| 摘要 |
PROBLEM TO BE SOLVED: To make forgery and cryptoanalysis by inference, etc., difficult by embedding an authentication code to authenticate the person himself or herself into a digital image and subjecting the entire part of the digital image to encryption. SOLUTION: Digest data is prepared by subjecting the digital image data over the entire part including the authentication data and other image data to encryption. Unidirectional functions can be used for the encryption. The formed digest data an further encrypted by a receiver's password, etc., to prepare the encrypted digest data. The encrypted digest data are recorded into the original region, thereby, a hardly forgeable digital card including the authentication code and the encrypted digest data in a part of the original image data can be prepared.
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