| 摘要 |
PROBLEM TO BE SOLVED: To prevent the decryption of the ciphertext formed by using a secret key by the public key corresponding to the secret key of another person by managing the key in such a manner that the public key to the secret key is the key exclusive of the registered keys. SOLUTION: When the public key Vu+1=(xu+1, yu+1) is inputted to a comparison section 12 from the outside, the comparison section 12 reads out the data x1,..., xu stored in a key memory section 11 and compares the same with part xu+1= of the inputted public key. If the part xu+1 of the inputted public key does not exist in the data x1,..., xu stored in the key storage section 11 as a result of the comparison, the comparison section outputs a signal to permit the use of the public key. The comparison section 12 sends xu+1 to the key memory section 11 simultaneously therewith. On the other hand, if the part xu+1 of the public key inputted to the comparison section 12 is equal any of the data x1,..., xu stored in the key storage section 11, the comparison section 12 outputs a signal of not permitting the use by making judgment that the public key Vu+1 is unusable.
|
