Unit using operating system and image forming apparatus using the same

A chip mountable on a customer replaceable unit monitoring memory (CRUM) unit used in an image forming job includes a central processing unit (CPU) with an operating system (OS) thereof, which is separate from an OS of the image forming apparatus, to perform at least one of authentication and cryptographic data communication with a main body of an image forming apparatus by executing one cryptographic algorithm corresponding to a set state from among a plurality of pre-provided cryptographic algorithms, using the OS thereof. The security of a unit on which the chip is mounted can thereby be reinforced and random changes of data of the unit can be prevented.