To provide the encryption communication system where a transmitter side encrypts information efficiently and the entire system transmits an encrypted text efficiently in the case of transmitting information to plural receivers via a repeater.

A transmitter side 1 transmits a text f(M, K) resulting from encrypting information M by a common key K and plural texts f(K, Ki) resulting from encrypting the common key K with a public key Ki for each of receiver side devices 3-5 to a repeater 2. The repeater 2 transmits the texts f(M, K), f(K, Ki) in pairs to the receivers 3-5. For example, a couple of the texts f(M, K) and f(K, K3) is sent to the receiver 3. The receiver 3 decodes the text f(K, K3) by using a private key to obtain the common key K and decodes the text f(M, K) by using the common key K.