Improve LFSR-based encryption with an extra layer of protection

Encryption coding schemes for asynchronous data used in message/speech communication systems typically employ a linear feedback shift resister (LFSR) based design. LFSR-based design creates a single minimal polynomial pseudorandom bit sequence (PRBS) code, where the keying algorithm is changed periodically to enhance security. In a conventional LFSR-based encryptor, the clock used to run the shift registers and the keying algorithm generator is the same as that recovered from the incoming data. The clock is derived from the incoming data to maintain phase synchronization between the encryption code and the data, and the control code generator selects the sequence of the position of various code patterns. A unique advantage of this approach is that after getting the start signal, all the algorithm generators perform independently.