ARITHMETIC UNIT, ARITHMETIC METHOD, COMPUTER PROGRAM, AND STREAM ENCRYPTION DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent confidential information itself from being stored in a register to be used during an arithmetic operation. ! SOLUTION: The arithmetic unit includes: an input part 11 for inputting input arithmetic expression information indicating an input arithmetic expression, a mask input value obtained by performing mask-processing to an original input value to be used for the input arithmetic expression by a mask value and the mask value; and a masked arithmetic part 12 for calculating a masked arithmetic expression corresponding to the input arithmetic expression indicated by the input arithmetic expression information by using the mask input value or both the mask input value and the mask value, and for outputting a release mask value to be used for mask release processing of obtaining a masked arithmetic result value and the arithmetic result value of the input arithmetic expression indicated by the input arithmetic expression information from the masked arithmetic result value or