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DEFINITIONS
This source file includes following definitions.
- isaac_refill
- isaac_mix
- isaac_init
- isaac_seed_start
- isaac_seed_data
- isaac_seed_finish
- isaac_seed
/* Bob Jenkins's cryptographic random number generator, ISAAC.
Copyright (C) 1999-2006 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 2, 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, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
Written by Colin Plumb. */
/*
* --------------------------------------------------------------------
* 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 <string.h>
#include <unistd.h>
#include "gethrxtime.h"
/* This index operation is more efficient on many processors */
#define ind(mm, x) \
(* (uint32_t *) ((char *) (mm) \
+ ((x) & (ISAAC_WORDS - 1) * sizeof (uint32_t))))
/*
* The central step. This uses two temporaries, x and y. mm 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 mm array,
* i.e. +/- ISAAC_WORDS/2.
*/
#define isaac_step(mix, a, b, mm, m, off, r) \
( \
a = ((a) ^ (mix)) + (m)[off], \
x = *(m), \
*(m) = y = ind (mm, x) + (a) + (b), \
*(r) = b = ind (mm, (y) >> ISAAC_LOG) + x \
)
/* Use and update *S to generate random data to fill R. */
void
isaac_refill (struct isaac_state *s, uint32_t r[ISAAC_WORDS])
{
uint32_t a, b; /* Caches of a and b */
uint32_t x, y; /* Temps needed by isaac_step macro */
uint32_t *m = s->mm; /* Pointer into state array */
a = s->a;
b = s->b + (++s->c);
do
{
isaac_step (a << 13, a, b, s->mm, m, ISAAC_WORDS / 2, r);
isaac_step (a >> 6, a, b, s->mm, m + 1, ISAAC_WORDS / 2, r + 1);
isaac_step (a << 2, a, b, s->mm, m + 2, ISAAC_WORDS / 2, r + 2);
isaac_step (a >> 16, a, b, s->mm, m + 3, ISAAC_WORDS / 2, r + 3);
r += 4;
}
while ((m += 4) < s->mm + ISAAC_WORDS / 2);
do
{
isaac_step (a << 13, a, b, s->mm, m, -ISAAC_WORDS / 2, r);
isaac_step (a >> 6, a, b, s->mm, m + 1, -ISAAC_WORDS / 2, r + 1);
isaac_step (a << 2, a, b, s->mm, m + 2, -ISAAC_WORDS / 2, r + 2);
isaac_step (a >> 16, a, b, s->mm, m + 3, -ISAAC_WORDS / 2, r + 3);
r += 4;
}
while ((m += 4) < s->mm + ISAAC_WORDS);
s->a = a;
s->b = b;
}
/*
* The basic seed-scrambling step for initialization, based on Bob
* Jenkins' 256-bit hash.
*/
#define mix(a,b,c,d,e,f,g,h) \
( a ^= b << 11, d += a, \
b += c, b ^= c >> 2, e += b, \
c += d, c ^= d << 8, f += c, \
d += e, d ^= e >> 16, g += d, \
e += f, e ^= f << 10, h += e, \
f += g, f ^= g >> 4, a += f, \
g += h, g ^= h << 8, b += g, \
h += a, h ^= a >> 9, c += h, \
a += b )
/* The basic ISAAC initialization pass. */
static void
isaac_mix (struct isaac_state *s, uint32_t const seed[/* ISAAC_WORDS */])
{
int i;
uint32_t a = s->iv[0];
uint32_t b = s->iv[1];
uint32_t c = s->iv[2];
uint32_t d = s->iv[3];
uint32_t e = s->iv[4];
uint32_t f = s->iv[5];
uint32_t g = s->iv[6];
uint32_t h = s->iv[7];
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->mm[i] = a;
s->mm[i + 1] = b;
s->mm[i + 2] = c;
s->mm[i + 3] = d;
s->mm[i + 4] = e;
s->mm[i + 5] = f;
s->mm[i + 6] = g;
s->mm[i + 7] = h;
}
s->iv[0] = a;
s->iv[1] = b;
s->iv[2] = c;
