Method for sending data to a user equipment cooperating with a secure element and corresponding server

Abstract

The present invention relates to a method for sending data to a user equipment (10) cooperating with a secure element, said method comprising: - exchanging information in a signaling message between the secure element and a server (11) acting as an AUSF / UDM to send a temporary IMSI to the secure element, and using procedures for steering of user equipment within a VPLMN during registration, as defined by 3GPP TS 33.501 V17.5.0 (2022-03) entitled "Security architecture and procedures for 5G systems (Release 17)", for sending the data from the server (11) to the secure element.

Description

[Technical Field]

[0001] The present invention relates to telecommunications in cellular networks, and more particularly to the transmission of data to a secure element, preferably a non-removable secure element such as an integrated UICC (iUICC) or an embedded UICC (eUICC). [Background technology]

[0002] The secure element may be embodied in different form factors, such as a smart card, a UICC, an embedded UICC, or an integrated UICC.

[0003] Traditional smart card form factors are generally physically removable (from the card reader), for example in the form of a SIM card.

[0004] An embedded UICC is a non-removable secure element soldered onto an electronic board configured within such a terminal.

[0005] An integrated UICC is a non-removable secure element that has the particularity of being combined within a system on a chip (SoC).

[0006] The present invention proposes an enhanced initial mobile connection in 5G networks, especially in 5G standalone networks.

[0007] From EP-3 358 867 A1 and EP-3 358 868 A1, which are incorporated herein by reference, a method for managing communication between a server and a user equipment is known, which method in particular relates to the establishment of a communication channel between a server and a user equipment that does not have full telecommunication credentials.

[0008] To securely connect to a telecommunications network, a user equipment needs to be provisioned with its complete telecommunications credentials (profile) including the IMSI / Ki pair, where IMSI is a unique identifier for the telecommunications subscription and Ki is a secret key uniquely allocated to the subscription by the mobile network operator.

[0009] The IMSI / Ki pair is typically stored in a tamper-resistant element (also called a secure element), which can be a SIM card, a Universal Integrated Circuit Card (UICC), an embedded secure element (e.g., eUICC), a software secure enclave in a system-on-chip (SOC) or an integrated secure element (i.e., iUICC).

[0010] A tamper-resistant element is considered secure because it can control access to the data it contains and authorize or not authorize the use of these data by other machines or entities. A tamper-resistant element may also provide computational services based on cryptographic components (also known as cryptographic processors). Generally, a tamper-resistant element has limited computational resources and limited memory.

[0011] Due to the manufacturing process, user equipment (and its tamper-resistant elements) may be issued without an IMSI / Ki pair.

[0012] There is a need to securely establish a communication session between such a user equipment and a server, which is intended to enable the user equipment to obtain, among other things, an IMSI / Ki pair.

[0013] The above mentioned patent application describes a solution to this problem.

[0014] More precisely, the first one (EP-3 358 867 A1) describes a method of communication between a server and a user equipment through a set of command / response pairs. The user equipment uses the IMSI field of the Attach Request frame, as specified by ETSI TS 124.008, to transmit one command of these pairs to the server. The server uses the Authentication Parameter RAND field or the Authentication Parameter AUTN field of the Authentication Request frame, as specified by ETSI TS 124.008, to transmit a response corresponding to the received command. In response to the Attach Request frame, the server sends an Authentication Request frame.

[0015] Figure 1 represents such a process completed by steps that enable attachment of a user equipment to a network of an MNO (Mobile Network Operator).

[0016] In this diagram, three entities are represented: a user equipment 10 working with a secure element, a server 11 acting as HLR / HSS, and an SM-DP+ 12 (Subscription Manager Data Preparation).

[0017] The workflow is as follows: In a first step (step #1), the user equipment (or more precisely the secure element) selects an ephemeral IMSI, called e-IMSI, configured within a range of e-IMSIs. The MCC / MNC (Mobile Country Code / Mobile Network Code) of the e-IMSI corresponds to the MCC / MNC of the server 11. The MSIN part of the e-IMSI is advantageously modulo the EID of the eUICC to avoid collisions between different devices that may use the same e-IMSI.

[0018] The EID (eUICC Identifier) ​​is included in a barcode printed on the box containing the user equipment and is scanned by the user equipment vendor. The EID, thanks to the e-IMSI, is sent in an AUTS message (Attach Request frame) to the ephemeral MNO (e-MNO) network 13. The e-MNO network 13 is typically a 3G, 4G, or 5G NSA network (NSA stands for non-standalone, a 4G network operating with a 5G radio part). The authentication algorithm can be, for example, Milenage. The e-MNO 13 network is connected to the server 11, which returns a temporary IMSI (t-IMSI), an oPC key (operator key), and a PLMN (Private Land Mobile Network) list in a RAND or AUTN message. The t-IMSI is chosen by the server 11 in view of the EID and business rules (and the location of the user equipment 10).

