A Survey of Cryptographic Methods in Mobile Network Technologies from 1G to 4G Fredrick Njoroge Email: nfmiringu@gmail.com Telecommunication and Information Engineering Department Jomo Kenyatta University of Agriculture and Technology Lincoln Kamau Email: kamaulincoln@jkuat.ac.ke Telecommunication and Information Engineering Department Jomo Kenyatta University of Agriculture and Technology Abstract – This paper presents a brief overview of the different cryptographic methods used in mobile networks. The focus here is on the mobile communication standards – 1G to 4G. The purpose of this paper is to appreciate the evolution of security measures in mobile networks from 1G to 4G, and examine the cryptosystems in each of the standards. This will be useful to offer a perspective on the development of 5G security. Keywords – DoS, A3, A8, A5/x, IMSI, SRES, RAND, AUTN, authentication triplet, authentication vector, Milenage, SNOW3G, KASUMI, eia, eea I. INTRODUCTION Over the years, there has been a major advancement in wireless communication. This can be pointed out from the inventions and discoveries of the likes of Heinrich Rudolf Hertz, Nikola Tesla and Guglielmo Marconi who are some of the founding fathers of wireless communication [1]. Such led to the development of the standards present today – WiFi, WiMAX, Bluetooth, ZigBee, the first to the fifth generations of mobile networks (1G – 5G) – just to name but a few. However, this “freedom” in telecommunications came along with its insecurity issues, in that wireless communications are prone to security attacks such as eavesdropping, man-in-the-middle attack and denial of service (DoS). Part of the objectives of the evolution of these standards has been to address these security issues so as to provide more secure communication systems. This paper delves into examining each standard, exposing the weaknesses recorded over time and the solutions that have been formulated henceforth to overcome those weaknesses. It is important to recall the features necessary for a wireless communication to be termed as secure [2]:  User authentication – The users are who they claim to be.  Data authentication – Data integrity (the recipient’s assurance that the data has not changed) and data origin authentication (the recipient’s assurance that the data originates from the stated sender).  Data confidentiality – The data is encrypted so that it remains concealed while in transit.  Non-repudiation – This pertains to a service against denial by either party of creating or acknowledging a message.  Authorization – The ability to determine whether an authenticated entity is allowed to execute an action.  Audit – A historical record of events used to determine whether anything has gone wrong, and if so, what it was, when it went wrong and its cause.  Access control – This enables only authorized entities to access resources.  Availability – Resources are accessible and are not prevented from access by malicious entities. II. FIRST GENERATION (1G) MOBILE NETWORKS The first ever mobile networks began around the late 1970s in Tokyo, Japan. Later, Europe (Baltic and Scandinavian countries), the USA and the UK came up with their own 1G systems, namely Nordic Mobile Telephony (NMT), Advanced Mobile Phone Service (AMPS) and Total Access Communication System (TACS) respectively [3]. These systems used