To reduce processing load or processing time required for compression and encryption of data. Data to be compressed, such as image data, is divided into specified block sizes by am image divider (10). A quantizer (12) references a quantization table (14) to quantize each of these blocks of data. The result of this quantization is entropy encoded by an entropy encoder (16) referencing a coding table (18) to acquire compressed data. An encryptor (20) encrypts the quantization table (14) and coding table (18) used in the quantization and encoding using a specified encryption method. A multiplexor (24) gathers together the encrypted data acquired as a result together with the compressed data in a specified format.