| 摘要 |
PURPOSE:To prevent illegal use and illegal charging without providing much hint to the analysis of a terminal program by preventing generation of a dummy key center/terminal equipment. CONSTITUTION:When a ciphered key is required, a terminal equipment uses a ciphering device 61 to cipher a random number K3 based on an open public key K2e to send the result as a ciphering key request signal, a key center uses a secret key K2d to decode the random number K3 at a decoder 21 and the random number K4 is ciphered by a ciphering device 22 based on the random number K3 and the ciphered signal is sent to the terminal equipment. The terminal equipment decodes the random number K4 based on the random number K3 and the random number K3 is given to a prescribed multi-value function section 53, from which one output K3' is obtained, the random numbers K4, K3' are ciphered by using the open public key 2d and a reply signal is sent to the key center. The key center decodes the random numbers K4, K3' based on a secret key K2d, the coincidence with the K4 generated before is confirmed, the random number K3 is given to the multi-function section 53, in which the presence of the random number K3' is confirmed, and only when the confirmation is taken, the ciphering key is extracted and the ciphering key is ciphered base on the random numbers K4, K3' and the ciphered key is transmitted to the terminal equipment, in which the ciphered key is decoded based on the random numbers K4, K3'. |
