A Novel Stream Cipher for Cryptographic Applications

This paper presents a novel keystream generator using pseudorandom binary sequences (PRBS) with irregular clocking that is based on the A5/1 stream cipher which is used to secure GSM conversations. An improvement in security is obtained by introducing dynamic polynomial switching in the Linear Feedback Shift Registers (LFSRs) present in the architecture for pseudo noise sequence generation. A basic security analysis shows that this introduction increases the stream cipher´s resistance to cryptanalysis. Statistical tests are applied to the keystream in compliance with the National Institute of Standards and Technology (NIST) and Diehard test suites in order to ensure the quality of bitstream produced by the generator.