1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
|
/* Bob Jenkins's cryptographic random number generators, ISAAC and ISAAC64.
Copyright (C) 1999-2006, 2009-2010 Free Software Foundation, Inc.
Copyright (C) 1997, 1998, 1999 Colin Plumb.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Written by Colin Plumb and Paul Eggert. */
/*
* --------------------------------------------------------------------
* We need a source of random numbers for some data.
* Cryptographically secure is desirable, but it's not life-or-death
* so I can be a little bit experimental in the choice of RNGs here.
*
* This generator is based somewhat on RC4, but has analysis
* <http://burtleburtle.net/bob/rand/isaacafa.html>
* pointing to it actually being better. I like it because it's nice
* and fast, and because the author did good work analyzing it.
* --------------------------------------------------------------------
*/
#include <config.h>
#include "rand-isaac.h"
#include <limits.h>
/* The minimum of two sizes A and B. */
static inline size_t
min (size_t a, size_t b)
{
return (a < b ? a : b);
}
/* A if 32-bit ISAAC, B if 64-bit. This is a macro, not an inline
function, to prevent undefined behavior if the unused argument
shifts by more than a word width. */
#define IF32(a, b) (ISAAC_BITS == 32 ? (a) : (b))
/* Discard bits outside the desired range. On typical machines, any
decent compiler should optimize this function call away to nothing.
But machines with pad bits in integers may need to do more work. */
static inline isaac_word
just (isaac_word a)
{
isaac_word desired_bits = ((isaac_word) 1 << 1 << (ISAAC_BITS - 1)) - 1;
return a & desired_bits;
}
/* The index operation. On typical machines whose words are exactly
the right size, this is optimized to a mask, an addition, and an
indirect load. Atypical machines need more work. */
static inline isaac_word
ind (isaac_word const *m, isaac_word x)
{
return (sizeof *m * CHAR_BIT == ISAAC_BITS
? (* (isaac_word *) ((char *) m
+ (x & ((ISAAC_WORDS - 1) * sizeof *m))))
: m[(x / (ISAAC_BITS / CHAR_BIT)) & (ISAAC_WORDS - 1)]);
}
/* Use and update *S to generate random data to fill RESULT. */
void
isaac_refill (struct isaac_state *s, isaac_word result[ISAAC_WORDS])
{
/* Caches of S->a and S->b. */
isaac_word a = s->a;
isaac_word b = s->b + (++s->c);
/* Pointers into state array and into result. */
isaac_word *m = s->m;
isaac_word *r = result;
enum { HALF = ISAAC_WORDS / 2 };
/* The central step. S->m is the whole state array, while M is a
pointer to the current word. OFF is the offset from M to the
word ISAAC_WORDS/2 words away in the SM array, i.e. +/-
ISAAC_WORDS/2. A and B are state variables, and R the result.
This updates A, B, M[I], and R[I]. */
#define ISAAC_STEP(i, off, mix) \
{ \
isaac_word x, y; \
a = (IF32 (a, 0) ^ (mix)) + m[off + (i)]; \
x = m[i]; \
m[i] = y = ind (s->m, x) + a + b; \
r[i] = b = just (ind (s->m, y >> ISAAC_WORDS_LOG) + x); \
}
do
{
ISAAC_STEP (0, HALF, IF32 ( a << 13, ~ (a ^ (a << 21))));
ISAAC_STEP (1, HALF, IF32 (just (a) >> 6, a ^ (just (a) >> 5)));
ISAAC_STEP (2, HALF, IF32 ( a << 2, a ^ ( a << 12)));
ISAAC_STEP (3, HALF, IF32 (just (a) >> 16, a ^ (just (a) >> 33)));
r += 4;
}
while ((m += 4) < s->m + HALF);
do
{
ISAAC_STEP (0, -HALF, IF32 ( a << 13, ~ (a ^ (a << 21))));
ISAAC_STEP (1, -HALF, IF32 (just (a) >> 6, a ^ (just (a) >> 5)));
ISAAC_STEP (2, -HALF, IF32 ( a << 2, a ^ ( a << 12)));
ISAAC_STEP (3, -HALF, IF32 (just (a) >> 16, a ^ (just (a) >> 33)));
r += 4;
}
while ((m += 4) < s->m + ISAAC_WORDS);
s->a = a;
s->b = b;
}
/*
* The basic seed-scrambling step for initialization, based on Bob
* Jenkins' 256-bit hash.
