An image forming apparatus associates a plurality of pieces of user information with a single user identifier, and furthermore, stores keys corresponding to keys that are used for signing in association with the respective pieces of user information. Furthermore, when a user uses the image forming apparatus, jobs for which user information attached to the jobs matches user information that is identified when the user uses the image forming apparatus are extracted, signature verification is performed on respective pieces of signature data attached to the extracted jobs, using the keys held in a user information table, and jobs that are successfully verified are further extracted and listed.