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44 lines
1.3 KiB
C++
44 lines
1.3 KiB
C++
/*
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* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <LibCrypto/BigInt/UnsignedBigInteger.h>
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namespace Crypto::NumberTheory {
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UnsignedBigInteger Mod(UnsignedBigInteger const& a, UnsignedBigInteger const& b);
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UnsignedBigInteger ModularInverse(UnsignedBigInteger const& a_, UnsignedBigInteger const& b);
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UnsignedBigInteger ModularPower(UnsignedBigInteger const& b, UnsignedBigInteger const& e, UnsignedBigInteger const& m);
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// Note: This function _will_ generate extremely huge numbers, and in doing so,
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// it will allocate and free a lot of memory!
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// Please use |ModularPower| if your use-case is modexp.
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template<typename IntegerType>
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static IntegerType Power(IntegerType const& b, IntegerType const& e)
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{
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IntegerType ep { e };
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IntegerType base { b };
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IntegerType exp { 1 };
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while (!(ep < IntegerType { 1 })) {
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if (ep.words()[0] % 2 == 1)
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exp.set_to(exp.multiplied_by(base));
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// ep = ep / 2;
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ep.set_to(ep.shift_right(1));
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// base = base * base
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base.set_to(base.multiplied_by(base));
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}
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return exp;
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}
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UnsignedBigInteger GCD(UnsignedBigInteger const& a, UnsignedBigInteger const& b);
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UnsignedBigInteger LCM(UnsignedBigInteger const& a, UnsignedBigInteger const& b);
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}
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