Patent ID: 7310429
Filing Date: 2007-12-18
Classification: G06T,H04N

Abstract:
1. An unauthorized-alteration detecting method comprising: a step in which a processing section specifies a modulus P, an order N which is an even number equal to or larger than 2, and a root α, which are parameters of number theoretic transform; a step in which the processing section reads from a storage section an original-image block f a step in which the processing section uses the modulus P, the order N, and the root α specified, to apply the number theoretic transform to the original-image block f a step in which the processing section determines an embedding position (x′, y′) of a signature image in each block according to a predetermined randomizing function which uses information of a left adjacent block, a right adjacent block, or a surrounding predetermined block as a parameter; a step in which the processing section reads from the storage section a pixel value g a step in which the processing section obtains an integer having the minimum absolute value and satisfying F a step in which the processing section adds or subtracts the embedding amount δ to or from the number-theoretic-transformed block F a step in which the processing section applies inverse number theoretic transform to the number-theoretic-transformed block H a step in which the processing section obtains the embedding-applied-image block h