00001
00002
00003 #include "pch.h"
00004 #include "rc5.h"
00005 #include "misc.h"
00006
00007 NAMESPACE_BEGIN(CryptoPP)
00008
00009 void RC5::Base::UncheckedSetKey(CipherDir direction, const byte *k, unsigned int keylen, unsigned int rounds)
00010 {
00011 AssertValidKeyLength(keylen);
00012 AssertValidRounds(rounds);
00013
00014 r = rounds;
00015 sTable.New(2*(r+1));
00016
00017 static const RC5_WORD MAGIC_P = 0xb7e15163L;
00018 static const RC5_WORD MAGIC_Q = 0x9e3779b9L;
00019 static const int U=sizeof(RC5_WORD);
00020
00021 const unsigned int c = STDMAX((keylen+U-1)/U, 1U);
00022 SecBlock<RC5_WORD> l(c);
00023
00024 GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen);
00025
00026 sTable[0] = MAGIC_P;
00027 for (unsigned j=1; j<sTable.size();j++)
00028 sTable[j] = sTable[j-1] + MAGIC_Q;
00029
00030 RC5_WORD a=0, b=0;
00031 const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c);
00032
00033 for (unsigned h=0; h < n; h++)
00034 {
00035 a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3);
00036 b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
00037 }
00038 }
00039
00040 typedef BlockGetAndPut<RC5::RC5_WORD, LittleEndian> Block;
00041
00042 void RC5::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
00043 {
00044 const RC5_WORD *sptr = sTable;
00045 RC5_WORD a, b;
00046
00047 Block::Get(inBlock)(a)(b);
00048 a += sptr[0];
00049 b += sptr[1];
00050 sptr += 2;
00051
00052 for(unsigned i=0; i<r; i++)
00053 {
00054 a = rotlMod(a^b,b) + sptr[2*i+0];
00055 b = rotlMod(a^b,a) + sptr[2*i+1];
00056 }
00057
00058 Block::Put(xorBlock, outBlock)(a)(b);
00059 }
00060
00061 void RC5::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
00062 {
00063 const RC5_WORD *sptr = sTable.end();
00064 RC5_WORD a, b;
00065
00066 Block::Get(inBlock)(a)(b);
00067
00068 for (unsigned i=0; i<r; i++)
00069 {
00070 sptr-=2;
00071 b = rotrMod(b-sptr[1], a) ^ a;
00072 a = rotrMod(a-sptr[0], b) ^ b;
00073 }
00074 b -= sTable[1];
00075 a -= sTable[0];
00076
00077 Block::Put(xorBlock, outBlock)(a)(b);
00078 }
00079
00080 NAMESPACE_END