| 摘要 |
PROBLEM TO BE SOLVED: To improve tamper resistant against side channel attack of a remainder calculating apparatus. SOLUTION: The remainder calculating apparatus has a calculator that carries out Montgomery multiplication based on either one of a first multiplicand and a second multiplicand, a multiplier and a divisor; a first multiplicand register that stores a calculation result of the Montgomery multiplication as a first multiplicand; a subtractor that subtracts the calculation result of the Montgomery multiplication with the divisor; and a second multiplicand register that stores a subtraction result of the subtractor as a second multiplicand. Further, the remainder calculating apparatus has a selector that outputs either one of a value of the first multiplicand register and a value of the second multiplicand register to the calculator based on a comparison result between the calculation result of the Montgomery multiplication and the divisor. COPYRIGHT: (C)2010,JPO&INPIT
|
