Performance and Statistical Analysis of Stream ciphers in GSM Communications

Abstract

For a stream cipher to be secure, the keystreamgenerated by it should be uniformly random with parameter 1/2.Statistical tests check whether the given sequence follow a certainprobability distribution. In this paper, we perform a detailedstatistical analysis of various stream ciphers used in GSM 2G,3G, 4G and 5G communications. The sequences output by theseciphers are checked for randomness using the statistical testsdefined by the NIST Test Suite. It should also be not possibleto derive any information about secret key and the initial state ofthe cipher from the keystream. Therefore, additional statisticaltests based on properties like Correlation between Keystreamand Key, and Correlation between Keystream and IV are alsoperformed. Performance analysis of the ciphers also has beendone and the results tabulated. Almost all the ciphers pass thetests in the NIST test suite with 99% confidence level. For A5/3stream cipher, the correlation between the keystream and key ishigh and correlation between the keystream and IV is low whencompared to other ciphers in the A5 family.

Keywords

• stream ciphers
• nist
• statistical randomness testing
• gsm
• correlation
• encryption
• keystream