Secure Mobile Authentication with Ephemeral IMSI Ranges
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Solution Overview
Problem
Current authentication protocols in mobile devices and servers face challenges in securing data exchanges due to data size encoding constraints, particularly in protocols like Easy Connect, which restrict the use of traditional ciphering methods, necessitating a new approach that ensures security, privacy, integrity, and authenticity while accommodating limited and dissymmetric payload sizes.
Innovation Solution
A method utilizing a shared range of ephemeral IMSIs and a group master key for initialization, followed by individual keys derived from a mobile device's credential container identifier, enables secure communication by encrypting only necessary parameters and minimizing data transmission, employing symmetric cryptography to address payload size constraints and ensure data privacy, integrity, and authenticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ciphering methods are used to secure data exchanges, then security and data privacy are improved, but data size constraints in protocols like Easy Connect cannot be satisfied
Solution Approach 1:
The authentication process is segmented into two distinct phases: initialization phase using shared group credentials (IMSI range and group master key) for efficient authentication, and secured communication phase using individually derived keys for encrypted data exchange. This segmentation allows the system to satisfy both security requirements and payload size constraints by using appropriate authentication mechanisms for each phase.
Solution Approach 2:
The system performs preliminary authentication during the initialization phase using compact credentials (IMSI range and group master key) before establishing the secured communication phase. This preliminary action enables the server to verify device authenticity with minimal payload, then derive individual keys for subsequent encrypted communications, effectively resolving the contradiction between security and payload size.
2Reliability
If individual keys are derived and used for each device, then data privacy and authenticity are improved, but the complexity of key management increases
Solution Approach 1:
The system transitions from traditional single-dimension key management to a two-dimensional approach: group-level credentials (IMSI range and group master key) for initial authentication, and device-level individually derived keys for secured communication. This dimensional change enables efficient key management by separating authentication functions from encryption functions, reducing overall system complexity while maintaining strong security.
3Adaptability or versatility
If payload size is minimized to meet protocol constraints, then protocol compatibility is improved, but the amount of encrypted data transmitted is reduced
Solution Approach 1:
The invention extracts and separates the authentication function from the data encryption function. During the initialization phase, authentication is performed using minimal payload (IMSI range and group master key). During the secured communication phase, individually derived keys are used to encrypt only the essential data parameters. This extraction approach ensures protocol compatibility with minimal payload while maintaining adequate encryption coverage for security-critical information.
Data Source
Figure 1~2A
Figure 2B~3
AI summary
The present invention relates to a method to securely attach a mobile device (MD) having a credential container (CC) to a server (SV) while using a protocol having data size encoding constraints which prevents from using traditional ciphering, said method comprising an initialization phase using a same range of ephemeral IMSIs (RG1(IMSI)) stored in a batch of credential containers (CC) of mobile devices (MD) and an associated group master key (MK11) shared by the server (SV) and the batch of credential containers (CC) of mobile devices (MD) having the same range of ephemeral IMSIs (RG1(IMSI)) to initiate the secured session further using a server random value (Rnd), said initialization phase using limited payload in a first mobile device (MD) to server (SV) message (ATTR(rIMSI)_1) to send a randomly chosen rIMSI among the range of IMSIs (RG1(IMSI)) to enable the server (SV) to generate keys to initiate a secured communication phase then using individual keys (SK12c, SK12i) stored in the credential container (CC) of the mobile device (MD) and retrieved by the server (SV) with an identifier of the credential container (CCId) also sent using limited payload in a mobile device (MD) to server (SV) message (AUTF(rIMSI, AUTS)_3) and with an individualization master key (MK12) owned by the server (SV).