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LibCrypto: Add the montgomery modular power algorithm

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This algorithm allows for much faster computations of modular powers
(around a 5x-10x speedup of the Crypto test). However, it is only valid
for odd modulo values, and therefore the old algorithm must be kept for
computations involving even modulo values.
This commit is contained in:
DexesTTP
2021-05-12 22:47:07 +02:00
committed by Linus Groh
parent 5071989545
commit 485adb5e29
5 changed files with 264 additions and 2 deletions
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13
Userland/Libraries/LibCrypto/BigInt/Algorithms/BitwiseOperations.cpp
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@@ -203,7 +203,7 @@ FLATTEN void UnsignedBigIntegerAlgorithms::shift_left_without_allocation(
}
}
ALWAYS_INLINE void UnsignedBigIntegerAlgorithms::shift_left_by_n_words(
void UnsignedBigIntegerAlgorithms::shift_left_by_n_words(
UnsignedBigInteger const& number,
size_t number_of_words,
UnsignedBigInteger& output)
@@ -216,6 +216,17 @@ ALWAYS_INLINE void UnsignedBigIntegerAlgorithms::shift_left_by_n_words(
__builtin_memcpy(&output.m_words.data()[number_of_words], number.m_words.data(), number.m_words.size() * sizeof(unsigned));
}
void UnsignedBigIntegerAlgorithms::shift_right_by_n_words(
UnsignedBigInteger const& number,
size_t number_of_words,
UnsignedBigInteger& output)
{
// shifting right by N words means just not copying the first words
output.set_to_0();
output.m_words.resize_and_keep_capacity(number.length() - number_of_words);
__builtin_memcpy(output.m_words.data(), &number.m_words.data()[number_of_words], (number.m_words.size() - number_of_words) * sizeof(unsigned));
}
/**
* Returns the word at a requested index in the result of a shift operation
*/