Information-embedding apparatus, encoder, tamper-detecting apparatus, information-embedding method, tamper-detecting method, and recording medium having program recorded therein for executing both of the methods
First Claim
1. 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.
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Accused Products
Abstract
A digital image signal based on transformed in frequency, thereby providing partitioned frequency components. Characteristic information is calculated in accordance with a coefficient at a first frequency domain that is selected from among the partitioned frequency components. A coefficient at a second frequency domain is handled in accordance with predetermined rules, thereby embedding the characteristic information into the coefficient at the second frequency domain. The second frequency domain is selected from among areas that differ from the first frequency domain. The frequency coefficients that exhibit several frequency components are encoded in a predetermined manner, thereby producing compressed image data.
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Citations
13 Claims
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1. A tamper-detecting apparatus comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A tamper-detecting method comprising:
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calculating first characteristic information according to a first frequency coefficient at a first frequency domain from a plurality of frequency coefficients obtained by a frequency transformation of a digital image signal; extracting 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, the second frequency domain being different from the first frequency domain; extracting 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, the third frequency domain being different from the first frequency domain and the second frequency domain; calculating a first comparison result obtained by comparing the first characteristic information and the second characteristic information; calculating a second comparison result obtained by comparing the first characteristic information and the third characteristic information; and determining 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 higher infrequency than the first frequency domain; and the third frequency domain is higher in frequency than the first frequency domain and the second frequency domain.
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13. A computer-readable storage medium having stored thereon a tamper-detecting computer program for causing a computer to execute a method comprising:
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calculating first characteristic information according to a first frequency coefficient at a first frequency domain from a plurality of frequency coefficients obtained by a frequency transformation of a digital image signal; extracting 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, the second frequency domain being different from the first frequency domain; extracting 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, the third frequency domain being different from the first frequency domain and the second frequency domain; calculating a first comparison result obtained by comparing the first characteristic information and the second characteristic information; calculating a second comparison result obtained by comparing the first characteristic information and the third characteristic information; and determining 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 higher infrequency than the first frequency domain; and the third frequency domain is higher in frequency than the first frequency domain and the second frequency domain.
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Specification