name: AK
full_form: Anonymity Key
context: procedure, when the HE/AuC receives an authentication data request with a "synchronisation failure indication" and AUTS, the detailed procedure is defined as follows: - MAC-S and SQNMS AK are retrieved from AUTS. - AK is calculated using f5 function with MAC-S as one input. - SQNMS is retrieved by computing SQNMS AK AK. - MAC-S is verified with MAC-S', where MAC-S' = f1*K(SQNMS || RAND || AMF). It means MAC-S is one of the inputs to retrieve SQNMS. SQNMS is one of the inputs to verify MAC-S. The home network knows whether to use MAC-S to calculate AK based on the subscription identifier, e.g. IMSI or SUPI.
description: The Anonymity Key (AK) is a critical parameter used in authentication and security procedures within the telecommunications network. It is calculated using the f5 function with MAC-S as one input, and plays a crucial role in verifying MAC-S and retrieving SQNMS.
explanation: The context explicitly mentions AK being retrieved from AUTS, calculated using the f5 function, and used in verifying MAC-S, which justifies its classification as a Parameter. The detailed procedure outlined in the context highlights the importance of AK in authentication and security processes.
section_title: 6.4.1.2	Solution details
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biotag_Description: O,B-Parameter,I-Parameter,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,O,B-Parameter,O,O,O,O,O,O,O,O,O,O,B-Parameter,O,O,O