220 NS-AKA: An Improved and Efficient AKA Protocol for 3G (UMTS) Networks Neetesh Saxena, Narendra S. Chaudhari Abstract- In this paper, we propose an improved and efficient AKA protocol named “NS-AKA” to prevent the 3G UMTS networks from various attacks like man-in-the-middle attack, redirection attack, replay attack and active attacks in the corrupted UMTS networks. This protocol completely eliminates the need of synchronization between a mobile station and its home network, and protects the actual identity of each user in the networks, (i.e., IMSI) by generating a temporary identity for each user during the authentication. The NS-AKA protocol generates minimum communication and computation overheads compared to UMTS-AKA, S-AKA, AP-AKA, and EURASIP-AKA protocols. On an average the NS-AKA protocol reduces 67% of the bandwidth consumption during the authentication process as compare to UMTS-AKA, which is the maximum reduction of bandwidth by any AKA protocol referred in the paper. Keywords- UMTS, authentication, identity, overhead I. Introduction With the latest and advanced innovations in the mobile applications, the third-generation (3G) technology has been widely used in modern mobile devices. The Universal Mobile Telecommunication System (UMTS) is one of the 3G technologies, which is an extension of Global System for Mobile Communications (GSM). In fact, the UMTS has also been developed into a fourth-generation (4G) technology. There were many security issues in the 2G (GSM) networks and the 3G-UMTS technology has overcome these issues including the mutual authentication. To improve the security weaknesses in the GSM [1], the UMTS authentication and key agreement (AKA) was proposed at the network level for authenticating 3G mobile subscribers. Although, UMTS-AKA has successfully defeated most of the vulnerabilities of GSM but still vulnerable to redirection and man-in-the-middle attack. A. Research Problem The original UMTS-AKA protocol, used to provide authentication between user and the 3G network is vulnerable to some attacks such as redirection attack [5], and man-in-the- middle attack [6]. There are several other issues with the UMTS-AKA including the huge bandwidth usage between the HLR and the VLR, large storage space overhead at the VLR, and synchronization problem. This protocol also generates huge communication and computation overheads in order to provide the mutual authentication between the MS and the VLR/HLR. To solve these issues in the UMTS networks, many researchers have proposed their protocols; however, they are still not able to reduce the overheads effectively. In fact, some of these protocols are still vulnerable to attacks. Neetesh Saxena, Narendra S. Chaudhari Department of CSE, Indian Institute of Technology Indore, India B. Our Contribution Our proposed NS-AKA protocol has the following main attributes: (1) It provides mutual authentication between MS & HLR and between MS & VLR. (2) It prevents the UMTS network from redirection attack (as by AP-AKA, S-AKA), man-in-the-middle attack (as by S-AKA), replay attack (as by UMTS-AKA, S-AKA, AP-AKA, EURASIP-AKA), and active attacks in the corrupted network (as by UMTS-AKA, S-AKA, AP-AKA, EURASIP-AKA). (3) It is able to reduce the bandwidth consumption between VLR and HLR, and reduce the VLR storage. (4) It overcomes the synchronization problem of UMTS-AKA. (5) This protocol hides the actual identity of each mobile station (MS) i.e., IMSI (International Mobile Subscriber Identity) and computes a temporary identity TMSI (Temporary Mobile Subscriber Identity) during the authentication process. The other existing protocols discussed in the paper do not provide identity protection over the network. (6) It generates minimum communication and computation overheads as compare to all existing AKA protocols from the literature. (7) It reduces the bandwidth consumption in the authentication. (8) It is able to lower the ratio of messages exchanged during authentication as compare to UMTS-AKA, AP-AKA, EURASIP-AKA, and S-AKA. TABLE I. SYMBOLS AND ABBREVIATIONS II.Review: Existing AKA Protocols In the UMTS-AKA protocol, each mobile station (MS), shares a secret key SK and certain cryptographic functions with the home network (HLR). The HLR and the MS, each maintains a counter to prevent replay attacks. The cryptographic functions shared between the HLR and the MS include two message authentication codes f1 and f2 and three Proc. of the Intl. Conf. on Advances in Computer Science and Electronics Engineering -- CSEE 2014 Copyright © Institute of Research Engineers and Doctors. All rights reserved. ISBN: 978-1-63248-000-2 doi: 10.15224/ 978-1-63248-000-2-74