Apparatus, method, and computer program for privacy protection of subscription identifiers

Abstract

There is provided an apparatus comprising components for receiving an indication of a length of at least a portion of a subscription identifier, determining the subscription identifier based on the received indication, encrypting the determined subscription identifier, and providing the encrypted subscription identifier to a network.

Description

Technical Field

[0001] The present application relates to a method, apparatus, system, and computer program, and in particular but not limited to privacy protection of NAI identifiers of distinguishable length. Background Art

[0002] A communication system may be viewed as a facility that enables communication sessions between two or more entities (such as user terminals, base stations, and / or other nodes) by providing carrier waves between the various entities involved in the communication path. For example, a communication system may be provided by means of a communication network and one or more compatible communication devices. A communication session may include, for example, communications for carrying data such as voice, video, electronic mail (email), text messaging, multimedia, and / or content data. Non-limiting examples of the services provided include two-way or multi-way calls, data communications, or multimedia services, and access to data network systems (such as the Internet).

[0003] In a wireless communication system, at least part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMNs), satellite-based communication systems, and different wireless local area networks, such as wireless local area networks (WLANs). Some wireless systems can be divided into cells and are therefore often referred to as cellular systems.

[0004] A user may access a communication system by means of an appropriate communication device or terminal. The user's communication device may be referred to as a user equipment (UE) or user device. The communication device is equipped with appropriate signal receiving and sending means for enabling communication, such as enabling access to a communication network or direct communication with other users. The communication device may access a carrier provided by a station (e.g., a base station of a cell) and send and / or receive communications on the carrier.

[0005] A communication system and associated equipment typically operate according to a given standard or specification, which specifies what the various entities associated with the system are allowed to do and how it should be achieved. The communication protocols and / or parameters used for the connection are also typically defined. An example of a communication system is UTRAN (3G radio). Other examples of communication systems are the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology and the so-called 5G or New Radio (NR) networks. NR is being standardized by the Third Generation Partnership Project (3GPP). Summary of the invention

[0006] In a first aspect, an apparatus is provided that includes means for receiving an indication of a length of at least a portion of a subscription identifier, determining a subscription identifier based on the received indication, encrypting the determined subscription identifier, and providing the encrypted subscription identifier to a network.

[0007] The apparatus may include means for extending at least a portion of the subscription identifier to the length.

[0008] The apparatus may include means for truncating at least a portion of the subscription identifier to the length.

[0009] The length can be fixed or variable.

[0010] The length can be a maximum length.

[0011] The apparatus may include means for receiving the indication from a home network.

[0012] The apparatus may include means for receiving the indication from an operator.

[0013] The subscription identifier may include a network access identifier.

[0014] At least a portion of the subscription identifier may include a username.

[0015] The apparatus may comprise a Universal Subscription Identifier Module, USIM, and means for providing an indication of a subscription identifier to a terminal comprising the USIM.

[0016] In a second aspect, an apparatus is provided, the apparatus comprising means for providing an indication of a length of at least part of a subscription identifier to a Universal Subscription Identifier Module (USIM), and receiving an encrypted subscription identifier from the USIM, wherein the subscription identifier is determined at a user equipment based on the provided indication.

[0017] At least part of the subscription identifier may be extended to this length.

[0018] The apparatus may include means for decrypting the encrypted subscription identifier and using at least a portion of the subscription identifier other than the extension portion.

[0019] At least part of the subscription identifier may be truncated to this length.

[0020] The length can be fixed or variable.

[0021] The length can be a maximum length.

[0022] The apparatus may include means for providing the indication from a home network.

[0023] The apparatus may comprise means for providing the indication from an operator.

[0024] The subscription identifier may include a network access identifier.

[0025] At least a portion of the subscription identifier may include a username.

[0026] In a third aspect, a method is provided, the method comprising receiving an indication of a length of at least a portion of a subscription identifier, determining a subscription identifier based on the received indication, encrypting the determined subscription identifier, and providing the encrypted subscription identifier to a network.

[0027] The method may include extending at least part of the subscription identifier to the length.

[0028] The method may include truncating at least part of the subscription identifier to the length.

[0029] The length can be fixed or variable.

[0030] The length can be a maximum length.

[0031] The method may include receiving the indication from a home network.

[0032] The method may include receiving the indication from an operator.

[0033] The subscription identifier may include a network access identifier.

[0034] At least a portion of the subscription identifier may include a username.

[0035] The method may comprise providing an indication of the subscription identifier to a terminal comprising a USIM.

[0036] In a fourth aspect, a method is provided, the method comprising providing an indication of a length of at least part of a subscription identifier to a universal subscription identifier module, USIM, and receiving an encrypted subscription identifier from the USIM, wherein the subscription identifier is determined at a user equipment based on the provided indication.

