A review of selective analogue methods of speech encryption

Analog encryption schemes are relatively insecure compared to digital encryption schemes, but have an advantage in that they can be easily inter-faced with the existing channels such as telephone, satellite and mobile communication links. In this paper, we present a comprehensive review of selective Speech Encryption techniques. We present a review of mainly analogue encryption techniques. The main reasons for the vulnerability of analog encryption schemes are the bandwidth constraints of the analog channels, the nature of the speech signal and the various encryption schemes which involve permutations as a key to hide the signal.