Secure voice (alternatively secure speech or ciphony) is a term in cryptography for devices which are designed to provide voice encryption for voice communication over a range of communication devices such as radio or telephone.

A digital secure voice usually includes two components, a digitizer to convert between speech and digital signals and an encryption system to provide confidentiality. What makes ciphony difficult in practice is a need to send the encrypted signal over the same circuits used to transmit unencrypted voice, e.g. telephones or mobile radios. This leads to the use of vocoders to achieve tight bandwidth compression of the speech signals. NSA's STU-III, KY-57 and FNBDT are examples of systems that operate over existing voice circuits. The STE system, by contrast, requires wide bandwidth ISDN lines for its normal mode of operation.

See also

• Scrambler
• Delilah (secure speech)
• SIGSALY
• Secure Terminal Equipment
• VINSON

References

• Randall K. Nichols and Panos C. Lekkas, Wireless Security: Models, Threats, and Solutions, McGraw-Hill, 2002, chapter 6, "Speech cryptology", ISBN 0071380388.