Crypto++
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00001 // rc5.cpp - written and placed in the public domain by Wei Dai 00002 00003 #include "pch.h" 00004 #include "rc5.h" 00005 #include "misc.h" 00006 00007 NAMESPACE_BEGIN(CryptoPP) 00008 00009 void RC5::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs ¶ms) 00010 { 00011 AssertValidKeyLength(keylen); 00012 00013 r = GetRoundsAndThrowIfInvalid(params, this); 00014 sTable.New(2*(r+1)); 00015 00016 static const RC5_WORD MAGIC_P = 0xb7e15163L; // magic constant P for wordsize 00017 static const RC5_WORD MAGIC_Q = 0x9e3779b9L; // magic constant Q for wordsize 00018 static const int U=sizeof(RC5_WORD); 00019 00020 const unsigned int c = STDMAX((keylen+U-1)/U, 1U); // RC6 paper says c=1 if keylen==0 00021 SecBlock<RC5_WORD> l(c); 00022 00023 GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen); 00024 00025 sTable[0] = MAGIC_P; 00026 for (unsigned j=1; j<sTable.size();j++) 00027 sTable[j] = sTable[j-1] + MAGIC_Q; 00028 00029 RC5_WORD a=0, b=0; 00030 const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c); 00031 00032 for (unsigned h=0; h < n; h++) 00033 { 00034 a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3); 00035 b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b)); 00036 } 00037 } 00038 00039 typedef BlockGetAndPut<RC5::RC5_WORD, LittleEndian> Block; 00040 00041 void RC5::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const 00042 { 00043 const RC5_WORD *sptr = sTable; 00044 RC5_WORD a, b; 00045 00046 Block::Get(inBlock)(a)(b); 00047 a += sptr[0]; 00048 b += sptr[1]; 00049 sptr += 2; 00050 00051 for(unsigned i=0; i<r; i++) 00052 { 00053 a = rotlMod(a^b,b) + sptr[2*i+0]; 00054 b = rotlMod(a^b,a) + sptr[2*i+1]; 00055 } 00056 00057 Block::Put(xorBlock, outBlock)(a)(b); 00058 } 00059 00060 void RC5::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const 00061 { 00062 const RC5_WORD *sptr = sTable.end(); 00063 RC5_WORD a, b; 00064 00065 Block::Get(inBlock)(a)(b); 00066 00067 for (unsigned i=0; i<r; i++) 00068 { 00069 sptr-=2; 00070 b = rotrMod(b-sptr[1], a) ^ a; 00071 a = rotrMod(a-sptr[0], b) ^ b; 00072 } 00073 b -= sTable[1]; 00074 a -= sTable[0]; 00075 00076 Block::Put(xorBlock, outBlock)(a)(b); 00077 } 00078 00079 NAMESPACE_END