A disclosed image forming apparatus has a cryptographic unit for performing a cryptographic function. The image forming apparatus includes a first managing unit for managing data representing first lists of cryptographic strengths authorized to be used separately for each subject that uses the cryptographic function; and a second managing unit for managing data representing a second list of cryptographic strengths set for the image forming apparatus. The cryptographic unit obtains the first list of the cryptographic strengths authorized to be used for the subject attempting to use the cryptographic function from the first managing unit. The obtained first list of the cryptographic strengths and the second list of the cryptographic strengths are logically multiplied to produce one or more first logical multiplication cryptographic strengths. The one or more first logical multiplication cryptographic strengths are usable to perform the cryptographic function.