 102 may include a key ID to indicate the network public key used by the UE 102 when deriving encryption keys with which to encrypt a mobile user identifier (such as the MSIN of the IMSI of the UE 102) to form a SUCI from a SUPI. In some embodiments, the symmetric fallback encryption key K FB and / or fallback public key PK FBThe symmetric fallback encryption key K may be provided by the cellular wireless network entity 516 to the UE 102 when trusted, such as via a secure connection established between the UE 102 and the cellular wireless network entity 516 after successful authentication. FB and / or asymmetric fallback public key PK FB It can only be updated by a trusted server of a wireless network service provider (e.g., an MNO) or a third-party entity delegated by the MNO for updates. In some embodiments, the continuous symmetric fallback encryption key K FB The overlap period between is minimal, or the previous symmetric fallback encryption key K FB With the updated symmetric fallback encryption key K FB There is no overlap between them. In some embodiments, the continuous asymmetric fallback encryption key pair {PK FB ,SK FB} is minimal, or the previous asymmetric encryption key pair {PK FB ,SK FB} and the updated asymmetric encryption key pair {PK FB ',SK FB There is no overlap between '}.

[0080] Fig. 10A Flowchart 1000 illustrates a set of exemplary actions performed by a wireless device (e.g., UE 102) to protect the privacy of a user identity. At 1002, UE 102 initiates an attach procedure with cellular wireless network entity 516. At 1004, UE 102 sends a first uplink (UL) message including a user concealed identifier (SUCI) to cellular wireless network entity 516. At 1006, UE 102 receives an authentication failure indication from cellular wireless network entity 516. In some embodiments, the authentication failure indication includes a fallback SUCI. FB to retry the authentication request. In some embodiments, the authentication failure indication includes an updated network public key PKnw'. In some embodiments, the authentication failure indication includes a symmetric fallback key K FB or asymmetric fallback secret key SK FB 1008, UE 102 sends a fallback SUCI to cellular wireless network entity 516. FB In some embodiments, UE 102 pre-generates a fallback SUCI before initiating the attach procedure. FB In some embodiments, the UE 102 generates a fallback SUCI during the attach procedure. FBIn some embodiments, UE 102 uses a symmetric fallback key K FB or asymmetric fallback public key PK FB To generate fallback SUCI FB In some embodiments, when authenticated by UE 102, UE 102 generates a fallback SUCI using the updated network public key PKnw′ and, for example, based on the accompanying signature. FB At 1010, the UE receives an additional authentication failure indication from the cellular wireless network entity 516. FB Having failed authentication twice, the UE 102 may conclude that the cellular wireless network entity 516 may not be trusted and terminate the attach procedure with the cellular wireless network entity 516 at 1012. At 1014, the UE 102 may provide an error condition indication, such as a service denial error.

[0081] Fig. 10B and Fig. 10C Flowcharts 1020 and 1040 illustrate another set of exemplary actions performed by a wireless device (e.g., UE 102) to protect the privacy of a user identity. At 1022, UE 102 initiates an attach procedure with cellular wireless network entity 516. At 1024, UE sends a first uplink (UL) message to cellular wireless network entity 516, the first UL message including a user hidden identifier (SUCI) encrypted using an encryption key based on a network public key PKnw. At 1026, UE 102 receives an authentication failure indication from cellular wireless network entity 516, the authentication failure indication including an authentication failure indication encrypted using a symmetric fallback key K FB Or use an asymmetric fallback secret key SK FB At 1028, UE 102 uses the asymmetric fallback secret key SK FB The symmetric fallback key PK FB or asymmetric fallback public key SK FB to verify the updated network public key PKnw'. When the verification is successful, at 1030, UE 102 generates a new public key based at least in part on the updated PKnw' and the symmetric fallback key K FB or asymmetric fallback public key PK FB At 1032, UE 102 sends a second UL message including the updated SUCI' to cellular wireless network entity 516. At 1034, UE 102 receives an authentication success indication from cellular wireless network entity 516. At 1036, UE 102 establishes a secure connection with the cellular wireless network entity. At 1038, in some embodiments, UE 102 receives an updated symmetric fallback key K via the secure connection.FB ' or a newer asymmetric fallback public key PK FB '.

