An image verification system includes an imaging device and a first image verification device. The imaging device has an image generating unit which generates image data, and a first verification data generating unit which generates first verification data using the image data and common information. In the first image verification device, a first verification unit verifies whether or not the image data is modified using the image data, the first verification data, and the common information. If it is verified by the first verification unit the image data is not modified, an embedding unit embeds watermark data to detect a modified portion of the image data in order to generate watermarked image data. A second verification data generating unit generates second verification data using the watermarked image data and secret information.

A digital signature generating apparatus generates a digital signature of digital data. The digital signature generating apparatus includes a receiving unit, the secret key changing unit and a digital signature generating unit. The receiving unit receives one of a first command and a second command. The first command includes information indicating one of a plurality of secret keys, and the plurality of secret keys are included in the digital signature generating apparatus. The secret key changing unit changes a secret key used by the digital signature generating apparatus to a secret key specified by the first command, if the first command is received by the receiving unit. The digital signature generating unit generates the digital signature of the digital data from a hash value extracted from the second command, if the second command is received by the receiving unit.

An image verification system includes an image generation apparatus and a first verification apparatus. The image generation apparatus (a) generates image data, (b) generates a hash value from the image data, and (c) generates first verification data from the hash value using a common key cryptography and not using a public key cryptography. The first verification apparatus (a) receives the hash value and the first verification data, (b) verifies, using the received hash value, the received first verification data and the common key cryptography, whether the image data is altered, and (c) generates second verification data from the hash value using the public key cryptography, if the first verification apparatus verifies that the image data is not altered.