Patent ID: 7908411

Claim:
A data transfer device that receives an instruction to transfer first-type data or second-type data, selects and reads one of the first-type data and the second-type data from a memory according to the instruction, performs cryptographic processing on the read one, and writes a result of the cryptographic processing into the memory, the data transfer device comprising: a cryptographic processing unit operable to perform the cryptographic processing on input data and output a result of the cryptographic processing; a transfer unit operable to transfer data between the memory and the cryptographic processing unit; a condition information storage unit storing condition information that is based on a cryptosystem pertaining to the first-type data and used as a criterion of judgment on whether to switch a transfer target from the first-type data to the second-type data; and a judgment unit operable, on receipt of an instruction to transfer the second-type data during the transfer of the first-type data, to make the judgment based on a size of an un-transferred part of the first-type data that has not been transferred and the condition information, wherein the transfer unit switches the transfer target according to the instruction to transfer the second-type data and a result of the judgment.