| 摘要 |
PROBLEM TO BE SOLVED: To calculate a Montgomery conversion parameter within an arithmetic circuit while suppressing an increase in an area of the arithmetic circuit.SOLUTION: An arithmetic circuit includes: a Montgomery multiplication circuit; and an inverse arithmetic circuit. The arithmetic circuit that executes predetermined processing includes: a first selector that gives 1 to a first input terminal and a second input terminal of the Montgomery multiplication circuit, feeds back an arithmetic result of the Montgomery multiplication circuit to the first input terminal during a calculation period of calculating a Montgomery parameter (RmodN), and that gives predetermined processing data to the first input terminal and the second input terminal during a predetermined processing arithmetic period; a second selector that gives an arithmetic result of the Montgomery multiplication circuit to which the arithmetic result is fed back to the inverse arithmetic circuit during the calculation period, and that gives the predetermined processing data to the inverse arithmetic circuit during the arithmetic period; and a third selector that outputs an arithmetic result of the inverse arithmetic circuit as the Montgomery parameter during a calculation period, and that outputs the arithmetic result of the inverse arithmetic circuit as the predetermined processing data during the arithmetic period. |
