Patent ID: 8005213

Claim:
A data processing apparatus comprising: an input section, arranged to input information for encryption key generation; a first encryption key generator, arranged to generate a first encryption key from the information for encryption key generation; an image data generator, arranged to generate image data to be stored in a non-transitory storage medium; a session key generator, arranged to generate a session key based on the first encryption key; a first encryption section, arranged to encrypt the image data using the session key a secondary image data generator, arranged to generate secondary image data of the image data; a second encryption key generator, arranged to generate a second encryption key using information secretly held by the data processing apparatus; a second encryption section, arranged to encrypt the secondary image data using the second encryption key; and a controller, arranged to store the image data encrypted by the first encryption section and the secondary image data encrypted by the second encryption section in the non-transitory storage medium, wherein the session key generator generates the session key using the first encryption key and a one-way function, the first time that it generates a session key, and generates the session key using the most recently generated session key and the one-way function, the second and subsequent times that it generates a session key, and destroys the session key which is used to generate a next session key, and wherein if different image data is encrypted, the first encryption section uses a different session key.