Patent ID: 7366320

Claim:
A tamper-detecting apparatus comprising: a characteristic information-calculating unit operable to calculate first characteristic information according to a frequency coefficient at a first frequency domain from a plurality of frequency coefficients obtained by a frequency transformation of a digital image signal; a characteristic information-extracting unit operable to extract second characteristic information according to a second frequency coefficient at a second frequency domain from the plurality of frequency coefficients obtained by the frequency transformation of the digital image signal, and operable to extract third characteristic information according to a third frequency coefficient at a third frequency domain from the plurality of frequency coefficients obtained by the frequency transformation of the digital image signal; and a tamper-determining unit operable to calculate a first comparison result obtained by comparing the first characteristic information and the second characteristic information, operable to calculate a second comparison result obtained by comparing the first characteristic information and the third characteristic information, and operable to determine one of a presence of tampering or changing by image processing according to the first comparison result and the second comparison result, wherein: the second frequency domain is different from the first frequency domain; the third frequency domain is different from the first frequency domain and the second frequency domain; the second frequency domain is higher in frequency than the first frequency domain; and the third frequency domain is higher in frequency than the first frequency domain and the second frequency domain.