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