[0082] Fig.11 A detailed view of a representative computing device 1100 that can be used to implement the various methods described herein is shown in accordance with some embodiments. In particular, the detailed view shows that a computer system that can be included in Figure 1 The various components in the UE 102 are shown. Fig.11 As shown, the computing device 1100 may include a processor 1102 representing a microprocessor or controller for controlling the overall operation of the computing device 1100. The computing device 1100 may also include a user input device 1108 that allows a user of the computing device 1100 to interact with the computing device 1100. For example, the user input device 1108 may take a variety of forms, such as buttons, keypads, dials, touch screens, audio input interfaces, visual / image capture input interfaces, input in the form of sensor data, etc. Further, the computing device 1100 may include a display 1110 (screen display) that can be controlled by the processor 1102 to display information to the user. The data bus 1116 can facilitate data transfer between at least the storage device 1140, the processor 1102, and the controller 1113. The controller 1113 can be used to interact with and control different equipment through the equipment control bus 1114. The computing device 1100 may also include a network / bus interface 1111 coupled to the data link 1112. In the case of a wireless connection, the network / bus interface 1111 may include a wireless transceiver.

[0083] The computing device 1100 also includes a storage device 1140 (which may include a single disk or multiple disks, such as a hard drive), and includes a storage management module that manages one or more partitions within the storage device 1140. In some embodiments, the storage device 1140 may include flash memory, semiconductor (solid-state) memory, etc. The computing device 1100 may also include a random access memory (RAM) 1120 and a read-only memory (ROM) 1122. The ROM 1122 may store programs, utilities, or processes to be executed in a non-volatile manner. The RAM 1120 may provide volatile data storage and store instructions related to the operation of the computing device 1100. The computing device 1100 may also include a secure element (SE) 1150, which may represent the eUICC 108 of the UE 102.

[0084] Various aspects, embodiments, specific implementations or features of the embodiments may be used individually or in any combination. Various aspects of the embodiments may be implemented by software, hardware, or a combination of hardware and software. The embodiments may also be implemented as computer readable code on a non-transitory computer readable medium. A non-transitory computer readable medium is any data storage device that can store data that can then be read by a computer system. Examples of the non-transitory computer readable medium include read-only memory, random access memory, CD-ROM, DVD, magnetic tape, hard disk drive, solid state drive, and optical data storage device.

[0085] For the purpose of illustration, the foregoing description uses specific nomenclature to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments can be practiced without specific details. Therefore, the foregoing description of specific embodiments is presented for the purpose of illustration and description. The foregoing description is not intended to be exhaustive or to limit the embodiments described to the precise form disclosed. It will be apparent to those of ordinary skill in the art that, in view of the above teachings, many modifications and variations are feasible.

Claims

1. A user equipment UE, the UE comprising: wireless circuitry configurable for wireless communication with a wireless network; and a processing circuit, the processing circuit being communicatively coupled to the wireless circuit and comprising a processor and a memory, the memory storing instructions that, when executed by the processor, cause the UE to perform a method for protecting the privacy of a user identity included in the UE, the method comprising: Initiating an attachment procedure with a cellular wireless network entity; Sending a first uplink (UL) message to the cellular wireless network entity, wherein the first UL message includes a hidden user identifier (SUCI) generated by encrypting a user permanent identifier (SUPI); receiving an authentication failure indication from the cellular wireless network entity; Sending a fallback SUCI to the cellular wireless network entity FB The second UL message; When receiving an authentication success indication from the cellular wireless network entity in response to the second UL message, establishing a secure connection with the cellular wireless network entity; and when a second authentication failure indication is received from the cellular wireless network entity in response to the second UL message, terminating the attach procedure with the cellular wireless network entity, wherein the symmetric fallback encryption key K configured to the UE by a network entity of the cellular wireless network is at least partially based on FB or asymmetric fallback public key PK FB Encrypting the SUPI to generate the SUCI FB .

