| 摘要 |
PROBLEM TO BE SOLVED: To provide a falsification position detection method using a weak electronic watermark due to number theoretical transform, and to provide a falsification correction method. SOLUTION: A processing section obtains main key information P for the number theoretical transform and a rootαof an order N using the orders N and the P as a modulus based on P (S101). The processing section inputs each pixel value o<SB>ij</SB>of an original image block o<SB>xy</SB>(S103). The processing section creates signature information s<SB>xy</SB>for embedding in each pixel value o<SB>xy</SB>based on the P (S105). The processing section obtains an embedded image block e<SB>xy</SB>where the signature information is embedded by obtaining the difference between o<SB>xy</SB>and s<SB>xy</SB>(S107). The processing section obtains a number theoretical transform coefficient E<SB>xy</SB>of e<SB>xy</SB>and that O<SB>xy</SB>of the o<SB>xy</SB>(S109, S111). The processing section generates a block K<SB>xy</SB>of subkey information corresponding to each block (S113). The processing section processes each step to the original pixel block o<SB>xy</SB>, obtains e<SB>xy</SB>and K<SB>sy</SB>for storing at a storage section (S115), and transmits e<SB>xy</SB>, P, N, and K<SB>xy</SB>(S117). COPYRIGHT: (C)2004,JPO
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