Differential power analysis of stream ciphers with LFSRs

Side-channel attacks on block ciphers and public key algorithms have been discussed extensively, but only a few systematic studies on the applicability of side-channel attacks to stream ciphers could be found. The objective of the present study is to develop general differential power analysis techniques which can be employed to attack the stream ciphers with linear feedback shift registers. To illustrate the new approach, a common structure of a stream cipher with the basic components is given. Then the approach is employed to analyze the given structure. The results show that the linear feedback shift registers may leak the information of the secret key. The approach is also applied to Crypto-1 and the experimental results show that it is very effective. 28-bit information of the 48-bit secret key can be obtained just by analyzing some power traces. Furthermore, the present work may be helpful in analyzing a variety of stream ciphers with LFSRs.