An object of the present invention is to prevent secret information that is
being internally processed from being inferred through operational
information of a secured device, including the current consumption
information. One solution is provided by an information processing device
having at least a key generation apparatus that generates key data
automatically, an encryption unit that encrypts data with the
corresponding key data, a register that stores a plurality of encrypted
data items with the corresponding encryption key data items, and an
arithmetic unit that performs operations using data expressed with the
corresponding encryption key data and new key data as the input, encrypts
the operation result with new input key data, and outputs the result,
thereby being capable of performing internal processing on an encrypted
data expression. Accordingly, only encrypted data is transferred on the
internal or external data bus line.