2. The UE according to claim 1, wherein the method performed by the UE further comprises: By the UE: When the second authentication failure indication is received, a service rejection error indication is provided on a display of the UE.

3. The UE according to claim 1, wherein the UE generates the SUCI before initiating the attach procedure with the cellular wireless network entity. FB .

4. The UE according to claim 1, wherein the UE generates the SUCI based on information included in the authentication failure indication during the attach procedure. FB .

5. The UE according to claim 1, wherein the authentication failure indication comprises a request for the UE to use the SUCI FB Retry authentication message.

6. The UE according to claim 1, wherein: The SUCI is encrypted with an encryption key, wherein the encryption key is derived from a network public key PKnw provided by the cellular wireless network and a temporary UE secret key eSKue generated by the UE; The authentication failure indication includes using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB Signed updated network public key PKnw'; and The SUCI FB It is further encrypted using the updated network public key PKnw'.

7. The UE according to claim 6, wherein the method performed by the UE further comprises: By the UE: In generating the SUCI FB Before, using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB To verify the updated network public key PKnw'.

8. The UE according to claim 1, wherein the method performed by the UE further comprises: After establishing the secure connection with the cellular wireless network entity, the UE: receiving a downlink DL message from a network-based server, the DL message including an updated network public key PKnw'; discarding the SUCI from a storage medium of the UE; The new encryption key K is derived based on the updated network public key PKnw' and the newly generated temporary UE secret key eSKue' AES '; Based on the SUPI and the new encryption key K AES 'to generate new SUCI'; as well as The new SUCI′ is stored in the storage medium of the UE.

9. The UE of claim 8, wherein the DL message comprises an operator binding update for a plurality of mobile network operators (MNOs), the operator binding update comprising the updated PKnw' for a wireless network of at least one of the MNOs.

10. The UE of claim 9, wherein the network-based server comprises a third-party server maintained by an entity external to the MNO.

11. The UE of claim 8, wherein the DL message comprises an over-the-air OTA update from a configuration server of an MNO, the DL message being provided to an embedded universal integrated circuit card (eUICC) or a physical subscriber identity module (SIM) card of the UE.

12. The UE according to claim 1, wherein the first UL message further comprises a key identifier ID, wherein the key ID indicates to the cellular wireless network entity which network public key PKnw the UE uses to derive the encryption key K for encrypting the SUCI. AES .

13. The UE according to claim 12, wherein the key ID comprises PKnw, a hash of PKnw, or a count value.

14. The UE according to claim 1, wherein the cellular wireless network entity comprises an evolved NodeB (eNodeB) or a next generation NodeB (gNB).

15. The UE according to claim 1, wherein: The SUPI comprises an International Mobile Subscriber Identity (IMSI); and The SUCI includes an encrypted version of the Mobile Subscriber Identification Number (MSIN) of the IMSI.

16. An apparatus configured to operate in a user equipment (UE), the apparatus comprising a processor and a memory, the memory storing instructions which, when executed by the processor, cause the UE to perform a method for protecting the privacy of a user identity included in the UE, the method comprising: Initiating an attach procedure with a cellular wireless network entity; Sending a first uplink (UL) message to the cellular wireless network entity, wherein the first UL message includes a hidden user identifier (SUCI) generated by encrypting a user permanent identifier (SUPI); receiving an authentication failure indication from the cellular wireless network entity; Sending a fallback SUCI to the cellular wireless network entity FB The second UL message; When receiving an authentication success indication from the cellular wireless network entity in response to the second UL message, establishing a secure connection with the cellular wireless network entity; as well as when a second authentication failure indication is received from the cellular wireless network entity in response to the second UL message, terminating the attach procedure with the cellular wireless network entity, wherein the symmetric fallback encryption key K configured to the UE by a network entity of the cellular wireless network is at least partially based on FB or asymmetric fallback public key PK FB Encrypting the SUPI to generate the SUCI FB .

