Patent ID: 8365265

Claim:
An image forming apparatus which can communicate, through a communication medium, with an authenticating server having a storing unit in which user information for identifying a user and first authentication information included in a plurality of storage media have been stored in correspondence to each other, comprising: a computer configured to implement: an authentication information receiving unit configured to receive, from the authenticating server, first authentication information which was made to correspond to user information input to the image forming apparatus; a first authentication information specifying unit configured to specify the first authentication information which does not coincide with second authentication information which is obtained by reading a storage medium that is owned by the user and is used for user authentication and which is included in the storage medium; a deleting request transmitting unit configured to transmit a deleting request including the first authentication information specified by the first authentication information specifying unit to the authenticating server; a second authentication information specifying unit configured to specify the first authentication information which coincides with the second authentication information which is obtained by reading the storage medium that is owned by the user and is used for the user authentication and which is included in the storage medium; and a stocktaking request transmitting unit configured to transmit a stocktaking request including the first authentication information specified by the second authentication information specifying unit to the authenticating server, wherein the first authentication information included in the deleting request is the first authentication information whose stocktaking is not performed by the stocktaking request.