Crypto++  5.6.5
Free C++ class library of cryptographic schemes
twofish.cpp
1 // twofish.cpp - modified by Wei Dai from Matthew Skala's twofish.c
2 // The original code and all modifications are in the public domain.
3 
4 #include "pch.h"
5 #include "twofish.h"
6 #include "secblock.h"
7 #include "misc.h"
8 
9 NAMESPACE_BEGIN(CryptoPP)
10 
11 // compute (c * x^4) mod (x^4 + (a + 1/a) * x^3 + a * x^2 + (a + 1/a) * x + 1)
12 // over GF(256)
13 static inline unsigned int Mod(unsigned int c)
14 {
15  static const unsigned int modulus = 0x14d;
16  unsigned int c2 = (c<<1) ^ ((c & 0x80) ? modulus : 0);
17  unsigned int c1 = c2 ^ (c>>1) ^ ((c & 1) ? (modulus>>1) : 0);
18  return c | (c1 << 8) | (c2 << 16) | (c1 << 24);
19 }
20 
21 // compute RS(12,8) code with the above polynomial as generator
22 // this is equivalent to multiplying by the RS matrix
23 static word32 ReedSolomon(word32 high, word32 low)
24 {
25  for (unsigned int i=0; i<8; i++)
26  {
27  high = Mod(high>>24) ^ (high<<8) ^ (low>>24);
28  low <<= 8;
29  }
30  return high;
31 }
32 
33 inline word32 Twofish::Base::h0(word32 x, const word32 *key, unsigned int kLen)
34 {
35  x = x | (x<<8) | (x<<16) | (x<<24);
36  switch(kLen)
37  {
38 #define Q(a, b, c, d, t) q[a][GETBYTE(t,0)] ^ (q[b][GETBYTE(t,1)] << 8) ^ (q[c][GETBYTE(t,2)] << 16) ^ (q[d][GETBYTE(t,3)] << 24)
39  case 4: x = Q(1, 0, 0, 1, x) ^ key[6];
40  // fall through
41  case 3: x = Q(1, 1, 0, 0, x) ^ key[4];
42  // fall through
43  case 2: x = Q(0, 1, 0, 1, x) ^ key[2];
44  x = Q(0, 0, 1, 1, x) ^ key[0];
45  }
46  return x;
47 }
48 
49 inline word32 Twofish::Base::h(word32 x, const word32 *key, unsigned int kLen)
50 {
51  x = h0(x, key, kLen);
52  return mds[0][GETBYTE(x,0)] ^ mds[1][GETBYTE(x,1)] ^ mds[2][GETBYTE(x,2)] ^ mds[3][GETBYTE(x,3)];
53 }
54 
55 void Twofish::Base::UncheckedSetKey(const byte *userKey, unsigned int keylength, const NameValuePairs &)
56 {
57  AssertValidKeyLength(keylength);
58 
59  unsigned int len = (keylength <= 16 ? 2 : (keylength <= 24 ? 3 : 4));
60  SecBlock<word32> key(len*2);
61  GetUserKey(LITTLE_ENDIAN_ORDER, key.begin(), len*2, userKey, keylength);
62 
63  unsigned int i;
64  for (i=0; i<40; i+=2)
65  {
66  word32 a = h(i, key, len);
67  word32 b = rotlConstant<8>(h(i + 1, key + 1, len));
68  m_k[i] = a+b;
69  m_k[i + 1] = rotlConstant<9>(a + 2 * b);
70  }
71 
72  SecBlock<word32> svec(2*len);
73  for (i=0; i<len; i++)
74  svec[2*(len-i-1)] = ReedSolomon(key[2*i+1], key[2*i]);
75  for (i=0; i<256; i++)
76  {
77  word32 t = h0(i, svec, len);
78  m_s[0*256+i] = mds[0][GETBYTE(t, 0)];