17. The device according to claim 16, wherein: The SUCI is encrypted with an encryption key, wherein the encryption key is derived from a network public key PKnw provided by the cellular wireless network and a temporary UE secret key eSKue generated by the UE; The authentication failure indication includes using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB Signed updated network public key PKnw'; and The SUCI FB It is further encrypted using the updated network public key PKnw'.

18. The apparatus of claim 16, wherein the method performed by the UE further comprises: After establishing the secure connection with the cellular wireless network entity, the UE: receiving a downlink DL message from a network-based server, the DL message including an updated network public key PKnw'; discarding the SUCI from a storage medium of the UE; The new encryption key K is derived based on the updated network public key PKnw' and the newly generated temporary UE secret key eSKue' AES '; Based on the SUPI and the new encryption key K AES 'to generate new SUCI'; as well as storing the new SUCI′ in the storage medium of the UE.

19. The apparatus of claim 18, wherein the DL message comprises an operator binding update for a plurality of mobile network operators (MNOs), the operator binding update comprising the updated PKnw' for a wireless network of at least one of the MNOs.

20. The apparatus of claim 16, wherein the first UL message further comprises a key identifier (ID), the key ID indicating to the cellular wireless network entity which network public key PKnw the UE uses to derive the encryption key K for encrypting the SUCI. AES .

21. A cellular wireless network entity, comprising: a wireless circuit configurable for wireless communication with a user equipment UE; and a processing circuit, the processing circuit being communicatively coupled to the wireless circuit and comprising a processor and a memory, the memory storing instructions that, when executed by the processor, cause the cellular wireless network entity to perform a method for protecting the privacy of a user identity included in the UE, the method comprising: receiving a first uplink (UL) message from the UE, the first UL message including a user hidden identifier (SUCI) generated by encrypting a user permanent identifier (SUPI) based on a network public key (PKnw) and an identifier of PKnw; determining an authentication error of the UE based on expiration of a PKnw used by the UE; In response to the first UL message, a first downlink DL message is sent to the UE, wherein the first DL message includes an authentication failure indication and a fallback SUCI, that is, a SUCI. FB Requests; receiving, from the UE, the SUCI FB The second UL message; determining successful authentication based at least in part on the second UL message; sending, in response to the second UL message, a second DL message including an authentication success indication from the cellular wireless network entity to the UE; and establishing a secure connection with the UE after successful authentication; The UE uses a symmetric fallback encryption key K configured to the UE by a network entity of the cellular wireless network at least in part. FB or asymmetric fallback public key PK FB Encrypting the SUPI to generate the SUCI FB .

22. The cellular wireless network entity according to claim 21, wherein: The SUCI is encrypted by the UE using an encryption key, wherein the encryption key is derived from a network public key PKnw previously provided to the UE by the cellular wireless network and a temporary UE secret key eSKue generated by the UE; The authentication failure indication includes using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB Signed updated network public key PKnw'; and The SUCI FB It is further encrypted using the updated network public key PKnw'.

23. The cellular wireless network entity according to claim 21, wherein the identifier of PKnw included in the first UL message is a key identifier ID, wherein the key ID indicates to the cellular wireless network entity which network public key PKnw the UE uses to derive the encryption key K for encrypting the SUCI. AES .

24. The cellular wireless network entity according to claim 23, wherein the key ID comprises PKnw, a hash of PKnw or a count value.

25. The cellular wireless network entity of claim 21, wherein the authentication failure indication comprises a request for the UE to use the SUCI FB Retry authentication message.

