1 // rc6.cpp - written and placed in the public domain by Sean Woods
2 // based on Wei Dai's RC5 code.
3
4 #include "pch.h"
5 #include "rc6.h"
6 #include "misc.h"
7 #include "secblock.h"
8
NAMESPACE_BEGIN(CryptoPP)9 NAMESPACE_BEGIN(CryptoPP)
10
11 void RC6::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs ¶ms)
12 {
13 AssertValidKeyLength(keylen);
14
15 r = GetRoundsAndThrowIfInvalid(params, this);
16 sTable.New(2*(r+2));
17
18 static const RC6_WORD MAGIC_P = 0xb7e15163L; // magic constant P for wordsize
19 static const RC6_WORD MAGIC_Q = 0x9e3779b9L; // magic constant Q for wordsize
20 static const int U=sizeof(RC6_WORD);
21
22 const unsigned int c = STDMAX((keylen+U-1)/U, 1U); // RC6 paper says c=1 if keylen==0
23 SecBlock<RC6_WORD> l(c);
24
25 GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen);
26
27 sTable[0] = MAGIC_P;
28 for (unsigned j=1; j<sTable.size();j++)
29 sTable[j] = sTable[j-1] + MAGIC_Q;
30
31 RC6_WORD a=0, b=0;
32 const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c);
33
34 for (unsigned h=0; h < n; h++)
35 {
36 a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3);
37 b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
38 }
39 }
40
41 typedef BlockGetAndPut<RC6::RC6_WORD, LittleEndian> Block;
42
ProcessAndXorBlock(const byte * inBlock,const byte * xorBlock,byte * outBlock) const43 void RC6::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
44 {
45 const RC6_WORD *sptr = sTable;
46 RC6_WORD a, b, c, d, t, u;
47
48 Block::Get(inBlock)(a)(b)(c)(d);
49 b += sptr[0];
50 d += sptr[1];
51 sptr += 2;
52
53 for(unsigned i=0; i<r; i++)
54 {
55 t = rotlFixed(b*(2*b+1), 5);
56 u = rotlFixed(d*(2*d+1), 5);
57 a = rotlMod(a^t,u) + sptr[0];
58 c = rotlMod(c^u,t) + sptr[1];
59 t = a; a = b; b = c; c = d; d = t;
60 sptr += 2;
61 }
62
63 a += sptr[0];
64 c += sptr[1];
65
66 Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
67 }
68
ProcessAndXorBlock(const byte * inBlock,const byte * xorBlock,byte * outBlock) const69 void RC6::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
70 {
71 const RC6_WORD *sptr = sTable.end();
72 RC6_WORD a, b, c, d, t, u;
73
74 Block::Get(inBlock)(a)(b)(c)(d);
75
76 sptr -= 2;
77 c -= sptr[1];
78 a -= sptr[0];
79
80 for (unsigned i=0; i < r; i++)
81 {
82 sptr -= 2;
83 t = a; a = d; d = c; c = b; b = t;
84 u = rotlFixed(d*(2*d+1), 5);
85 t = rotlFixed(b*(2*b+1), 5);
86 c = rotrMod(c-sptr[1], t) ^ u;
87 a = rotrMod(a-sptr[0], u) ^ t;
88 }
89
90 sptr -= 2;
91 d -= sTable[1];
92 b -= sTable[0];
93
94 Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
95 }
96
97 NAMESPACE_END
98