1. An encryption apparatus comprising: an input unit which inputs original data; a division unit which divides the input original data into at least one data block; an authentication data generation unit which generates authentication data using a fist encryption key for the data block; a combining unit which combines the authentication data to the data block; an encryption unit which generates encrypted data using a second encryption key for the data block combined with the authentication data; and an output unit which outputs the encrypted data, wherein a size of the data block is an integer multiple of a bank size of a rewritable non-volatile memory equipped in a decryption apparatus.