M. Zhang (USA)
3G, Wireless Networks, Network Security
This paper provides further enhancement on the authen tication and key agreement (AKA) protocol developed for Universal Mobile Telecommunication System (UMTS). UMTS security is based on GSM security and provides sig nificant enhancement to address and correct real and per ceived weaknesses in GSM. As in GSM, the serving net work authenticates the user by using authentication data, called authentication vectors, transferred from the user’s home environment. In each authentication vector, a se quence number is included, which is used by the user to verify the freshness of agreed cipher and integrity keys. To facilitate sequence number generation and verification, two counters are maintained for each user: one in the user side and another in the home environment. This arrange ment however presents a unique challenge to the opera tion of the UMTS AKA, that is, the synchronization be tween the two counters. This paper examines issues in troduced by the synchronization requirement, especially the operational difficulties involved in re-synchronization and sequence number management. To eliminate the re synchronization requirement for the UMTS AKA, an en hanced AKA is proposed in this paper. It is shown that the enhanced AKA is robust in supporting various usage sce narios of the protocol. Moreover, it is also shown that the risk of active attacks is greatly reduced for the enhanced AKA in comparison with the UMTS AKA.
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