[0037] At least part of the subscription identifier may be extended to this length.

[0038] The method may include decrypting the encrypted subscription identifier and using at least a portion of the subscription identifier other than the extension portion.

[0039] At least part of the subscription identifier may be truncated to this length.

[0040] The length can be fixed or variable.

[0041] The length can be a maximum length.

[0042] The method may include providing the indication from the home network.

[0043] The method may include providing the indication from an operator.

[0044] The subscription identifier may include a network access identifier.

[0045] At least a portion of the subscription identifier may include a username.

[0046] In a fifth aspect, a device is provided, comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, causes the device to at least: receive an indication of a length of at least a portion of a subscription identifier, determine a subscription identifier based on the received indication, encrypt the determined subscription identifier, and provide the encrypted subscription identifier to a network.

[0047] The apparatus may be caused to extend at least part of the subscription identifier to the length.

[0048] The apparatus may be caused to truncate at least part of the subscription identifier to the length.

[0049] The length can be fixed or variable.

[0050] The length can be a maximum length.

[0051] The apparatus may be caused to receive the indication from a home network.

[0052] The apparatus may be caused to: receive the indication from an operator.

[0053] The subscription identifier may include a network access identifier.

[0054] At least a portion of the subscription identifier may include a username.

[0055] The apparatus may comprise a Universal Subscription Identifier Module, USIM, and be caused to provide an indication of the subscription identifier to a terminal comprising the USIM.

[0056] In a sixth aspect, a device is provided, comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, causes the device to at least: provide an indication of the length of at least part of a subscription identifier to a universal subscription identifier module USIM, and receive an encrypted subscription identifier from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

[0057] At least part of the subscription identifier may be extended to this length.

[0058] The apparatus may be caused to decrypt the encrypted subscription identifier and use at least a portion of the subscription identifier other than the extension portion.

[0059] At least part of the subscription identifier may be truncated to this length.

[0060] The length can be fixed or variable.

[0061] The length can be a maximum length.

[0062] The apparatus may be caused to provide the indication from a home network.

[0063] The apparatus may be caused to provide the indication from an operator.

[0064] The subscription identifier may include a network access identifier.

[0065] At least a portion of the subscription identifier may include a username.

[0066] In a seventh aspect, a computer-readable medium is provided, the medium comprising program instructions for causing an apparatus to at least perform the following: receive an indication of a length of at least a portion of a subscription identifier, determine a subscription identifier based on the received indication, encrypt the determined subscription identifier, and provide the encrypted subscription identifier to a network.

[0067] The apparatus may be caused to perform: extending at least a portion of the subscription identifier to the length.

[0068] The apparatus may be caused to perform: truncating at least a portion of the subscription identifier to the length.

[0069] The length can be fixed or variable.

[0070] The length can be a maximum length.

[0071] The apparatus may be caused to perform: receiving the indication from a home network.

[0072] The apparatus may be caused to perform: receiving the instruction from an operator.

[0073] The subscription identifier may include a network access identifier.

[0074] At least a portion of the subscription identifier may include a username.

[0075] The apparatus may comprise a universal subscription identifier module, USIM, and be caused to perform the instructing of providing a subscription identifier to a terminal comprising the USIM.

[0076] In an eighth aspect, a computer-readable medium is provided, comprising program instructions for causing an apparatus to at least perform the following: provide an indication of the length of at least part of a subscription identifier to a universal subscription identifier module USIM, and receive an encrypted subscription identifier from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

[0077] At least part of the subscription identifier may be extended to this length.

[0078] The apparatus may be caused to perform: decrypting the encrypted subscription identifier and using at least a portion of the subscription identifier other than the extension portion.

[0079] At least part of the subscription identifier may be truncated to this length.

[0080] The length can be fixed or variable.

[0081] The length can be a maximum length.

[0082] The apparatus may be caused to perform: providing the indication from a home network.

[0083] The apparatus may be caused to perform: providing the indication from an operator.

[0084] The subscription identifier may include a network access identifier.

[0085] At least a portion of the subscription identifier may include a username.

[0086] In a ninth aspect, a non-transitory computer-readable medium is provided, the non-transitory computer-readable medium comprising program instructions for causing an apparatus to at least execute the method according to the third aspect or the fourth aspect.

