What is SIDF (Subscription Identifier De Concealing Function)

SIDF (Subscription Identifier De-concealing Function) Explained Technically

Within the realm of 5th Generation (5G) mobile networks, the Subscription Identifier De-concealing Function (SIDF) plays a critical role in ensuring user privacy and security while maintaining efficient network operation. Here's a detailed breakdown of its functionality:

Background: Privacy Concerns in 5G Networks

• Unlike 4G networks where user equipment (UE) transmits its permanent identifier (IMSI) during initial access, 5G prioritizes user privacy.
• The permanent identifier, IMSI, is replaced with a more privacy-preserving identifier called the Subscription Permanent Identifier (SUPI).
• However, the SUPI cannot be directly transmitted over the air interface due to security concerns.

Function of SIDF:

• The SIDF acts as a critical component within the Unified Data Management (UDM) function of the 5G core network.
• It's responsible for decrypting a temporary identifier called the Subscription Concealed Identifier (SUCI) to reveal the corresponding SUPI.

Process Flow:

1. SUCI Transmission: During initial network access or service requests, the UE transmits a SUCI instead of the SUPI over the air interface.
   • The SUCI is generated by the UE using a specific protection scheme to conceal the SUPI.
2. SUCI Reception and Decryption: The SUCI is received by the network and forwarded to the UDM.
   • The SIDF within the UDM utilizes the appropriate decryption algorithm based on the protection scheme used to generate the SUCI.
3. SUPI Retrieval: By decrypting the SUCI, the SIDF retrieves the original SUPI associated with the UE.
4. Network Processing: The UDM can then use the retrieved SUPI to access relevant user subscription information and perform necessary network operations (e.g., authentication, authorization, service provisioning) for the UE.

Benefits of SIDF:

• Enhanced User Privacy: By concealing the SUPI during air interface communication, SIDF helps safeguard user privacy and prevents unauthorized access to a user's permanent identifier.
• Improved Security: The use of temporary identifiers like SUCI in conjunction with SIDF reduces the risk of exposure of permanent identifiers in case of network breaches.
• Efficient Network Operation: Despite the additional decryption step, SIDF enables the network to efficiently identify and manage UEs by allowing access to relevant subscription information based on the revealed SUPI.

Technical Considerations:

• The specific decryption algorithms employed by the SIDF depend on the chosen SUCI protection scheme. Common schemes include Extensible Authentication Protocol (EAP) AKA and public key cryptography-based approaches.
• The security and efficiency of the SIDF operation rely heavily on robust key management practices within the network.

Conclusion:

The SIDF plays a vital role in balancing user privacy and security with efficient network operation in 5G mobile networks. By enabling the use of temporary identifiers and facilitating their decryption for authorized access, SIDF contributes to a secure and privacy-conscious communication environment for 5G users. As 5G technology continues to evolve, the design and implementation of SIDF are expected to remain crucial aspects of user privacy protection within mobile communication networks.