APPARATUS FOR EXTRACTING CONFIDENTIAL INFORMATION, APPARATUS FOR REWRITING CONFIDENTIAL INFORMATION AND RESTORATION APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a confidential information extracting apparatus for efficiently extracting confidential information inserted into compressed image data.

SOLUTION: Confidential data-inserted/compressed image data are partially decoded by a partial decoding section 14, extracted by a confidential data extracting section 20 and output as confidential data output. The confidential data extracting section 20 comprises a final non-zero coefficient detecting part 41, an additional coefficient position and amount measuring part 51 and a confidential data determining part 52. In the final non-zero conversion coefficient extracting part 41, a final coefficient is extracted from among non-zero quantization conversion coefficients and in the coefficient position and amount measuring part 51, a position and a value of the final non-zero quantization conversion coefficient are determined. In the confidential data determining part 52, confidential data are determined from the position and the coefficient value.

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