1// rc5.cpp - written and placed in the public domain by Wei Dai 2 3#include "pch.h" 4#include "rc5.h" 5#include "misc.h" 6 7NAMESPACE_BEGIN(CryptoPP) 8 9void RC5::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs ¶ms) 10{ 11 AssertValidKeyLength(keylen); 12 13 r = GetRoundsAndThrowIfInvalid(params, this); 14 sTable.New(2*(r+1)); 15 16 static const RC5_WORD MAGIC_P = 0xb7e15163L; // magic constant P for wordsize 17 static const RC5_WORD MAGIC_Q = 0x9e3779b9L; // magic constant Q for wordsize 18 static const int U=sizeof(RC5_WORD); 19 20 const unsigned int c = STDMAX((keylen+U-1)/U, 1U); // RC6 paper says c=1 if keylen==0 21 SecBlock<RC5_WORD> l(c); 22 23 GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen); 24 25 sTable[0] = MAGIC_P; 26 for (unsigned j=1; j<sTable.size();j++) 27 sTable[j] = sTable[j-1] + MAGIC_Q; 28 29 RC5_WORD a=0, b=0; 30 const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c); 31 32 for (unsigned h=0; h < n; h++) 33 { 34 a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3); 35 b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b)); 36 } 37} 38 39typedef BlockGetAndPut<RC5::RC5_WORD, LittleEndian> Block; 40 41void RC5::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const 42{ 43 const RC5_WORD *sptr = sTable; 44 RC5_WORD a, b; 45 46 Block::Get(inBlock)(a)(b); 47 a += sptr[0]; 48 b += sptr[1]; 49 sptr += 2; 50 51 for(unsigned i=0; i<r; i++) 52 { 53 a = rotlMod(a^b,b) + sptr[2*i+0]; 54 b = rotlMod(a^b,a) + sptr[2*i+1]; 55 } 56 57 Block::Put(xorBlock, outBlock)(a)(b); 58} 59 60void RC5::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const 61{ 62 const RC5_WORD *sptr = sTable.end(); 63 RC5_WORD a, b; 64 65 Block::Get(inBlock)(a)(b); 66 67 for (unsigned i=0; i<r; i++) 68 { 69 sptr-=2; 70 b = rotrMod(b-sptr[1], a) ^ a; 71 a = rotrMod(a-sptr[0], b) ^ b; 72 } 73 b -= sTable[1]; 74 a -= sTable[0]; 75 76 Block::Put(xorBlock, outBlock)(a)(b); 77} 78 79NAMESPACE_END 80