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

摘要

A digital image signal is 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.