US Patent 7609968 Secure analog communication system using time and wavelength scrambling

Described are a secure communications system and method for transmitting analog signals. The secure communications system includes an analog multiplexer, an analog demultiplexer, a plurality of analog communications channels each at a different wavelength, and a pair of sequence logic modules. Analog signals applied to the analog multiplexer are scrambled onto the multiple communications channels. The demultiplexer descrambles the transmitted scrambled signals to reproduce the original analog signals. The sequence logic modules provide a channel selection signal to implement synchronous pseudorandom switching of the analog signals amongst the analog communication channels. The sequence of the switching between analog communications channels can be pseudorandom in sequence and in time. The channel selection signal is responsive to a key shared between the sequence logic modules. An attacker having access to the analog communications channels cannot retrieve the original analog signals without access to the shared key.