s->iv[3] = d;
s->iv[4] = e;
s->iv[5] = f;
s->iv[6] = g;
s->iv[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->mm 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, uint32_t const *seed, size_t seedsize)
{
static uint32_t const iv[8] =
{
0x1367df5a, 0x95d90059, 0xc3163e4b, 0x0f421ad8,
0xd92a4a78, 0xa51a3c49, 0xc4efea1b, 0x30609119};
int i;
# if 0
/* The initialization of iv is a precomputed form of: */
for (i = 0; i < 7; i++)
iv[i] = 0x9e3779b9; /* the golden ratio */
for (i = 0; i < 4; ++i) /* scramble it */
mix (iv[0], iv[1], iv[2], iv[3], iv[4], iv[5], iv[6], iv[7]);
# endif
s->a = s->b = s->c = 0;
for (i = 0; i < 8; i++)
s->iv[i] = iv[i];
if (seedsize)
{
/* First pass (as in reference ISAAC code) */
isaac_mix (s, seed);
/* Second and subsequent passes (extension to ISAAC) */
while (seedsize -= ISAAC_BYTES)
{
seed += ISAAC_WORDS;
for (i = 0; i < ISAAC_WORDS; i++)
s->mm[i] += seed[i];
isaac_mix (s, s->mm);
}
}
else
{
/* The no seed case (as in reference ISAAC code) */
for (i = 0; i < ISAAC_WORDS; i++)
s->mm[i] = 0;
}
/* Final pass */
isaac_mix (s, s->mm);
}
#endif
/* Initialize *S to a somewhat-random value. */
static void
isaac_seed_start (struct isaac_state *s)
{
static uint32_t const iv[8] =
{
0x1367df5a, 0x95d90059, 0xc3163e4b, 0x0f421ad8,
0xd92a4a78, 0xa51a3c49, 0xc4efea1b, 0x30609119
};
#if 0
/* The initialization of iv is a precomputed form of: */
int i;
for (i = 0; i < 7; i++)
iv[i] = 0x9e3779b9; /* the golden ratio */
for (i = 0; i < 4; ++i) /* scramble it */
mix (iv[0], iv[1], iv[2], iv[3], iv[4], iv[5], iv[6], iv[7]);
#endif
memset (s->mm, 0, sizeof s->mm);
memcpy (s->iv, iv, sizeof s->iv);
/* s->c gets used for a data pointer during the seeding phase */
s->a = s->b = s->c = 0;
}
/* Add a buffer of seed material. */
static void
isaac_seed_data (struct isaac_state *s, void const *buffer, size_t size)
{
unsigned char const *buf = buffer;
unsigned char *p;
size_t avail;
size_t i;
avail = sizeof s->mm - s->c; /* s->c is used as a write pointer */
/* Do any full buffers that are necessary */
while (size > avail)
{
p = (unsigned char *) s->mm + s->c;
for (i = 0; i < avail; i++)
p[i] ^= buf[i];
buf += avail;
size -= avail;
isaac_mix (s, s->mm);
s->c = 0;
avail = sizeof s->mm;
}
/* And the final partial block */
p = (unsigned char *) s->mm + s->c;
for (i = 0; i < size; i++)
p[i] ^= buf[i];
s->c = size;
}
/* End of seeding phase; get everything ready to produce output. */
static void
isaac_seed_finish (struct isaac_state *s)
{
isaac_mix (s, s->mm);
isaac_mix (s, s->mm);
/* Now reinitialize c to start things off right */
s->c = 0;
}
#define ISAAC_SEED(s,x) isaac_seed_data (s, &(x), sizeof (x))
/* Initialize *S to a somewhat-random value; this starts seeding,
seeds with somewhat-random data, and finishes seeding. */
void
isaac_seed (struct isaac_state *s)
{
isaac_seed_start (s);
{ pid_t t = getpid (); ISAAC_SEED (s, t); }
{ pid_t t = getppid (); ISAAC_SEED (s, t); }
{ uid_t t = getuid (); ISAAC_SEED (s, t); }
{ gid_t t = getgid (); ISAAC_SEED (s, t); }
{
xtime_t t = gethrxtime ();
ISAAC_SEED (s, t);
}
isaac_seed_finish (s);
}