Crypto++
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 "misc.h"
7 
8 NAMESPACE_BEGIN(CryptoPP)
9 
10 // compute (c * x^4) mod (x^4 + (a + 1/a) * x^3 + a * x^2 + (a + 1/a) * x + 1)
11 // over GF(256)
12 static inline unsigned int Mod(unsigned int c)
13 {
14  static const unsigned int modulus = 0x14d;
15  unsigned int c2 = (c<<1) ^ ((c & 0x80) ? modulus : 0);
16  unsigned int c1 = c2 ^ (c>>1) ^ ((c & 1) ? (modulus>>1) : 0);
17  return c | (c1 << 8) | (c2 << 16) | (c1 << 24);
18 }
19 
20 // compute RS(12,8) code with the above polynomial as generator
21 // this is equivalent to multiplying by the RS matrix
22 static word32 ReedSolomon(word32 high, word32 low)
23 {
24  for (unsigned int i=0; i<8; i++)
25  {
26  high = Mod(high>>24) ^ (high<<8) ^ (low>>24);
27  low <<= 8;
28  }
29  return high;
30 }
31 
32 inline word32 Twofish::Base::h0(word32 x, const word32 *key, unsigned int kLen)
33 {
34  x = x | (x<<8) | (x<<16) | (x<<24);
35  switch(kLen)
36  {
37 #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)
38  case 4: x = Q(1, 0, 0, 1, x) ^ key[6];
39  case 3: x = Q(1, 1, 0, 0, x) ^ key[4];
40  case 2: x = Q(0, 1, 0, 1, x) ^ key[2];
41  x = Q(0, 0, 1, 1, x) ^ key[0];
42  }
43  return x;
44 }
45 
46 inline word32 Twofish::Base::h(word32 x, const word32 *key, unsigned int kLen)
47 {
48  x = h0(x, key, kLen);
49  return mds[0][GETBYTE(x,0)] ^ mds[1][GETBYTE(x,1)] ^ mds[2][GETBYTE(x,2)] ^ mds[3][GETBYTE(x,3)];
50 }
51 
52 void Twofish::Base::UncheckedSetKey(const byte *userKey, unsigned int keylength, const NameValuePairs &)
53 {
54  AssertValidKeyLength(keylength);
55 
56  unsigned int len = (keylength <= 16 ? 2 : (keylength <= 24 ? 3 : 4));
57  SecBlock<word32> key(len*2);
58  GetUserKey(LITTLE_ENDIAN_ORDER, key.begin(), len*2, userKey, keylength);
59 
60  unsigned int i;
61  for (i=0; i<40; i+=2)
62  {
63  word32 a = h(i, key, len);
64  word32 b = rotlFixed(h(i+1, key+1, len), 8);
65  m_k[i] = a+b;
66  m_k[i+1] = rotlFixed(a+2*b, 9);
67  }
68 
69  SecBlock<word32> svec(2*len);
70  for (i=0; i<len; i++)
71  svec[2*(len-i-1)] = ReedSolomon(key[2*i+1], key[2*i]);
72  for (i=0; i<256; i++)
73  {
74  word32 t = h0(i, svec, len);
75  m_s[0*256+i] = mds[0][GETBYTE(t, 0)];
76  m_s[1*256+i] = mds[1][GETBYTE(t, 1)];
77  m_s[2*256+i] = mds[2][GETBYTE(t, 2)];
78  m_s[3*256+i] = mds[3][GETBYTE(t, 3)];
79  }
80 }
81 
82 #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)])
83 #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)])
84 
85 #define ENCROUND(n, a, b, c, d) \
86  x = G1 (a); y = G2 (b); \
87  x += y; y += x + k[2 * (n) + 1]; \
88  (c) ^= x + k[2 * (n)]; \
89  (c) = rotrFixed(c, 1); \
90  (d) = rotlFixed(d, 1) ^ y
91 
92 #define ENCCYCLE(n) \
93  ENCROUND (2 * (n), a, b, c, d); \
94  ENCROUND (2 * (n) + 1, c, d, a, b)
95 
96 #define DECROUND(n, a, b, c, d) \
97  x = G1 (a); y = G2 (b); \
98  x += y; y += x; \
99  (d) ^= y + k[2 * (n) + 1]; \
100  (d) = rotrFixed(d, 1); \
101  (c) = rotlFixed(c, 1); \
102  (c) ^= (x + k[2 * (n)])
103 
104 #define DECCYCLE(n) \
105  DECROUND (2 * (n) + 1, c, d, a, b); \
106  DECROUND (2 * (n), a, b, c, d)
107 
109 
110 void Twofish::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
111 {
112  word32 x, y, a, b, c, d;
113 
114  Block::Get(inBlock)(a)(b)(c)(d);
115 
116  a ^= m_k[0];
117  b ^= m_k[1];
118  c ^= m_k[2];
119  d ^= m_k[3];
120 
121  const word32 *k = m_k+8;
122  ENCCYCLE (0);
123  ENCCYCLE (1);
124  ENCCYCLE (2);
125  ENCCYCLE (3);
126  ENCCYCLE (4);
127  ENCCYCLE (5);
128  ENCCYCLE (6);
129  ENCCYCLE (7);
130 
131  c ^= m_k[4];
132  d ^= m_k[5];
133  a ^= m_k[6];
134  b ^= m_k[7];
135 
136  Block::Put(xorBlock, outBlock)(c)(d)(a)(b);
137 }
138 
139 void Twofish::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
140 {
141  word32 x, y, a, b, c, d;
142 
143  Block::Get(inBlock)(c)(d)(a)(b);
144 
145  c ^= m_k[4];
146  d ^= m_k[5];
147  a ^= m_k[6];
148  b ^= m_k[7];
149 
150  const word32 *k = m_k+8;
151  DECCYCLE (7);
152  DECCYCLE (6);
153  DECCYCLE (5);
154  DECCYCLE (4);
155  DECCYCLE (3);
156  DECCYCLE (2);
157  DECCYCLE (1);
158  DECCYCLE (0);
159 
160  a ^= m_k[0];
161  b ^= m_k[1];
162  c ^= m_k[2];
163  d ^= m_k[3];
164 
165  Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
166 }
167 
168 NAMESPACE_END