// rc5.cpp - written and placed in the public domain by Wei Dai #include "pch.h" #include "rc5.h" #include "misc.h" NAMESPACE_BEGIN(CryptoPP) void RC5::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs ¶ms) { 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