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SUCI (Subscription Concealed Identifier)

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The Subscription Concealed Identifier (SUCI) is a concept within the 5G (Fifth Generation) mobile communication standard. It is used for concealing the identity of a subscriber in certain scenarios while allowing the network to identify and authenticate the subscriber for the purpose of providing services. The SUCI is employed in conjunction with the 5G AKA (Authentication and Key Agreement) procedure. Let's delve into the technical details of the SUCI:

1. Purpose:

  • The primary purpose of the SUCI is to conceal the permanent identity of a subscriber during the initial registration and authentication process.

2. Components:

  • The SUCI comprises the following components:
    1. Home Network Public Key (HNPK):
      • The HNPK is a public key associated with the home network.
      • It is used to encrypt and protect certain parts of the SUCI.
    2. PLMN Identity:
      • PLMN stands for Public Land Mobile Network, and the PLMN Identity represents the identity of the subscriber's home network.
    3. AMF Identifier (AMFID):
      • The AMF Identifier identifies the Authentication Management Field (AMF) entity in the 5G core network.
    4. SUPI (Subscription Permanent Identifier):
      • The SUPI is the permanent identity of the subscriber, typically an International Mobile Subscriber Identity (IMSI).

3. Generation Process:

  • The SUCI is generated during the registration process when the subscriber initiates communication with the 5G network.
  • The Home Network generates the SUCI based on the subscriber's permanent identity (SUPI), PLMN Identity, and AMF Identifier.

4. Protection Mechanism:

  • The SUCI is protected to ensure the confidentiality and integrity of the concealed identity. This is achieved through cryptographic operations.
  • The HNPK is used to encrypt certain parts of the SUCI, making it difficult for eavesdroppers to decipher the subscriber's identity during transmission.

5. Use Cases:

  • Initial Registration:
    • During the initial registration of a subscriber with the 5G network, the SUCI is used to conceal the subscriber's permanent identity.
  • Authentication:
    • The SUCI is employed in the authentication process to allow the network to verify the subscriber's identity while keeping the SUPI concealed.
  • Handovers and Mobility:
    • SUCI may also be used during handovers and mobility procedures to maintain subscriber identity concealment.

6. Enhancements Over Previous Generations:

  • Compared to previous mobile communication generations, 5G introduces improvements in identity concealment through the SUCI.
  • The use of cryptographic mechanisms, the inclusion of the AMF Identifier, and the overall design of the SUCI contribute to enhanced security and privacy.

7. Security Considerations:

  • The use of SUCI is designed to balance the need for subscriber identity concealment with the security requirements of the 5G network.
  • Security considerations include protecting against identity theft, unauthorized tracking, and other potential security threats.

In summary, the Subscription Concealed Identifier (SUCI) in 5G is a mechanism designed to conceal the subscriber's permanent identity during certain procedures while ensuring secure and authenticated communication with the network. It involves the use of cryptographic techniques and includes components such as the PLMN Identity, AMF Identifier, and the SUPI, contributing to improved security and privacy in the 5G ecosystem.