Hadamard transform application in speech scrambling

Speech scrambling procedures may be considered as typical orthogonal transforms applications. This point of view was rarely applied since all the scramblers were based on the same orthogonal transform-simple permutation of speech components (time segments and/or frequency subbands). This approach is regarded as an insecure speech encryption method and a new speech scrambling concept was proposed, based on Hadamard transform of the speech components. Linear combination of the speech components based on Hadamard matrices instead of conventional permutation gives better cryptographic performance, maintaining all the good features of the scrambling concept. Scrambling procedures are investigated from two points of view: the transform matrix features as well as the transform kernel. This theoretical analysis gives a subtle view to scrambling procedures.