Data encrypting device, data decoding device, image data storing device and image forming apparatus

摘要

In order to encrypt and decode image data at high speed without providing additional special hardware and placing a heavy load on a CPU, image data 10 is compressed by a compression scheme, and a portion of the compressed data 11 is extracted as encryption key data 12 and the portion, from which the encryption key data 12 is extracted, of the compressed data 11 is changed to zero to convert the compressed data 11 to encrypted data 13. The encrypted data 13 cannot be decoded because data in the beginning portion is corrupted. Moreover, since the decoding of the encrypted data is made impossible by utilizing the property of compressed data, the image data can be encrypted and decoded by a simple processing.