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LibCrypto: Add extended GCD algorithm

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devgianlu 2024-12-15 16:04:20 +01:00 • committed by Ali Mohammad Pur
parent a74ef5df3d
commit b35764da0e
Notes: github-actions[bot] 2024-12-15 22:32:59 +00:00
2 changed files with 58 additions and 0 deletions
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57
Libraries/LibCrypto/BigInt/Algorithms/GCD.cpp
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@ -1,6 +1,7 @@
/*
* Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
* Copyright (c) 2020-2021, Dex♪ <dexes.ttp@gmail.com>
* Copyright (c) 2024, Altomani Gianluca <altomanigianluca@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -36,4 +37,60 @@ void UnsignedBigIntegerAlgorithms::destructive_GCD_without_allocation(
}
}
void UnsignedBigIntegerAlgorithms::extended_GCD_without_allocation(
UnsignedBigInteger const& a,
UnsignedBigInteger const& b,
UnsignedBigInteger& x,
UnsignedBigInteger& y,
UnsignedBigInteger& gcd,
UnsignedBigInteger& temp_quotient,
UnsignedBigInteger& temp_1,
UnsignedBigInteger& temp_2,
UnsignedBigInteger& temp_shift_result,
UnsignedBigInteger& temp_shift_plus,
UnsignedBigInteger& temp_shift,
UnsignedBigInteger& temp_r,
UnsignedBigInteger& temp_s,
UnsignedBigInteger& temp_t)
{
gcd.set_to(a);
x.set_to(1);
y.set_to(0);
temp_r.set_to(b);
temp_s.set_to_0();
temp_t.set_to(1);
while (temp_r != 0) {
// quotient := old_r div r
divide_without_allocation(gcd, temp_r, temp_quotient, temp_1);
temp_2.set_to(temp_r);
multiply_without_allocation(temp_quotient, temp_r, temp_shift_result, temp_shift_plus, temp_shift, temp_1);
while (gcd < temp_1) {
add_into_accumulator_without_allocation(gcd, b);
}
subtract_without_allocation(gcd, temp_1, temp_r);
gcd.set_to(temp_2);
// (old_s, s) := (s, old_s − quotient × s)
temp_2.set_to(temp_s);
multiply_without_allocation(temp_quotient, temp_s, temp_shift_result, temp_shift_plus, temp_shift, temp_1);
while (x < temp_1) {
add_into_accumulator_without_allocation(x, b);
}
subtract_without_allocation(x, temp_1, temp_s);
x.set_to(temp_2);
// (old_t, t) := (t, old_t − quotient × t)
temp_2.set_to(temp_t);
multiply_without_allocation(temp_quotient, temp_t, temp_shift_result, temp_shift_plus, temp_shift, temp_1);
while (y < temp_1) {
add_into_accumulator_without_allocation(y, b);
}
subtract_without_allocation(y, temp_1, temp_t);
y.set_to(temp_2);
}
}
}