A public key signature for authentication in telephone

This paper presents an authentication method for telephone signals using a public key signature. An analog telephone signal needs a special signature which is robust to noise and other disturbances in the telephone line. The signature is generated from some part of the telephone signal using a robust Hash function. The Hash function works by projecting some parts of the telephone signal to N patterns of pseudo noise to produce Hash bits. The output of the Hash function is encrypted using RSA as the signature and then inserted into some other part of the telephone signal as a watermark using spread spectrum modulation without disturbing the conversation. This paper also discusses the possibility of producing false telephone conversation and the robustness of the signature.