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35 lines
626 B
C++
35 lines
626 B
C++
// gf256.cpp - written and placed in the public domain by Wei Dai
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#include "pch.h"
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#include "gf256.h"
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NAMESPACE_BEGIN(CryptoPP)
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GF256::Element GF256::Multiply(Element a, Element b) const
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{
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word result = 0, t = b;
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for (unsigned int i=0; i<8; i++)
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{
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result <<= 1;
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if (result & 0x100)
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result ^= m_modulus;
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t <<= 1;
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if (t & 0x100)
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result ^= a;
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}
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return (GF256::Element) result;
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}
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GF256::Element GF256::MultiplicativeInverse(Element a) const
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{
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Element result = a;
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for (int i=1; i<7; i++)
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result = Multiply(Square(result), a);
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return Square(result);
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}
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NAMESPACE_END
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