Patent ID: 7400730

Claim:
A cryptographic communication method for use in a communication network having a plurality of terminal devices, a communication controller associated with a control plane (hereinafter called a “C-Plane”), and a data communication device associated with a user plane (hereinafter called a “U-plane”), in such a manner that said communication controller is separated from said data communication device, wherein at least one secret key is shared between an arbitrary terminal and said data communication unit, said method comprising the steps of: transmitting encryption control information to at least one of said data communication device and said terminal by said communication controller; encrypting U-Plane information to be transmitted to the other party using one of the shared secret keys in accordance with contents of the encryption control information upon receipt of the encryption control information, and adding the encryption control information to the encrypted U-Plane information for transmission to the other party by one of said data communication device and said terminal; and decrypting the encrypted U-Plane information using one of the shared secret keys by said other party upon receipt of the encrypted U-Plane information with the encryption control information added thereto.