To quickly execute a remainder arithmetic operation and a multiplication remainder arithmetic operation or the like.
An arithmetic unit 1 performs a sum of products arithmetic operation by a Montgomery method. A booth encoding part 20 divides a multiplier Y constituted of a plurality of bits by every two bits, and booth-encodes any value of 0, 1, 2, and 3 of the divided 2 bits into any of -2, -1, 0, 1 and 2. A partial product generating part 400 multiplies the booth-encoded multiplier Y and a multiplicand X to generate a plurality of partial product columns having the value of any of -2X, -X, 0, X and 2X. A partial product adding part 450 operates the padding of the code bits of the plurality of partial product columns to line up the bit positions of the code bits, and sets predetermined constant bits according to predetermined conditions to extend codes, and preliminarily calculates a constant value, and adds the constant value to the addition result of the addition of the plurality of partial product columns, and outputs it as the multiplication result of the multiplier Y and the multiplicand X.
Keiko Hada
Sanmei Takeuchi
Hiroto Yamachi
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