Patent ID: 7003666

Claim:
A tamper-detection-information embedding apparatus for embedding predetermined information for tamper detection in a digital image signal, said apparatus comprising: a band division portion operable to divide the digital image signal into a plurality of frequency bands; an authentication data generation portion operable to generate a pseudo-random number series by using predetermined key data, and to generate authentication data from the pseudo-random number series; a key data embedding portion operable to embed the key data in transform coefficients of a lowest frequency band (hereinafter, referred to as MRA) among the plurality of frequency bands; an authentication data embedding portion operable to embed the authentication data in transform coefficients of the frequency bands exclusive of the MRA (hereinafter, referred to as MRR) among the plurality of frequency bands; and a band synthesis portion operable to reconstruct the digital image signal in which the information has been embedded by using the MRA and the MRR to which data embedding processing is subjected, wherein a set value T and a set value m are predetermined and q is predetermined as a value obtained by dividing a transform coefficient by a predetermined quantization step size, wherein said authentication data embedding portion embeds the authentication data in each transform coefficient of the MRR by comparing an absolute value of the transform coefficient with the set value T, and if the absolute value is less than the set value T, setting the transform coefficient to the set value +m or −m depending on a bit value of the authentication data to be embedded, and if the absolute value is not less than the set value T, setting the transform coefficient to an even or odd integer nearest to the value q depending on the bit value of the authentication data to be embedded, and wherein T is a positive integer and m is an integer not more than T.