[0087] In the above, many different embodiments have been described. It should be understood that other embodiments can be provided by combining any two or more of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0089] Figure 1 A schematic diagram of an example 5GS communication system is shown;

[0090] Figure 2 A schematic diagram of an example mobile communication device is shown;

[0091] Figure 3 A schematic diagram of an example control device is shown;

[0092] Figure 4A block diagram illustrating an example encryption of a SUPI for generating a SUCI;

[0093] Figure 5 A block diagram of 3GPP SUPI_NAI and 3GPP SUCI_NAI is shown;

[0094] Figure 6 shows a distribution graph of identifier lengths;

[0095] Figure 7 A flow chart showing a method according to an example embodiment is shown;

[0096] Figure 8 A flow chart showing a method according to an example embodiment is shown;

[0097] Fig. 9 A block diagram illustrating a SUPI_NAI and a SUCI_NAI according to an example embodiment; and

[0098] Fig.10 A signaling flow according to an example embodiment is shown. DETAILED DESCRIPTION

[0099] Before explaining the examples in detail, refer to Figures 1 to 3 Certain general principles of wireless communication systems and mobile communication devices are briefly explained to aid understanding of the technology behind the described examples.

[0100] An example of a suitable communication system is the 5G system (5GS). The network architecture in 5GS may be similar to that of Advanced LTE. The base stations of the NR system may be referred to as Next Generation Node Bs (gNBs). Changes in the network architecture may depend on the need to support various radio technologies and more refined QoS support, as well as some on-demand requirements, such as QoS levels for supporting user-perspective QoE. In addition, network-aware services and applications, as well as service- and application-aware networks may bring changes to the architecture. These are related to information-centric network (ICN) and user-centric content delivery network (UC-CDN) approaches. NR may use multiple-input multiple-output (MIMO) antennas, more base stations or nodes than LTE (the so-called small cell concept), including macro sites that operate in cooperation with smaller base stations, and may also employ various radio technologies to obtain better coverage and enhanced data rates.

[0101] 5G networks can utilize network function virtualization (NFV), which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that can be operationally connected or linked together to provide services. Virtualized network functions (VNFs) can include: one or more virtual machines that run computer program code using standard or general-purpose servers instead of custom hardware. Cloud computing or data storage can also be utilized. In radio communications, this can mean that node operations are performed at least in part in a server, host, or node that is operably coupled to a remote radio head. Node operations can also be distributed among multiple servers, nodes, or hosts. It should also be understood that the distribution of work between core network operations and base station operations may be different from LTE, or even non-existent.

[0102] Figure 1 A schematic diagram of a 5G system (5GS) 100 is shown. The 5GS may include a user equipment (UE) 102 (which may also be referred to as a communication device or terminal), a 5G radio access network (5GRAN) 104, a 5G core network (5GCN) 106, one or more application functions (AFs) 108, and one or more data networks (DNs) 110.

[0103] An example 5G core network (CN) includes functional entities. The 5GCN 106 may include: one or more access and mobility management functions (AMFs) 112, one or more session management functions (SMFs) 114, an authentication server function (AUSF) 116, a unified data management (UDM) 118, one or more user plane functions (UPFs) 120, a unified data repository (UDR) 122, and / or a network exposure function (NEF) 124. The UPF is controlled by the SMF (session management function), which receives policies from the PCF (policy control function).

[0104] The CN is connected to the terminal device via a radio access network (RAN). The 5G RAN may include: one or more gNodeB distributed unit functions connected to one or more gNodeB (GNB) centralized unit functions. The RAN may include one or more access nodes.

[0105] The UPF (User Plane Function) whose role is called PSA (Protocol Data Unit (PDU) Session Anchor) can be responsible for forwarding frames to and from the Data Network (DN) and establishing tunnels over 5G towards (multiple) UEs that exchange services with the DN.

[0106] Now refer to Figure 2 describing in more detail possible mobile communication devices, Figure 2A schematic partial cutaway view of a communication device 200 is shown. Such a communication device is generally referred to as a user equipment (UE) or terminal. Suitable mobile communication devices can be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) or mobile device, such as a mobile phone or so-called "smart phone", a computer equipped with a wireless interface card or other wireless interface facilities (e.g., a USB dongle), a personal data assistant (PDA) or a tablet computer equipped with a wireless communication function, an IP voice (VoIP) phone, a portable computer, a desktop computer, an image capture terminal device (such as a digital camera), a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), an intelligent device, a wireless customer premises equipment (CPE), or any combination of these devices, etc. For example, a mobile communication device can provide communication for carrying data such as voice, email (email), text messages, multimedia, etc. Therefore, a user can be supplied and provided with a variety of services via his communication device. Non-limiting examples of these services include two-way or multi-way calls, data communications or multimedia services, or simply access to a data communications network system such as the Internet. Broadcast or multicast data may also be provided to the user. Non-limiting examples of content include: downloads, television and radio programs, videos, advertisements, various alerts, and other information.

