01670nas a2200205   4500000000100000000000100001008004100002260000900043653001900052653002800071653001100099653000800110653001200118653001300130100001700143245005200160300001000212490000600222520123600228       2000                            d  c200010aauthentication10acellular communications10acoding10aGSM10asecrecy10asecurity1 aMetodi Popov00aSecurity Aspects of the Cellular Communications  a73-940 v43 a<p>This article describes the basic principles and approaches used in cellular communications to guarantee protection of voice and data massages, connections, network and system equipment. It is well known that Public Land Mobile Networks (PLMN) needs a higher level of protection than traditional telecommunication networks. The second generation cellular systems as a kind of mobile digital radio systems allow to guarantee the so called information and subscriber security to their users discussed in the paper as secrecy and authentication. In the second generation cellular systems the terms “security” and “protection” (based on the GSM-standard) mean preventing unauthorized use of the system resources and ensuring secrecy of conversations (based on RSA-algorithm) between mobile users. In this aspect, the author describes the following approach to protection and security: authentication; secrecy of transmitted voice and data; secrecy of subscriber; secrecy of equipment; secrecy of connections; and secrecy of signals for command and control. Because in wider sense the term security includes also error protection of information, various standards for coding in cellular systems are described and compared.</p>