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
8NAMESPACE_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)
12static 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
22static 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
32inline 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
46inline 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
52void 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][i] = mds[0][GETBYTE(t, 0)];
76		m_s[1][i] = mds[1][GETBYTE(t, 1)];
77		m_s[2][i] = mds[2][GETBYTE(t, 2)];
78		m_s[3][i] = mds[3][GETBYTE(t, 3)];
79	}
80}
81
82#define G1(x) (m_s[0][GETBYTE(x,0)] ^ m_s[1][GETBYTE(x,1)] ^ m_s[2][GETBYTE(x,2)] ^ m_s[3][GETBYTE(x,3)])
83#define G2(x) (m_s[0][GETBYTE(x,3)] ^ m_s[1][GETBYTE(x,0)] ^ m_s[2][GETBYTE(x,1)] ^ m_s[3][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
108typedef BlockGetAndPut<word32, LittleEndian> Block;
109
110void 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
139void 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
168NAMESPACE_END
169