[0107] The mobile device is typically equipped with at least one data processing entity 201, at least one memory 202, and other possible components 203 for software and hardware-assisted execution of the tasks it is designed to perform, including controlling access to and communication with access systems and other communication devices. Data processing, storage, and other related control devices can be provided on appropriate circuit boards and / or in chipsets. This feature is represented by reference numeral 204. The user can control the operation of the mobile device with the help of a suitable user interface, such as a lower keyboard 205, voice commands, a touch-sensitive screen or touchpad, a combination thereof, etc. A display 208, a speaker, and a microphone can also be provided. In addition, the mobile communication device may include appropriate connectors (wired or wireless) to other devices and / or for connecting external accessories (e.g., hands-free devices).

[0108] The mobile device 200 may receive signals over the air or radio interface 207 via suitable means for receiving, and may transmit signals via suitable means for transmitting radio signals. Figure 2 In the mobile device, the transceiver arrangement is schematically represented by block 206. The transceiver arrangement 206 may be provided, for example, by means of a radio component and an associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0109] Figure 3 An example of a control device 300 for a communication system is shown, for example, to be coupled to and / or used to control a station of an access system, such as a RAN node, such as a base station, eNB or gNB, a relay node, or a core network node, such as a mobility management entity (MME) or an S-GW or P-GW, or a core network function, such as an AMF / SMF, or a server or a host. The method can be implemented in a single control device or across more than one control device. The control device can be integrated with a node or module of the core network or RAN or located outside it. In some embodiments, the base station includes a separate control device unit or module. In other embodiments, the control device can be another network element, such as a radio network controller or a spectrum controller. In some embodiments, each base station can have such a control device, and a control device arranged in a radio network controller. The control device 300 can be arranged to provide control of communications in a service area of ​​the system. The control device 300 includes: at least one memory 301, at least one data processing unit 302, 303, and an input / output interface 304. Via the interface, the control device can be coupled to a receiver and a transmitter of the base station. The receiver and / or the transmitter may be implemented as a radio front end or a remote radio head.

[0110] So-called International Mobile Subscriber Identity (IMSI) catchers are designed to attack the anonymity of the subscriber, thereby tracking and monitoring the associated UE. To protect against IMSI catchers, the 5G standard introduces encryption of the Subscription Permanent Identifier (SUPI) into the Subscription Hidden Identifier (SUCI) using the home network’s public key.

[0111] A 5G globally unique SUPI is assigned to each subscriber. SUCI is a privacy-preserving identifier that contains a hidden SUPI.

[0112] The Elliptic Curve Integrated Encryption Scheme (ECIES) is used to encrypt SUCI into SUPI, such as Figure 4 as shown in .

[0113] ECIES is a hybrid scheme where key exchange is based on asymmetric cryptography, and key derivation and encryption are based on symmetric cryptography. ECIES is a probabilistic encryption scheme where the same plaintext encrypted multiple times produces completely different ciphertexts that cannot be linked to each other or to the plaintext. 3GPP has standardized three protection schemes: Null Scheme, Profile A, and Profile B. The "Null Scheme" does not perform any actual encryption, but produces the same output as the input. Profiles A and B use Curve25519 or secp256r1, as well as AES-128-CTR and HMAC-SHA-256.

[0114] The SUPI type may be an International Mobile Subscriber Identity (IMSI) or a Network Specific Identifier (NSI).

[0115] SUCI includes SUPI type, home network identifier, other parameters, and hidden identifier. Only the hidden identifier part is encrypted by SUCI.

[0116] When the SUPI is of IMSI type, the Home Network Identifier consists of a 3-digit Mobile Country Code (MCC) and a 2-3-digit Mobile Network Code (MNC), and the Hidden Identifier contains an encrypted 9-10-digit Mobile Subscription Identification Number (MSIN).

[0117] As mentioned earlier, the existing 5G standard allows the use of a network specific identifier (NSI) as a SUPI.

[0118] The NSI may take the form of a Network Access Identifier (NAI) defined in the 3GPP standard.

[0119] When the type of SUPI is NSI, the Home Network Identifier consists of a variable-length string called a domain, and the Hidden Identifier contains a variable-length encrypted string called a username.

[0120] In other words, the NAI of the SUPI should be in the form of username@realm, which may have a variable length username, as specified in the 3GPP standard.

[0121] Figure 5 3GPP SUPI_NAI and SUCI_NAI specified in the 3GPP standard are shown. The SUPI containing the network specific identifier takes the form of a network access identifier (NAI). The NAI of the SUPI has the format of username@realm. In the SNPN scenario, the domain part of the NAI includes the MCC, MNC, and the NID of the SNPN. For the NAI of the SUCI, the username is encrypted.

