| 摘要 |
<p>A group signature system includes a user device (400) registered in a group. On receiving an issuing device public key of a set containing the order N of a cyclic group and the elements a_0, a_1, and a_2, the user device (400) so determines prime numbers e, e' that the remainder of the subtraction of a constant smaller than the prime number e from the prime number e is the prime number e', creates a user device secret key of a set containing a number x and a number r such that the product of the product of the results of modulo exponentiation of a_0 and a-1 with a number x and the result of modulo exponentiation of a_2 with a number r is equal to an element A to the e-th power of the first cyclic group when the order N is the modulus and a user device public key of a set containing the prime number e, prime number e', and the element A, transmits the prime number e to an invalidation managing device (300), receives B computed from the prime number e' from the invalidation managing device (300), writes a signature sentence for an inputted message by using the value of B, the user device public key, the user device secret key, and the message, and transmits the message and its signature sentence to a validation device (500).</p> |