[0019] In a second step (step #2), the user equipment 10 uses the received t-IMSI to connect to the network of the temporary MNO, t-MNO 14, connected to the SM-DP+ 12. The SM-DP+ 12 then downloads the complete profile to the secure element of the user equipment 10.

[0020] In a third step (step #3), the user equipment 10 is able to connect to the network of an operational MNO 15 thanks to the profile downloaded during step #2.

[0021] In step 1, the eUICC attaches to the server 13 by means of the e-IMSI only for authentication purposes, i.e. to run the Milenage algorithm. Phases like location update, actual attachment to the server 11, data connection, possibility to send SMS, subscriptions at this stage do not exist.

[0022] The PLMN list transmitted during step 1 is also dependent on the location of the user equipment, and this list is defined depending on the roaming agreement for using the preferred MNO.

[0023] In step 2, the secure element performs an IMSI switch to replace the e-IMSI with the t-IMSI, and a Refresh is performed to use the t-IMSI instead of the e-IMSI. [Prior art documents] [Patent documents]

[0024] [Patent Document 1] European Patent Application Publication No. 3358867 [Patent Document 2] European Patent Application Publication No. 3358868 Summary of the Invention [Problem to be solved by the invention]

[0025] The problem with this solution is that within the 5G SA network (SA stands for Standalone Access) it is desirable to send more data to the eUICC during step 1, for example (non-exhaustive list):

[0026] - Enable 5G SUCI encryption: In 5G SA networks, only unencrypted SUCI (null scheme) can be used for the initial connection in step 1. However, some MNOs may refuse to use unencrypted SUCI. One objective of the present invention is to enable uploading data required for SUCI encryption (such as home network public key);

[0027] - Send Ki, which will be used for the initial connection. Currently, Ki is calculated by using a secret in the eUICC and only OPc is sent. Sending Ki together with the oPC removes the need to store this secret in the eUICC, improving the overall security of the solution.

[0028] - Sending an "activation code" to the eUICC that indicates to the SM-DP+ 12 where to download the profile. [Means for solving the problem]

[0029] This problem is solved by using a standard protocol to send these auxiliary data from the server 11 to the eUICC.

[0030] More precisely, the present invention proposes a method for sending data to a user equipment working with a secure element, the method comprising exchanging information in signaling messages between the secure element and a server acting as AUSF / UDM to send a temporary IMSI to the secure element, and for sending data from the server to the secure element, the method is in accordance with the "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)" (3 rdThe purpose is to use the procedures for steering user equipment within a VPLMN during registration as specified in 3GPP TS 33.501 V17.5.0 (2022-03) entitled "5G Generation Partnership Project, Technical Specification Group Services and System Aspects, Security architecture and procedures for 5G system (Release 17)."

[0031] Preferably, the data is: - Information that allows the 5G SUCI to be calculated, or - the Ki to be used for the initial connection, or - An "activation code" that tells SM-DP+ where to download the profile is.

[0032] The present invention also relates to a server acting as an AUSF / UDM, the server being configured to send a temporary IMSI to a user equipment cooperating with a secure element, the server also sending some data to the secure element and using the procedures for steering user equipment within a VPLMN during registration as specified by 3GPP TS 33.501 V17.5.0 (2022-03) entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)" to route data from the server to the secure element.

[0033] The invention will be better understood by reading the following description of a preferred method according to the invention in conjunction with the figures which show: [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a diagram of a state-of-the-art solution. [Figure 2] 1 is a diagram of a method according to the invention; [Figure 3] 6.14.2.1-1, a diagram representing a known procedure called "Procedure for steering a UE within a VPLMN during registration," as defined by 3GPP TS 33.501 V17.5.0 (2022-03), entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)." DETAILED DESCRIPTION OF THE INVENTION

[0035] Figure 1 is explained from a state-of-the-art perspective.

[0036] FIG. 2 represents a preferred solution according to the invention.

[0037] In Figure 2, the same entities are represented as in Figure 1. The difference here is that the e-MNO network is a 5G SA network.

[0038] The first exchange of step 20 is identical to step 1 of Figure 1 (allocation of a t-IMSI to the eUICC configured in the user equipment 10 by the server 11). More precisely, the eUICC attaches to the network 13 using the ephemeral IMSI. The client 10 and the server 11 exchange data thanks to the specific values ​​of RAND, AUTN and AUTS of the Milenage authentication algorithm. These steps are described in EP-3 358 867 A1 and EP-3 358 868 A1.

