Patent ID: 8363839

Claim:
An image forming apparatus, comprising: a first encryption key storing section that is a nonvolatile memory to store a first encryption key, the first encryption key consisting of a part of an original encryption key for encrypting print information; a second encryption key storing section that is an attachable and removable nonvolatile memory to store a second encryption key, the second encryption key consisting of the remainder of the original encryption key; an encryption key generating section that reads the first and second encryption keys from the first and the second encryption key storing sections respectively, and generates the original encryption key from the first encryption key and the second encryption key, and stores the generated original encryption key into a volatile memory; an encryption processing section that reads the generated original encryption key from the volatile memory, and encrypts the print information using the original encryption key, and stores the encrypted print information into a print information storing section; a nonvolatile distinguishment information storing section that stores distinguishment information for distinguishing the image forming apparatus, wherein when the second encryption key storing section is attached, the encryption key generating section judges whether or not the first encryption key is stored in the first encryption key storing section, and: (i) if it is judged that the first encryption key is not stored in the first encryption key storing section, the encryption key generating section obtains the original encryption key from the second encryption key storing section, generates the first and second encryption keys from the obtained original encryption key, stores the first encryption key into the first encryption key storing section, and stores the second encryption key along with the distinguishment information stored in the distinguishment information storing section into the second encryption key storing section, and (ii) if it is judged that the first encryption key is stored in the first encryption key storing section, the encryption key generating section reads the second encryption key and second distinguishment information from the attached second encryption key storing section, and if the second distinguishment information agrees with the distinguishment information stored in the distinguishment information storing section, the encryption key generating section generates the original encryption key from the read second encryption key and the first encryption key stored in the first encryption key storing section, and stores the generated original encryption key into the volatile memory.