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1 files changed, 34 insertions, 0 deletions

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