26. A method for protecting the privacy of a user identity included in a user equipment UE, the method comprising: By the UE: Initiating an attach procedure with a cellular wireless network entity; Sending a first uplink (UL) message to the cellular wireless network entity, wherein the first UL message includes a hidden user identifier (SUCI) generated by encrypting a user permanent identifier (SUPI); receiving an authentication failure indication from the cellular wireless network entity; Sending a fallback SUCI to the cellular wireless network entity FB The second UL message; When receiving an authentication success indication from the cellular wireless network entity in response to the second UL message, establishing a secure connection with the cellular wireless network entity; and when a second authentication failure indication is received from the cellular wireless network entity in response to the second UL message, terminating the attach procedure with the cellular wireless network entity, wherein the symmetric fallback encryption key K configured to the UE by a network entity of the cellular wireless network is at least partially based on FB or asymmetric fallback public key PK FB Encrypting the SUPI to generate the SUCI FB .

27. The method according to claim 26, wherein the method further comprises: By the UE: When the second authentication failure indication is received, a service rejection error indication is provided on a display of the UE.

28. The method of claim 26, wherein the UE generates the SUCI before initiating the attach procedure with the cellular wireless network entity. FB .

29. The method of claim 26, wherein the UE generates the SUCI based on information included in the authentication failure indication during the attach procedure. FB .

30. The method of claim 26, wherein the authentication failure indication comprises a request for the UE to use the SUCI FB Retry authentication message.

31. The method of claim 26, wherein: The SUCI is encrypted with an encryption key, wherein the encryption key is derived from a network public key PKnw provided by the cellular wireless network and a temporary UE secret key eSKue generated by the UE; The authentication failure indication includes using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB Signed updated network public key PKnw'; and The SUCI FB It is further encrypted using the updated network public key PKnw'.

32. The method of claim 31, wherein the method further comprises: By the UE: In generating the SUCI FB Before, using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB To verify the updated network public key PKnw'.

33. The method of claim 26, wherein the method further comprises: After establishing the secure connection with the cellular wireless network entity, the UE: receiving a downlink DL message from a network-based server, the DL message including an updated network public key PKnw'; discarding the SUCI from a storage medium of the UE; The new encryption key K is derived based on the updated network public key PKnw' and the newly generated temporary UE secret key eSKue' AES '; Based on the SUPI and the new encryption key K AES 'to generate new SUCI'; as well as storing the new SUCI′ in the storage medium of the UE.

34. The method of claim 33, wherein the DL message comprises an operator binding update for a plurality of mobile network operators (MNOs), the operator binding update comprising the updated PKnw' for a wireless network of at least one of the MNOs.

35. The method of claim 34, wherein the network-based server comprises a third-party server maintained by an entity external to the MNO.

36. The method of claim 33, wherein the DL message comprises an over-the-air OTA update from a configuration server of an MNO, the DL message being provided to an embedded Universal Integrated Circuit Card (eUICC) or a physical Subscriber Identity Module (SIM) card of the UE.

37. The method according to claim 26, wherein the first UL message further comprises a key identifier ID, wherein the key ID indicates to the cellular wireless network entity which network public key PKnw the UE uses to derive the encryption key K for encrypting the SUCI. AES .

38. The method of claim 37, wherein the key ID comprises PKnw, a hash of PKnw, or a count value.

39. The method of claim 26, wherein the cellular wireless network entity comprises an evolved NodeB (eNodeB) or a next generation NodeB (gNB).

40. The method of claim 26, wherein: The SUPI comprises an International Mobile Subscriber Identity (IMSI); and The SUCI includes an encrypted version of the Mobile Subscriber Identification Number (MSIN) of the IMSI.