79  m_s[1*256+i] = mds[1][GETBYTE(t, 1)];
80  m_s[2*256+i] = mds[2][GETBYTE(t, 2)];
81  m_s[3*256+i] = mds[3][GETBYTE(t, 3)];
82  }
83 }
84 
85 #define G1(x) (m_s[0*256+GETBYTE(x,0)] ^ m_s[1*256+GETBYTE(x,1)] ^ m_s[2*256+GETBYTE(x,2)] ^ m_s[3*256+GETBYTE(x,3)])
86 #define G2(x) (m_s[0*256+GETBYTE(x,3)] ^ m_s[1*256+GETBYTE(x,0)] ^ m_s[2*256+GETBYTE(x,1)] ^ m_s[3*256+GETBYTE(x,2)])
87 
88 #define ENCROUND(n, a, b, c, d) \
89  x = G1 (a); y = G2 (b); \
90  x += y; y += x + k[2 * (n) + 1]; \
91  (c) ^= x + k[2 * (n)]; \
92  (c) = rotrConstant<1>(c); \
93  (d) = rotlConstant<1>(d) ^ y
94 
95 #define ENCCYCLE(n) \
96  ENCROUND (2 * (n), a, b, c, d); \
97  ENCROUND (2 * (n) + 1, c, d, a, b)
98 
99 #define DECROUND(n, a, b, c, d) \
100  x = G1 (a); y = G2 (b); \
101  x += y; y += x; \
102  (d) ^= y + k[2 * (n) + 1]; \
103  (d) = rotrConstant<1>(d); \
104  (c) = rotlConstant<1>(c); \
105  (c) ^= (x + k[2 * (n)])
106 
107 #define DECCYCLE(n) \
108  DECROUND (2 * (n) + 1, c, d, a, b); \
109  DECROUND (2 * (n), a, b, c, d)
110 
112 
113 void Twofish::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
114 {
115  word32 x, y, a, b, c, d;
116 
117  Block::Get(inBlock)(a)(b)(c)(d);
118 
119  a ^= m_k[0];
120  b ^= m_k[1];
121  c ^= m_k[2];
122  d ^= m_k[3];
123 
124  const word32 *k = m_k+8;
125  ENCCYCLE (0);
126  ENCCYCLE (1);
127  ENCCYCLE (2);
128  ENCCYCLE (3);
129  ENCCYCLE (4);
130  ENCCYCLE (5);
131  ENCCYCLE (6);
132  ENCCYCLE (7);
133 
134  c ^= m_k[4];
135  d ^= m_k[5];
136  a ^= m_k[6];
137  b ^= m_k[7];
138 
139  Block::Put(xorBlock, outBlock)(c)(d)(a)(b);
140 }
141 
142 void Twofish::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
143 {
144  word32 x, y, a, b, c, d;
145 
146  Block::Get(inBlock)(c)(d)(a)(b);
147 
148  c ^= m_k[4];
149  d ^= m_k[5];
150  a ^= m_k[6];
151  b ^= m_k[7];
152 
153  const word32 *k = m_k+8;
154  DECCYCLE (7);
155  DECCYCLE (6);
156  DECCYCLE (5);
157  DECCYCLE (4);
158  DECCYCLE (3);
159  DECCYCLE (2);
160  DECCYCLE (1);
161  DECCYCLE (0);
162 
163  a ^= m_k[0];
164  b ^= m_k[1];
165  c ^= m_k[2];
166  d ^= m_k[3];
167 
168  Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
169 }
170 
171 NAMESPACE_END
Utility functions for the Crypto++ library.
Access a block of memory.
Definition: misc.h:2398
byte order is little-endian
Definition: cryptlib.h:143
Classes for the Twofish block cipher.
Classes and functions for secure memory allocations.
Access a block of memory.
Definition: misc.h:2361
Crypto++ library namespace.
Interface for retrieving values given their names.
Definition: cryptlib.h:291