Abstract:

A speech communication system with high security was designed to overcome the trouble of eavesdropping. In this system ,a new 256-bit block cipher-Must 2 and a pseudorandom number generator-Must-Rnd as well as a high-security public key cryptosystem for a session key are employed.Thus,the session key caused by Must-Rnd is transmitted to the far end of the telephone for the real-time speech encryption and decryption by Must2.The proposed system is finally implemented on the TMS320VC5402 Digital Signal Processor(DSP)with good audio quality.

Key words: secure speech communication system, algorithm , block cipher, public key cipher, session key, pseudorandom number generator, digital scrambler