Voice analog encryption is the earliest developed voice security technology since World War II, the advantage is that the algorithm is simple enough to encrypt the speech source. It can achieve an end-to-end encryption communication, and can be used in a variety of voice channels. However the fatal flaw is that it cannot completely disrupt the speech features, there is an obvious intelligibility residue in the encryption communication that can be easily analyzed and cracked. There is no security at all, especially in the face of strong computer processing power, and has gradually out of the market since the 90s of last century.

Digital encryption is currently the most secure information security technology that has been proven, and is also true for voice communications. With the development of communication technology, the telephone has been developed from a single analog phone to mobile phones, IP phones, satellite phones, and can interconnecting and intercommunicating based on unified IP network. However there is a huge technical hurdle to make an encrypted call using digital encryption technique between different types of phone equipment. At present, there is no such a technology can establish a basic data channel between different telephone networks, operators, and various telephone terminals, which supports the reliable transmission of encrypted data. Its root cause is that the only intercommunication element between the various types of phone terminals is audio signals, which are compressed by vocoders. The existing Modem technology cannot do a reliable data transmission based on the lossy of voice channels. This is the problem we develop AMSI to solve.