A new signal encryption technique and its attack study

A novel image and speech signal encryption technique is proposed. The encrypted signal is obtained by scrambling the phase spectrum of the original one. Since the phase spectrum of the original signal is changed, the resulting signal is unrecognized and signal encryption is achieved. The phase spectrum of original signal is modified according to the phase spectrum of pseudonoise. The pseudonoises include m-sequences, Gold code sequences, quasi m-arrays, and Gold code arrays. This type of signal encryption does not increase redundancy in the signal, which resolves the dilemma between data compression and encryption because the compression efficiency of the encrypted signal is increased. The attack study for this type of encryption is also conducted. It is shown that the possibility of a successful attack for a 512×512 encrypted image is 1.25×10 ^-11