KEY MANAGEMENT SERVER, TERMINAL, KEY SHARING SYSTEM, KEY DISTRIBUTION PROGRAM, KEY RECEPTION PROGRAM, KEY DISTRIBUTION METHOD, AND KEY RECEPTION METHOD

摘要

In the distribution and sharing of an encryption key used when performing encryption communication between a plurality of terminals, the encryption key can be shared without always holding and managing many keys in each terminal. The time required to start the encryption communication between the terminals can be reduced. The portability of the terminals can be improved. A key management server (1) unilaterally broadcasts to each terminal an encryption key that is unique to each group of the terminals that conduct encryption communication. In this case, the key management server (1) unilaterally broadcasts encryption key data obtained by encrypting the encryption key using a device public key that is the public key of a destination terminal. Each terminal acquires and decrypts the encryption key data addressed to itself, thereby obtaining the encryption key.