Crypto++  8.8
Free C++ class library of cryptographic schemes
rc6.cpp
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 
9 NAMESPACE_BEGIN(CryptoPP)
10 
11 void RC6::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs &params)
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()] = rotlConstant<3>((sTable[h % sTable.size()] + a + b));
37  b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
38  }
39 }
40 
42 
43 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 = rotlConstant<5>(b*(2*b+1));
56  u = rotlConstant<5>(d*(2*d+1));
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 
69 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 = rotlConstant<5>(d*(2 * d + 1));
85  t = rotlConstant<5>(b*(2 * b + 1));
86  c = rotrMod(c-sptr[1], t) ^ u;
87  a = rotrMod(a-sptr[0], u) ^ t;
88  }
89 
90  d -= sTable[1];
91  b -= sTable[0];
92 
93  Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
94 }
95 
96 NAMESPACE_END
Interface for retrieving values given their names.
Definition: cryptlib.h:327
Access a block of memory.
Definition: misc.h:3016
@ LITTLE_ENDIAN_ORDER
byte order is little-endian
Definition: cryptlib.h:150
Utility functions for the Crypto++ library.
void GetUserKey(ByteOrder order, T *out, size_t outlen, const byte *in, size_t inlen)
Copy bytes in a buffer to an array of elements in big-endian order.
Definition: misc.h:2500
T rotlMod(T x, unsigned int y)
Performs a left rotate.
Definition: misc.h:1894
T rotrMod(T x, unsigned int y)
Performs a right rotate.
Definition: misc.h:1910
const T & STDMAX(const T &a, const T &b)
Replacement function for std::max.
Definition: misc.h:668
Crypto++ library namespace.
Precompiled header file.
Classes for the RC6 block cipher.
Classes and functions for secure memory allocations.
Access a block of memory.
Definition: misc.h:3053