[0039] Here, the server 11 acts as AUSF / UDM since the protocol is operating in 5G (AUSF / UDM corresponds to HSS in 4G networks).

[0040] This corresponds to steps 1 and 2 in Figure 3, which depicts the procedure for steering a UE within a VPLMN during registration as specified by 3GPP TS 33.501 V17.5.0 (2022-03) entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)." More precisely, this corresponds to Figure 6.14.2.1-1 of this technical specification.

[0041] However, in step 20 of Figure 2, the server 11 encodes additional data to be sent to the eUICC.

[0042] This corresponds to steps 3 to 15 in Figure 3, in which the steering list is sent from the server 11 to the eUICC in a secured packet. However, within the scope of the present invention, instead of sending the steering list, the server 11 sends other data to the eUICC in this secured packet. These other data are, for example:

[0043] - Information that allows to calculate the 5G SUCI (such as a key for SUCI encryption, e.g., the home network key): Without the present invention, only the unencrypted SUCI (i.e., the SUPI) can be used for the initial connection. However, as already mentioned, some MNOs may refuse to use an unencrypted SUCI. According to the proposed solution, it is possible to upload the data necessary for SUCI encryption (such as the home network public key).

[0044] - Send Ki, which will be used for the initial connection. Currently, Ki is calculated by using a secret in the eUICC and only OPc is sent. Sending Ki together with the oPC removes the need to store this secret in the eUICC, improving the overall security of the solution.

[0045] - Send an "activation code" that tells the SM-DP+ 12 where to download the profile.

[0046] After sending these data to the eUICC, the eUICC is registered with the server 11 and the attachment is dropped.

[0047] Thus, the attachment procedure relies on the 3GPP standard attachment flow, but uses specific semantics to exchange specific data of limited size.

[0048] Steps 21 and 22 are identical to steps 2 and 3 in FIG.

[0049] The present invention takes advantage of the 5G attachment procedure defined in the aforementioned technical specification, which includes an optional Steering of Roaming (SoR) phase immediately after authentication, during which the home network AUSF / UDM can send a secured packet containing the PLMN list to the device, which the device then provides it transparently to the eUICC.

[0050] The invention therefore consists in exploiting the SoR procedure to send additional data: the server 11 acting as AUSF / UDM can send secured packets containing these data instead of the PLMN list to the eUICC client, which can interpret and process these specific data.

[0051] Figure 3 illustrates the "Procedure for steering a UE within a VPLMN during registration" as specified by 3GPP TS 33.501 V17.5.0 (2022-03), Figure 6.14.2.1-1, entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)," and shows the following elements:

[0052] 10 is a user equipment working with a secure element, 13 is a visited PLMN (VPLMN), and 11 is a server acting as an AUSF / UDM.

[0053] These elements constitute the state of the art and will not be described further.

[0054] The present invention also resides in a server 11 acting as an AUSF / UDM, the server being configured to send a temporary IMSI to a secure element cooperating with the user equipment, the server also sending some data to the secure element and using the procedures for steering user equipment within a VPLMN during registration as specified by 3GPP TS 33.501 V17.5.0 (2022-03) entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)" to send data from the server to the secure element.

[0055] As already mentioned, these data are: - Information that allows the 5G SUCI to be calculated, or - the Ki to be used for the initial connection, or - An "activation code" that tells SM-DP+ where to download the profile is.

Claims

1. A method for sending data to a user equipment (10) cooperating with a secure element, said method comprising: - exchanging information in signaling messages between said secure element and a server (11) acting as AUSF / UDM, which allows sending a temporary IMSI to said secure element, The method comprises using a procedure for steering of user equipment within a VPLMN during registration as specified in 3GPP TS 33.501 V17.5.0 (2022-03) entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)" to send the data from the server (11) to the secure element, wherein the data is sent instead of a steering list.

2. The data is - Information that allows the 5G SUCI to be calculated, or the Ki to be used for the initial connection, or - An "activation code" that tells SM-DP+ where to download the profile The method of claim 1, wherein

3. The method of claim 1 or 2, wherein the secure element is an eUICC.

4. A server (11) acting as an AUSF / UDM, the server being configured to send a temporary IMSI to a user equipment (10) cooperating with a secure element, the server (11) also sending some data to the secure element, and using the procedure for steering of user equipment within a VPLMN during registration as specified by 3GPP TS 33.501 V17.5.0 (2022-03), entitled "3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Security Architecture and Procedures for 5G Systems (Release 17)", to send the data from the server to the secure element, the server (11) sending the data instead of a steering list.

5. The data is - Information that allows the 5G SUCI to be calculated, or the Ki to be used for the initial connection, or - An "activation code" that tells SM-DP+ where to download the profile The server (11) according to claim 4,

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