Abstract: A computer system checks whether or not an authentication success rate for a registered user shows an over-time reduction based on the history of the results of the previous biometric authentication processes in which the high-speed verification process is executed, when the authentication success rate is determined as showing an over-time reduction for the registered user, the computer system instead executes a precise verification process for verifying input biometric information against registered biometric information to make verification with a higher precision than with the high-speed verification process.

Abstract: An image decryption apparatus includes: an interface unit that acquires an encrypted image; and a processor adapted to: specify a block not presenting unevenness in brightness and a block presenting unevenness in brightness, among a plurality of first blocks into which the encrypted image is divided, and generate a decrypted image by moving each pixel of the encrypted image, in accordance with a predetermined rule; select, from among the second blocks located near the block of interest in a plurality of second blocks into which the decrypted image is divided, at least one second block that is included in the block not presenting unevenness in brightness on the encrypted image prior to generation of the decrypted image, as a reference value calculation block; and correcting the value of each pixel included in the block of interest, using the values of pixels included in the reference value calculation block.