A new speech scrambling method: Comparative analysis and a fast algorithm

Abstract

Conventional speech scrambling concept is based on permutation of time segments and/or frequency subbands. Although this approach is regarded as an insecure speech encryption method, almost all published scramblers are of that type. W e found out that a linear combination based on Hadamardm atrices instead of conventional permutation gives better cryptographic performances, maintaining all the good features of the scrambling concept. The new scrambling method provides a large key space and a simpler key selection. It attainsnegligible residualintelligibility and higher degree of cryptanalytic immunity. The price of these great improvements is a potential complexity increase. That is why we designed a fast algorithm for the new scrambling method.