An image forming apparatus includes a reader for reading image data from a document. An inherent information storage stores information inherent to the image forming apparatus. An encryption key generator generates an encryption key based on the inherent information in the inherent information storage, and an encryptor encrypts the image data read by the reader based on the encryption key to generate encryption data. An acceptor accepts an image formation designation to form an image on a recording sheet. A decryption key generator generates a decryption key based on the inherent information in the inherent information storage if the image formation designation is accepted by the acceptor. A decryptor decrypts the encryption data based on the decryption key to acquire the image data, and an image forming section forms the image on the recording sheet based on the data acquired by the decryptor.