在通信网络的两端，双方约定一致的Key，在通信的源点用Key对核心数据进行DES加密，然后以密码形式在公共通信网（如电话网）中传输到通信网络的终点，数据到达目的地后，用同样的Key对密码数据进行解密，便再现了明码形式的核心数据。这样，便保证了核心数据在公共通信网中传输的安全性和可靠性。-communications networks in the two ends, the two sides agreed unanimously the Key, In communications with the source Key to the core DES data encryption, Then a password in the form of public communication networks (such as the telephone network) transmission of the communication network in the end, data arrived at their destination, Key used the same password for data decryption, it depicts the code forms the core data. This will ensure that the core data in the public telecommunication network transmission security and reliability.