[0122] Existing mechanisms for computing SUCI cannot provide complete indistinguishability of SUCI when corresponding SUPIs have different lengths.

[0123] For SUCI, Figure 4As shown in , the symmetric encryption scheme used is AES-128 in "Counter (CTR) mode" (AES-128-CTR). CTR mode is a typical block cipher operation mode using a block cipher algorithm. In this CTR mode, the length of the plaintext and the corresponding ciphertext are the same (128 bits for AES-128-CTR). Moreover, in the symmetric key setting, security concepts such as true or random, left or right, or semantic security are defined in the context of the same plaintext length. Therefore, according to these concepts, the security of AES-128 in CTR mode is meaningful only when the plaintexts of interest are of similar length.

[0124] The network may have the username portion of the NAI created from a real-world name, as early and current usage of such identifiers (eg, in ISIM (IP Multimedia Services Identity Module)) are based on real-world names.

[0125] The researchers analyzed name length data for the whole of Sweden (10 million people) and four regions (Sweden, China, India, and the United States) within an internal company and found that the length distribution has a tail. SUCIs with lengths far from the mean (to the left or to the right) have lower anonymity and, in the worst case, can be completely distinguished. In other words, for long or short (far from the mean) length of the NAI used in the SUPI, the SUCI can be uniquely identified. This affects subscriber privacy and can be abused by IMSI catchers.

[0126] Currently using Figure 6 The sixth padding scheme, “Tail Aware Block Length” padding (taBlk-lmr), is shown in . The intuition behind this is that the tail of a typical distribution has the lowest frequencies (indicating lower anonymity) and benefits most from padding. The middle of the distribution typically has higher frequencies, and padding these frequencies only promotes message expansion without significantly increasing privacy. Therefore, taBlk-lmr padding is Figure 6 As shown in , the length below the left (l) is padded to l; the length between l and the middle (m) is not padded; the length above m is padded to the right (r). This selective padding may result in a reduction in the overall message expansion.

[0127] Figure 7 A flow chart of a method according to an example embodiment is shown. The method may be performed at a USIM. The USIM is associated with a Mobile Equipment (ME), in other words a User Equipment.

[0128] In S1 , the method comprises receiving an indication of a length of at least a portion of a subscription identifier.

[0129] In S2, the method comprises determining a subscription identifier based on the received indication.

[0130] In S3, the method includes encrypting the determined subscription identifier.

[0131] In S4, the method comprises providing the encrypted subscription identifier to the network.

[0132] Figure 8 A flow chart of a method according to an example embodiment is shown.The method may be performed at a network function (eg, UDM) of a home network (HN).

[0133] In T1 , the method comprises providing an indication of a length of at least a part of a subscription identifier to a Universal Subscription Identifier Module (USIM).

[0134] At T2, the method comprises receiving an encrypted subscription identifier from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

[0135] The subscription identifier may be a NAI. At least a portion of the subscription identifier may be a username of the NAI.

[0136] Determining the subscription identifier may include extending or truncating at least a portion of the subscription identifier to the length.

[0137] The length can be fixed or variable. The length can be a maximum length.

[0138] In other words, the USIM may be configured with a fixed or variable username length, resulting in a fixed SUCI size each time, or each iteration of generation may result in a different SUCI size for the same UE.

[0139] The method provides for adding an extension of a user name included in an NSI (in the form of an NAI) when the NAI length is shorter than the average length, or for truncating a user name in an NSI (in the form of an NAI) when the NAI length is longer than the average length.

[0140] The expansion or truncation scheme can be derived statistically and automatically, with or without any input from the operator.

[0141] This method can ensure that the length of the NSI, which is part of the SUPI and is used to generate the SUCI, is constant.

[0142] The extension of the username in the SUPI NAI may be configured in the USIM by the UDM or the operator.

[0143] The method may comprise receiving an indication of the length from an operator or home network (eg, from a function of the HN such as UDM).

[0144] The SUCI NAI generated for all users within the same operator may be of the same length as the encrypted text, since the SUCI generation takes into account the added extension of the plaintext.

[0145] The extension is configurable by the operator and is therefore operator specific, so the username is a constant length with that username extension.

[0146] The extended subscription identifier may be in the form of username!anonymity@realm. For example, the NAI of SUPI may have the form of username!extension@realm.

[0147] The content of the username extension is not configurable by the operator, but is filled in by the user using any "non-empty string" after the "!" in the username.

[0148] The method may include decrypting the encrypted subscription identifier and using at least a portion of the subscription identifier other than the extension portion.

[0149] In other words, during unhiding, UDM ignores the octet after the "!" in the username.

