A cryptosystem using digital signal processors for mobile communication

The authors propose a voice cryptosystem which can be used with the proposed digital mobile communications systems. The voice cryptosystem is based on a pseudonoise (PN) sequence generator. Cryptographic security measures including periodicity and linear complexity of the key stream are analyzed. The cryptographic keys are used as the initial value of linear feedback shift registers (LFSRs) and a control register. The initial value of the control register determines one of a large number of periodic sequences, and the initial values of the LFSR determine the starting point of the periodic sequence. The scheme was shown to be efficiently implemented using software with a digital signal processor