dc1180d6b2
The previous implementation ignored "empty" bigints that represented zero, leading to random crashes.
93 lines
2.6 KiB
C++
93 lines
2.6 KiB
C++
/*
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* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
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* Copyright (c) 2020-2021, Dex♪ <dexes.ttp@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "UnsignedBigIntegerAlgorithms.h"
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namespace Crypto {
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void UnsignedBigIntegerAlgorithms::modular_inverse_without_allocation(
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UnsignedBigInteger const& a,
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UnsignedBigInteger const& b,
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UnsignedBigInteger& temp_1,
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UnsignedBigInteger& temp_2,
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UnsignedBigInteger& temp_3,
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UnsignedBigInteger& temp_4,
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UnsignedBigInteger& temp_minus,
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UnsignedBigInteger& temp_quotient,
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UnsignedBigInteger& temp_d,
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UnsignedBigInteger& temp_u,
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UnsignedBigInteger& temp_v,
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UnsignedBigInteger& temp_x,
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UnsignedBigInteger& result)
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{
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UnsignedBigInteger one { 1 };
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temp_u.set_to(a);
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if (!a.is_odd()) {
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// u += b
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add_into_accumulator_without_allocation(temp_u, b);
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}
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temp_v.set_to(b);
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temp_x.set_to(0);
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// d = b - 1
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subtract_without_allocation(b, one, temp_d);
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while (!(temp_v == 1)) {
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while (temp_v < temp_u) {
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// u -= v
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subtract_without_allocation(temp_u, temp_v, temp_minus);
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temp_u.set_to(temp_minus);
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// d += x
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add_into_accumulator_without_allocation(temp_d, temp_x);
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while (!temp_u.is_odd()) {
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if (temp_d.is_odd()) {
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// d += b
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add_into_accumulator_without_allocation(temp_d, b);
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}
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// u /= 2
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divide_u16_without_allocation(temp_u, 2, temp_quotient, temp_1);
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temp_u.set_to(temp_quotient);
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// d /= 2
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divide_u16_without_allocation(temp_d, 2, temp_quotient, temp_1);
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temp_d.set_to(temp_quotient);
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}
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}
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// v -= u
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subtract_without_allocation(temp_v, temp_u, temp_minus);
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temp_v.set_to(temp_minus);
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// x += d
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add_into_accumulator_without_allocation(temp_x, temp_d);
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while (!temp_v.is_odd()) {
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if (temp_x.is_odd()) {
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// x += b
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add_into_accumulator_without_allocation(temp_x, b);
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}
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// v /= 2
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divide_u16_without_allocation(temp_v, 2, temp_quotient, temp_1);
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temp_v.set_to(temp_quotient);
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// x /= 2
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divide_u16_without_allocation(temp_x, 2, temp_quotient, temp_1);
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temp_x.set_to(temp_quotient);
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}
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}
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// return x % b
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divide_without_allocation(temp_x, b, temp_1, temp_2, temp_3, temp_4, temp_quotient, result);
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}
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}
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