[0150] Each operator may have its own specific extension length. For example, the maximum length of the username extension for PLMN A is 200 octets. Although each user within the same PLMN A may have a different username and username length, the extension after the "!" in the username is used in the SUPI_NAI, so the maximum length of the username for each user in PLMN A is 200 octets.

[0151] Assume that PLMN B allows a maximum user name extension length of 253 octets. USIMs under this operator will have different user name sizes. Therefore, each user's user name is extended with "!" and each user has "any non-empty string" added to it.

[0152] Privacy protection of SUPI NAI or SUCI NAI can be achieved

[0153] Fig. 9 The NAI of a SUPI according to an example embodiment is shown. The SUPI_NAI includes an extension of the username for anonymity. The username with anonymity is encrypted to form the SUCI_NAI. The length of the SUCI_NAI is the same as the length of the SUPI_NAI.

[0154] Each user within the same operator has a predefined or configured maximum length for the username portion. The input length for the SUCI calculation becomes a constant with the total number of characters equal to the maximum length defined by the operator. This provides consistency between different users of the same operator.

[0155] Table 1 shows an encoding example when the SUPI type is a network specific identifier.

[0156]

[0157] Table 1

[0158] A Network Specific Identifier in NAI format is a NAI constructed as specified by the standard and encoded as a UTF-8 string. The Network Specific Identifier extension may or may not be set (the Username extension for anonymity is set to "Variable" or "Fixed"), which is optionally configurable by the operator. The Network Specific Identifier extension length (conditionally valid only if the extension is set to "Fixed") is the maximum octet allowed in a username, so additional octets may be added after the Network Specific Identifier.

[0159] If the operator has configured a fixed NAI for the UE, then each time a SUCI is generated using the NAI format, the bytes after the "!" must be filled with the contents of the username, e.g. the length of "username!extension_of_userid" is always the same as the maximum length configured by the operator. Regardless of the number of times the SUCI is generated, the size is the same each time for the same UE.

[0160] If the operator has configured a variable NAI for the UE, the bytes after the "!" must be filled with the contents of the username each time a SUCI in NAI format is generated, e.g. the length of "username!extension_of_userid" is variable each time. Regardless of the number of times the SUCI is generated, the size of the SUCI is different each time for the same UE. After unhiding, the operator will ignore the contents after the "!".

[0161] Assuming the network specific identifier is user17!extension_of_userid_for_anonymity@example.com, the routing indicator is 678, and the home network public key identifier is 27, the NAI format of SUCI takes the following form for the null scheme:

[0162] type1.rid678.schid0.useriduser17!extension_of_userid_for_anonymity@example.com

[0163] For anonymous SUCI, the following forms are adopted:

[0164] type1.rid678.schid0.useridanonymous!extension_of_userid_for_anonymity@example.com (where username corresponds to "anonymity"), or

[0165] type1.rid678.schid0.userid!extension_of_userid_for_anonymity@example.com (where username corresponds to the empty string)

[0166] For profile The protection scheme takes the following form:

[0167] type1.rid678.schid1.hnkey27.ecckey <ECC temporary public key>.cip <encrypted with extended user17>.mac <mac tag value>@example.com.

[0168] Fig.10 A signaling flow according to an example embodiment is shown.

[0169] In step 1, a successful primary authentication is performed using SUCI as IMSI format.

[0170] Step 2 and step 3 are two potential ways to update the configuration in the USIM.

[0171] In step 2, the Home Network (HN) uses existing UPU or SoR procedures to update the USIM with the NSI extension and the length to be used.

[0172] Alternatively or additionally, the operator updates and extends the information over the air (OTA) using the existing USIM as shown in step 3. This step can be performed even if the UE is in idle mode.

[0173] In step 4, the operator configures the SUPI NAI to a fixed maximum or specific length.

[0174] In step 5, a SUCI NAI is generated as described in the 3GPP standard. The SUPI_NAI includes an extension value after the user name.

[0175] In step 6, the ME sends a SUPI_NAI request and reads the EF file of the SUPI_NAI with the anonymity configured username from the USIM.

[0176] In step 7, the ME requests SUCI_NAI and the USIM shares the generated SUCI.

[0177] In step 8, the ME sends SUCI_NAI to the HN.

[0178] In step 9, after unhiding of SUCI_NAI, UDM retrieves SUPI_NAI as "username!anonymity@realm". UDM ignores the content after "!" and only considers the username part.

[0179] The following example data set corresponds to SUCI calculation for SUPI and ECIES profile A based on a network specific identifier in a UE.

[0180] SUPI is:

[0181] verylongusername1!extension_anonymity_username@3gpp.com

[0182] The ECIES scheme output is calculated in the UE as described in TS 33.501 clause C.3.2, using the following example data.

