LibCrypto: Move GCD to method of UnsignedBigInteger

Having it as a method instead of a free function is necessary for the
next commits and generally allows for optimizations that require deeper
access into the `UnsignedBigInteger`.

Libraries/LibCrypto/BigFraction/BigFraction.cpp

@@ -221,7 +221,7 @@ BigFraction BigFraction::rounded(unsigned rounding_threshold) const
 
 void BigFraction::reduce()
 {
-    auto const gcd = NumberTheory::GCD(m_numerator.unsigned_value(), m_denominator);
+    auto const gcd = m_numerator.unsigned_value().gcd(m_denominator);
 
     if (gcd == 1)
         return;

Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp

@@ -547,6 +547,19 @@ FLATTEN UnsignedDivisionResult UnsignedBigInteger::divided_by(UnsignedBigInteger
     return UnsignedDivisionResult { quotient, remainder };
 }
 
+FLATTEN UnsignedBigInteger UnsignedBigInteger::gcd(UnsignedBigInteger const& other) const
+{
+    UnsignedBigInteger temp_a { *this };
+    UnsignedBigInteger temp_b { other };
+    UnsignedBigInteger temp_quotient;
+    UnsignedBigInteger temp_remainder;
+    UnsignedBigInteger output;
+
+    UnsignedBigIntegerAlgorithms::destructive_GCD_without_allocation(temp_a, temp_b, temp_quotient, temp_remainder, output);
+
+    return output;
+}
+
 u32 UnsignedBigInteger::hash() const
 {
     if (m_cached_hash != 0)

Libraries/LibCrypto/BigInt/UnsignedBigInteger.h

@@ -109,6 +109,7 @@ public:
     [[nodiscard]] UnsignedBigInteger as_n_bits(size_t n) const;
     [[nodiscard]] UnsignedBigInteger multiplied_by(UnsignedBigInteger const& other) const;
     [[nodiscard]] UnsignedDivisionResult divided_by(UnsignedBigInteger const& divisor) const;
+    [[nodiscard]] UnsignedBigInteger gcd(UnsignedBigInteger const& other) const;
 
     [[nodiscard]] ErrorOr<UnsignedBigInteger> try_bitwise_not_fill_to_one_based_index(size_t) const;
     [[nodiscard]] ErrorOr<UnsignedBigInteger> try_shift_left(size_t num_bits) const;

Libraries/LibCrypto/CMakeLists.txt

@@ -26,7 +26,6 @@ set(SOURCES
     Hash/PBKDF2.cpp
     Hash/SHA1.cpp
     Hash/SHA2.cpp
-    NumberTheory/ModularFunctions.cpp
     PK/RSA.cpp
     PK/EC.cpp
     SecureRandom.cpp

Libraries/LibCrypto/NumberTheory/ModularFunctions.cpp

@@ -1,28 +0,0 @@
-/*
- * Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#include <AK/Debug.h>
-#include <AK/Random.h>
-#include <LibCrypto/BigInt/Algorithms/UnsignedBigIntegerAlgorithms.h>
-#include <LibCrypto/NumberTheory/ModularFunctions.h>
-#include <LibCrypto/SecureRandom.h>
-
-namespace Crypto::NumberTheory {
-
-UnsignedBigInteger GCD(UnsignedBigInteger const& a, UnsignedBigInteger const& b)
-{
-    UnsignedBigInteger temp_a { a };
-    UnsignedBigInteger temp_b { b };
-    UnsignedBigInteger temp_quotient;
-    UnsignedBigInteger temp_remainder;
-    UnsignedBigInteger output;
-
-    UnsignedBigIntegerAlgorithms::destructive_GCD_without_allocation(temp_a, temp_b, temp_quotient, temp_remainder, output);
-
-    return output;
-}
-
-}

Libraries/LibCrypto/NumberTheory/ModularFunctions.h

@@ -34,6 +34,4 @@ static IntegerType Power(IntegerType const& b, IntegerType const& e)
     return exp;
 }
 
-UnsignedBigInteger GCD(UnsignedBigInteger const& a, UnsignedBigInteger const& b);
-
 }

Meta/gn/secondary/Userland/Libraries/LibCrypto/BUILD.gn

@@ -36,7 +36,6 @@ shared_library("LibCrypto") {
     "Hash/MD5.cpp",
     "Hash/SHA1.cpp",
     "Hash/SHA2.cpp",
-    "NumberTheory/ModularFunctions.cpp",
     "PK/RSA.cpp",
     "SecureRandom.cpp",
   ]