| 摘要 |
PURPOSE:To sufficiently secure the privacy of a communication information with less quantity of hardwares and algorithm by generating a key for privacy at each subscriber's terminal to supply it to the central unit individually. CONSTITUTION:From a subscriber's terminal 1, an encipherment key for privacy generated by an encipherment key generation circuit 18 is transmitted to the central unit 2 through a control signal processing circuit 14, and simultaneously an encipherment device 19 ciphers an information signal to be transmitted to the central unit 2 based on the encipherment key, and also, an encipherment communication signal from the unit 2 is decoded by a decoder 20 based on the encipherment key. Simultaneously, in the unit 2, a transmitted encipherment key is received by a control signal processing circuit 24, and the key if stored in an encipherment key holding circuit 27. An information signal ciphered and transmitted is decoded by a decoder 28 and fetched. The encipherment device 29 ciphers an information signal based on the encipherment key held in the circuit 27 then transmits it to the terminal 1. In such a way, the privacy of a communication information can be effectively attained. |