[0183] Home Network Private Key:

[0184] 'C53C22208B61860B06C62E5406A7B330C2B577AA555898151

[0185] 0D128247D38BD1D'

[0186] Home Network Public Key:

[0187] '5A8D38864820197C3394B92613B20B91633CBD897119273BF

[0188] 8e4A6f4EEC0A650'

[0189] Eph.Private key:

[0190] 'BE9EFF3E9F22A4B42A3D236E7A6C500B3F2E7E0C7449988BA800D664BF4FCD97'

[0191] Eph. Public key:

[0192] '977D8B2FDAA7B64AA700D04227D5B440630EA4EC50F9082

[0193] 273A26BB678C92222'

[0194] Eph. Shared Key:

[0195] '511C1DF473BB88317F923501F8BA944FD3B667D25699DCB5

[0196] 52DBCEF60BBDC56D'

[0197] Eph.Enc.Key:

[0198] 'FE77B87D87F40428EDD71BCA69D79059'

[0199] Plaintext block:

[0200] '766572796C6F6E67757365726E616D6531796C6F6E677573657

[0201] 26E501F8BA944FD3B667D25699D'

[0202] Ciphertext value:

[0203] '8E358A1582ADB15322C10E515141D2039Ae61af4ebdbd293ea

[0204] 4f942696b9e8156a7b3f6709a079'

[0205] Eph.mac Key:

[0206] 'D87B69F4FE8CD6B211264EA5E69F682F151A82252684CDB1

[0207] 5A047E6EF0595028'

[0208] MAC tag value:

[0209] '12E1D7783A97F1AC'

[0210] Solution output:

[0211] ecckey977D8B2FDAA7B64AA700D04227D5B440630EA4EC50F

[0212] 9082273A26BB678C92222.cip8E358A1582ADB15322C10E51514

[0213] 1D2039Ae61af4ebdbd293ea4f942696b9e8156a7b3f6709a079.mac1

[0214] 2E1D7783A97F1AC

[0215] An apparatus may include means for receiving an indication of a length of at least a portion of a subscription identifier, determining a subscription identifier based on the received indication, encrypting the determined subscription identifier, and providing the encrypted subscription identifier to a network.

[0216] Alternatively or additionally, an apparatus may comprise means for providing an indication of a length of at least part of a subscription identifier to a universal subscription identifier module, USIM; and receiving an encrypted subscription identifier from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

[0217] It should be understood that these devices may include or be coupled to other units or modules for transmission and / or reception, such as radio components or radio heads. Although these devices are described as one entity, different modules and memories may be implemented in one or more physical or logical entities.

[0218] It should be noted that although some embodiments have been described with respect to 5G networks, similar principles may also be applied to other networks and communication systems. Thus, although certain embodiments are described above by way of example with reference to certain example architectures of wireless networks, technologies and standards, the embodiments may be applied to any other suitable form of communication system other than that shown and described herein.

[0219] It is also noted herein that while the above describes exemplifying embodiments, there are numerous variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0220] In general, various embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device, but the disclosure is not limited thereto. Although various aspects of the disclosure may be shown and described as block diagrams, flow charts, or using some other graphical representation, it is well understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0221] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0222] (a) hardware circuit implementation only (such as implementation only in analog and / or digital circuitry) and

[0223] (b) a combination of hardware circuitry and software such as (where applicable):

[0224] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0225] (ii) hardware processor(s) (including digital signal processor(s)), software, and any portion of memory(s) with software, which work together to enable a device such as a mobile phone or server to perform various functions), and (c) hardware circuit(s) and / or processor(s), such as microprocessor(s) or portion(s) of microprocessor(s), which require software (e.g., firmware) to run, but where the software is not required to run, the software may be absent.

[0226] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also includes a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0227] Embodiments of the present disclosure may be implemented by computer software executable by a data processor of a mobile device, such as in a processor entity, or by hardware, or by a combination of software and hardware. Computer software or programs (also referred to as program products, including software routines, applets and / or macros) may be stored in any device-readable data storage medium, and they include program instructions for performing specific tasks. A computer program product may include one or more computer executable components that are configured to perform an embodiment when the program is running. One or more computer executable components may be at least one software code or a portion thereof.

[0228] Furthermore, in this regard, it should be noted that any block of the logic flow as shown in the figure may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, boxes and functions. The software may be stored on physical media implemented within a processor such as memory chips or memory blocks, magnetic media such as hard disks or floppy disks, and optical media such as DVDs and their data variants CDs. Physical media are non-transitory media.