*/
#if ISAAC_BITS == 32
#define mix(a, b, c, d, e, f, g, h) \
{ \
a ^= b << 11; d += a; \
b += c; b ^= just (c) >> 2; e += b; \
c += d; c ^= d << 8; f += c; \
d += e; d ^= just (e) >> 16; g += d; \
e += f; e ^= f << 10; h += e; \
f += g; f ^= just (g) >> 4; a += f; \
g += h; g ^= h << 8; b += g; \
h += a; h ^= just (a) >> 9; c += h; \
a += b; \
}
#else
#define mix(a, b, c, d, e, f, g, h) \
{ \
a -= e; f ^= just (h) >> 9; h += a; \
b -= f; g ^= a << 9; a += b; \
c -= g; h ^= just (b) >> 23; b += c; \
d -= h; a ^= c << 15; c += d; \
e -= a; b ^= just (d) >> 14; d += e; \
f -= b; c ^= e << 20; e += f; \
g -= c; d ^= just (f) >> 17; f += g; \
h -= d; e ^= g << 14; g += h; \
}
#endif
/* The basic ISAAC initialization pass. */
#define ISAAC_MIX(s, a, b, c, d, e, f, g, h, seed) \
{ \
int i; \
\
for (i = 0; i < ISAAC_WORDS; i += 8) \
{ \
a += seed[i]; \
b += seed[i + 1]; \
c += seed[i + 2]; \
d += seed[i + 3]; \
e += seed[i + 4]; \
f += seed[i + 5]; \
g += seed[i + 6]; \
h += seed[i + 7]; \
mix (a, b, c, d, e, f, g, h); \
s->m[i] = a; \
s->m[i + 1] = b; \
s->m[i + 2] = c; \
s->m[i + 3] = d; \
s->m[i + 4] = e; \
s->m[i + 5] = f; \
s->m[i + 6] = g; \
s->m[i + 7] = h; \
} \
}
#if 0 /* Provided for reference only; not used in this code */
/*
* Initialize the ISAAC RNG with the given seed material.
* Its size MUST be a multiple of ISAAC_BYTES, and may be
* stored in the s->m array.
*
* This is a generalization of the original ISAAC initialization code
* to support larger seed sizes. For seed sizes of 0 and ISAAC_BYTES,
* it is identical.
*/
static void
isaac_init (struct isaac_state *s, isaac_word const *seed, size_t seedsize)
{
isaac_word a, b, c, d, e, f, g, h;
a = b = c = d = e = f = g = h = /* the golden ratio */
IF32 (UINT32_C (0x9e3779b9), UINT64_C (0x9e3779b97f4a7c13));
for (int i = 0; i < 4; i++) /* scramble it */
mix (a, b, c, d, e, f, g, h);
s->a = s->b = s->c = 0;
if (seedsize)
{
/* First pass (as in reference ISAAC code) */
ISAAC_MIX (s, a, b, c, d, e, f, g, h, seed);
/* Second and subsequent passes (extension to ISAAC) */
while (seedsize -= ISAAC_BYTES)
{
seed += ISAAC_WORDS;
for (i = 0; i < ISAAC_WORDS; i++)
s->m[i] += seed[i];
ISAAC_MIX (s, a, b, c, d, e, f, g, h, s->m);
}
}
else
{
/* The no seed case (as in reference ISAAC code) */
for (i = 0; i < ISAAC_WORDS; i++)
s->m[i] = 0;
}
/* Final pass */
ISAAC_MIX (s, a, b, c, d, e, f, g, h, s->m);
}
#endif
/* Initialize *S to a somewhat-random value, derived from a seed
stored in S->m. */
void
isaac_seed (struct isaac_state *s)
{
isaac_word a = IF32 (UINT32_C (0x1367df5a), UINT64_C (0x647c4677a2884b7c));
isaac_word b = IF32 (UINT32_C (0x95d90059), UINT64_C (0xb9f8b322c73ac862));
isaac_word c = IF32 (UINT32_C (0xc3163e4b), UINT64_C (0x8c0ea5053d4712a0));
isaac_word d = IF32 (UINT32_C (0x0f421ad8), UINT64_C (0xb29b2e824a595524));
isaac_word e = IF32 (UINT32_C (0xd92a4a78), UINT64_C (0x82f053db8355e0ce));
isaac_word f = IF32 (UINT32_C (0xa51a3c49), UINT64_C (0x48fe4a0fa5a09315));
isaac_word g = IF32 (UINT32_C (0xc4efea1b), UINT64_C (0xae985bf2cbfc89ed));
isaac_word h = IF32 (UINT32_C (0x30609119), UINT64_C (0x98f5704f6c44c0ab));
#if 0
/* The initialization of a through h is a precomputed form of: */
a = b = c = d = e = f = g = h = /* the golden ratio */
IF32 (UINT32_C (0x9e3779b9), UINT64_C (0x9e3779b97f4a7c13));
for (int i = 0; i < 4; i++) /* scramble it */
mix (a, b, c, d, e, f, g, h);
#endif
/* Mix S->m so that every part of the seed affects every part of the
state. */
ISAAC_MIX (s, a, b, c, d, e, f, g, h, s->m);
ISAAC_MIX (s, a, b, c, d, e, f, g, h, s->m);
s->a = s->b = s->c = 0;
}
|
