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79 lines
1.9 KiB
79 lines
1.9 KiB
// rc5.cpp - 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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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()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3); |
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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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