Encryption apparatus.

摘要

The present invention concerns encryption apparatus mainly intended for encrypting speech signals. The apparatus comprises means (10) for sampling a signal to be encrypted at two differing rates, and for reading the sampled signal into storage means (20) at one of said rates and reading it out of said storage means at the other of said rates so that the signal is alternately dispersed upwardly and downwardly with each pair of upward and downward dispersion representing a frame. To improve security the apparatus further includes means for generating a pseudo random binary number, means (53) for defining a superframe structure consisting of a predetermined number of said frames, and means (50, 51) operative to set the starting point of each individual superframe as an upward or a downward dispersion in dependence on the next digit of said pseudo-random binary number.