Novel Authentication Algorithms for UMTS

Abstract

Authentication process of user in mobile networks is an important issue. Previous standard of telecommunication Global System for Mobile Communication (GSM) has many security weaknesses. Under Third Generation Partnership Project (3GPP), new standard Universal Mobile Telecommunication System is developed. UMTS has removed the security weaknesses of previous standards. However one security loop hole has been revealed in UMTS. It is the sending of International Mobile Subscriber Identity (IMSI) in plain text over the air interface. In this master thesis, different security algorithms have been studied. The main focus is to develop an authentication algorithm that resolves this problem and authenticates the user securely and more efficiently. Asymmetric and symmetric cryptographic techniques have been used to resolve this problem. Two security algorithms are introduced in this master thesis for UMTS. First algorithm, which is named as Airam algorithm is based on symmetric and asymmetric cryptographic techniques. In this algorithm it is shown how these two cryptographic techniques can be used together to provide more security to the user. The communication bits and computation complexity have been reduced compare to the GSZV algorithm, hence increasing the efficiency of Airam algorithm. It has also been discussed how effectively this algorithm protects user and data against replay and imposition attacks. The second algorithm which is named as Mutual Authentication Algorithm for UMTS (MAAU). This algorithm is based on symmetric cryptographic technique. In MAAU, a novel technique which uses sequence number in conjunction with secret key has been used. By using this technique the number of transmitting bits over the air interface has been reduced and freshness of each message is assured. In addition, there is no need to check the sequence number for message freshness. This in turns increases the efficiency of the algorithm and improves the security of user and data against replay and imposition attacks. The simulation and results of Airam and MAAU algorithms have been compared with GSZV algorithm to show the proposed algorithms give better performance in term of efficiency while providing defense against replay and imposition attacks.