PURPOSE: To perform protection for the reproduction of image data by performing an arithmetic operation between compression-encoded image data and identification information, and recording a result on a recording medium.

CONSTITUTION: A system control part 28 inputs orthogonally transformed and compressed data to the input 24 of an interface 26, and outputs a password signal to the output 48 of a password encoder 46 synchronizing with the above input. The interface 26 performs a bit inversion arithmetic operation in accordance with the password signal on the first several bytes of the image data outputted from an encoder circuit 22, and writes the image data that is the result of the above operation on the null storage area of a memory card 80. In such a way, the image data in the memory card 80 on which protective recording is performed by a password can be reproduced by a reproducing device on which the same password can be set.