41. A method for protecting the privacy of a user identity included in a user equipment (UE), the method comprising: Initiating an attach procedure with a cellular wireless network entity; Sending a first uplink (UL) message to the cellular wireless network entity, wherein the first UL message includes a hidden user identifier (SUCI) generated by encrypting a user permanent identifier (SUPI); receiving an authentication failure indication from the cellular wireless network entity; Sending a fallback SUCI to the cellular wireless network entity FB The second UL message; When receiving an authentication success indication from the cellular wireless network entity in response to the second UL message, establishing a secure connection with the cellular wireless network entity; as well as when a second authentication failure indication is received from the cellular wireless network entity in response to the second UL message, terminating the attach procedure with the cellular wireless network entity, wherein the symmetric fallback encryption key K configured to the UE by a network entity of the cellular wireless network is at least partially based on FB or asymmetric fallback public key PK FB Encrypting the SUPI to generate the SUCI FB .

42. The method of claim 41, wherein: The SUCI is encrypted with an encryption key, wherein the encryption key is derived from a network public key PKnw provided by the cellular wireless network and a temporary UE secret key eSKue generated by the UE; The authentication failure indication includes using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB Signed updated network public key PKnw'; and The SUCI FB It is further encrypted using the updated network public key PKnw'.

43. The method of claim 41, wherein the method performed by the UE further comprises: After establishing the secure connection with the cellular wireless network entity, the UE: receiving a downlink DL message from a network-based server, the DL message including an updated network public key PKnw'; discarding the SUCI from a storage medium of the UE; The new encryption key K is derived based on the updated network public key PKnw' and the newly generated temporary UE secret key eSKue' AES '; Based on the SUPI and the new encryption key K AES 'to generate new SUCI'; as well as storing the new SUCI′ in the storage medium of the UE.

44. The method of claim 43, wherein the DL message comprises an operator binding update for a plurality of mobile network operators (MNOs), the operator binding update comprising the updated PKnw' for a wireless network of at least one of the MNOs.

45. The method of claim 41, wherein the first UL message further comprises a key identifier ID, wherein the key ID indicates to the cellular wireless network entity which network public key PKnw the UE uses to derive the encryption key K for encrypting the SUCI. AES .

46. ​​A method for protecting the privacy of a user identity included in a user equipment (UE), the method comprising: receiving a first uplink (UL) message from the UE, the first UL message including a user hidden identifier (SUCI) generated by encrypting a user permanent identifier (SUPI) based on a network public key (PKnw) and an identifier of PKnw; determining an authentication error of the UE based on expiration of a PKnw used by the UE; In response to the first UL message, a first downlink DL message is sent to the UE, wherein the first DL message includes an authentication failure indication and a fallback SUCI, that is, a SUCI. FB Requests; receiving, from the UE, the SUCI FB The second UL message; determining successful authentication based at least in part on the second UL message; In response to the second UL message, sending a second DL message including an authentication success indication from a cellular wireless network entity to the UE; and establishing a secure connection with the UE after successful authentication; The UE uses a symmetric fallback encryption key K configured to the UE by a network entity of the cellular wireless network at least in part. FB or asymmetric fallback public key PK FB Encrypting the SUPI to generate the SUCI FB .

47. The method of claim 46, wherein: The SUCI is encrypted by the UE using an encryption key, wherein the encryption key is derived from a network public key PKnw previously provided to the UE by the cellular wireless network and a temporary UE secret key eSKue generated by the UE; The authentication failure indication includes using the symmetric fallback encryption key K FB or the asymmetric fallback public key PK FB Signed updated network public key PKnw'; and The SUCI FB It is further encrypted using the updated network public key PKnw'.

48. The method according to claim 46, wherein the identifier of PKnw included in the first UL message is a key identifier ID, wherein the key ID indicates to the cellular wireless network entity which network public key PKnw the UE uses to derive the encryption key K for encrypting the SUCI. AES .

49. The method of claim 48, wherein the key ID comprises PKnw, a hash of PKnw, or a count value.

50. The method of claim 46, wherein the authentication failure indication comprises a request for the UE to use the SUCI FB Retry authentication message.

51. A non-transitory computer readable storage medium having computer readable code stored thereon, which, when executed by a processor, causes a device to implement the operations of the method according to any one of claims 26 to 50.

52. A computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 26 to 50.

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