Spectrum Analysis of the Stream Cipher

Abstract

Classical cryptography theory holds that the true random sequence is better than any pseudorandom sequence on the security of stream cipher. So people prefer the pseudorandom sequence with long-period to the pseudorandom sequence with short-period. In this paper, it is proved through power spectrum analysis that the pseudorandom sequence with long-period cant effectively conceal message characteristics in frequency-domain. To combine the pseudorandom sequences with long cycle and short cycle may be the better encryption key.