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external/crypto++-5.6.3/rc5.cpp

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+// rc5.cpp - written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+#include "rc5.h"
+#include "misc.h"
+#include "secblock.h"
+
+NAMESPACE_BEGIN(CryptoPP)
+
+void RC5::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs &params)
+{
+	AssertValidKeyLength(keylen);
+
+	r = GetRoundsAndThrowIfInvalid(params, this);
+	sTable.New(2*(r+1));
+
+	static const RC5_WORD MAGIC_P = 0xb7e15163L;    // magic constant P for wordsize
+	static const RC5_WORD MAGIC_Q = 0x9e3779b9L;    // magic constant Q for wordsize
+	static const int U=sizeof(RC5_WORD);
+
+	const unsigned int c = STDMAX((keylen+U-1)/U, 1U);	// RC6 paper says c=1 if keylen==0
+	SecBlock<RC5_WORD> l(c);
+
+	GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen);
+
+	sTable[0] = MAGIC_P;
+	for (unsigned j=1; j<sTable.size();j++)
+		sTable[j] = sTable[j-1] + MAGIC_Q;
+
+	RC5_WORD a=0, b=0;
+	const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c);
+
+	for (unsigned h=0; h < n; h++)
+	{
+		a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3);
+		b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
+	}
+}
+
+typedef BlockGetAndPut<RC5::RC5_WORD, LittleEndian> Block;
+
+void RC5::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
+{
+	const RC5_WORD *sptr = sTable;
+	RC5_WORD a, b;
+
+	Block::Get(inBlock)(a)(b);
+	a += sptr[0];
+	b += sptr[1];
+	sptr += 2;
+
+	for(unsigned i=0; i<r; i++)
+	{
+		a = rotlMod(a^b,b) + sptr[2*i+0];
+		b = rotlMod(a^b,a) + sptr[2*i+1];
+	}
+
+	Block::Put(xorBlock, outBlock)(a)(b);
+}
+
+void RC5::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
+{
+	const RC5_WORD *sptr = sTable.end();
+	RC5_WORD a, b;
+
+	Block::Get(inBlock)(a)(b);
+
+	for (unsigned i=0; i<r; i++)
+	{
+		sptr-=2;
+		b = rotrMod(b-sptr[1], a) ^ a;
+		a = rotrMod(a-sptr[0], b) ^ b;
+	}
+	b -= sTable[1];
+	a -= sTable[0];
+
+	Block::Put(xorBlock, outBlock)(a)(b);
+}
+
+NAMESPACE_END