[0229] The memory may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The data processor may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a gate-level circuit, and a processor based on a multi-core processor architecture, as non-limiting examples.

[0230] Embodiments of the present disclosure may be implemented in various components such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert logic-level designs into semiconductor circuit designs for etching and formation on semiconductor substrates.

[0231] The independent claims define the scope of protection sought by various embodiments of the present disclosure. Embodiments and features described in this specification that do not fall within the scope of the independent claims, if any, are to be construed as examples that aid in understanding the various embodiments of the present disclosure.

[0232] The foregoing description provides a complete and informative description of exemplary embodiments of the present disclosure by way of non-limiting examples. However, when read in conjunction with the accompanying drawings and the appended claims, various modifications and adjustments may be apparent to those skilled in the relevant art in view of the foregoing description. However, all of these and similar modifications of the teachings of the present disclosure will still fall within the scope of the present invention as defined in the appended claims. In fact, there are additional embodiments that may include a combination of one or more embodiments with any other embodiments previously discussed.

Claims

1. A device comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least: receiving an indication of a length of at least a portion of a subscription identifier; determining the subscription identifier based on the received indication; encrypting the determined subscription identifier; as well as The encrypted subscription identifier is provided to a network. 2 . The apparatus of claim 1 , wherein the apparatus is caused to extend the at least portion of the subscription identifier to the length.

3. The apparatus of claim 1, wherein the apparatus is caused to truncate the at least portion of the subscription identifier to the length.

4. The device according to any one of claims 1 to 3, wherein the length is fixed or variable.

5. The device according to any one of claims 1 to 4, wherein the length is a maximum length.

6. An apparatus according to any one of claims 1 to 5, wherein the apparatus is caused to receive the indication from a home network.

7. The apparatus according to any one of claims 1 to 6, wherein the apparatus is configured to receive the indication from an operator.

8. The apparatus of any one of claims 1 to 7, wherein the subscription identifier comprises a network access identifier.

9. The apparatus of claim 8, wherein the at least portion of the subscription identifier comprises a username.

10. An apparatus according to any one of claims 1 to 9, wherein the apparatus comprises a Universal Subscription Identifier Module (USIM) and is caused to provide an indication of the subscription identifier to a terminal comprising the USIM.

11. An apparatus comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least: providing an indication of the length of at least part of the subscription identifier to a universal subscription identifier module USIM; as well as An encrypted subscription identifier is received from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

12. The apparatus of claim 11, wherein the at least portion of the subscription identifier is extended to the length.

13. An apparatus according to claim 12, wherein the apparatus is caused to decrypt the encrypted subscription identifier and use the at least part of the subscription identifier other than the extension part.

14. The apparatus of claim 11, wherein the at least portion of the subscription identifier is truncated to the length.

15. The device according to any one of claims 11 to 14, wherein the length is fixed or variable.

16. The device according to any one of claims 11 to 15, wherein the length is a maximum length.

17. An apparatus according to any one of claims 11 to 16, wherein the apparatus is caused to provide the indication from a home network.

18. An apparatus according to any one of claims 11 to 17, wherein the apparatus is caused to provide the indication from an operator.

19. The apparatus of any one of claims 11 to 18, wherein the subscription identifier comprises a network access identifier.

20. The apparatus of claim 19, wherein the at least portion of the subscription identifier comprises a username.

21. A method comprising: receiving an indication of a length of at least a portion of a subscription identifier; determining the subscription identifier based on the received indication; encrypting the determined subscription identifier; as well as The encrypted subscription identifier is provided to a network.

22. A method comprising: providing an indication of the length of at least part of the subscription identifier to a universal subscription identifier module USIM; as well as An encrypted subscription identifier is received from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

23. An apparatus comprising components for: receiving an indication of a length of at least a portion of a subscription identifier; determining the subscription identifier based on the received indication; encrypting the determined subscription identifier; as well as The encrypted subscription identifier is provided to a network.

24. An apparatus comprising components for: providing an indication of the length of at least part of the subscription identifier to a universal subscription identifier module USIM; and An encrypted subscription identifier is received from the USIM, wherein the subscription identifier is determined at the user equipment based on the provided indication.

25. A computer-readable medium comprising program instructions for causing an apparatus to at least perform the following: receiving an indication of a length of at least a portion of a subscription identifier; determining the subscription identifier based on the received indication; encrypting the determined subscription identifier; as well as The encrypted subscription identifier is provided to a network.

26. A computer readable medium comprising program instructions for causing an apparatus to at least perform the following: providing an indication of the length of at least part of the subscription identifier to a universal subscription identifier module USIM; and An encrypted subscription identifier is received from the USIM, wherein the subscription identifier is determined at the USIM based on the provided indication.

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