Multi-party secure authentication system, authentication server, intermediate server, multi-party secure authentication method, and program

摘要

Even when an intermediate server exists, a plurality of servers simultaneously authenticates a user securely. A user apparatus disperses a password. The user apparatus obtains a ciphertext, which is obtained by encrypting a dispersed value. The intermediate server transmits the ciphertext to an authentication server. The authentication server decrypts the ciphertext to obtain the dispersed value. The authentication server determines a verification value. The authentication server obtains a ciphertext. The intermediate server decrypts the ciphertext to obtain the verification value. The intermediate server verifies whether a sum total of the verification values is equal to 0 or not. The authentication server determines a verification value. The authentication server obtains a ciphertext. The authentication server decrypts the ciphertext to obtain the verification value. The authentication server verifies whether a sum total of the verification values is equal to 0 or not.