From msuinfo!agate!howland.reston.ans.net!cs.utexas.edu!not-for-mail Fri Mar 11 23:00:03 1994
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From: boucher@csl.sri.com (Peter K. Boucher)
Newsgroups: sci.crypt
Subject: Modified Jenkins PRNG source
Date: 11 Mar 1994 19:24:03 -0600
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/* --------------------------------------------------------------------------
  "Random.  Fast.  Easy to code.  Probably unbreakable.  This rng was
   designed for encryption and simulation.  It is now unpatentable and in
   the worldwide public domain.  Please use it!"

            - Bob Jenkins
            rjenkins@us.oracle.com

  "Modified to take 128-bits of seed.  Buffer size increased to 1024.
   Function rand32_mod() added."

            - Peter K. Boucher
            boucher@csl.sri.com
-------------------------------------------------------------------------- */
/* WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING

The following 3 defines are related.  If you change one, change all three.

   WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING */
#define BSIZE 1024 /* #longs in secret state (must be power of 2) */
#define BMASK 1023 /* BSIZE - 1 */
#define BSHFT 22   /* 32 - #bits in BMASK */

static unsigned long num_rands = 0;
static unsigned long *rand_ptr;
static unsigned long m[BSIZE], r[BSIZE];
static unsigned long A, B;
static unsigned long *me = &(m[BSIZE]);

static unsigned long 
refresh_rng_state()
{
  register unsigned long a,b,x,y,*mi,*ri;

  a = A;  b = B;
  mi = m;
  ri = r; 
  while (mi<me) {
    x       = *mi;
    y       = m[x>>BSHFT];                    /* one of m[0]..m[BMASK] */
    a       = ((a<<27)^(a>>5));                       /* barrelshift a */
    a       = a+y;                                      /* accumulator */
    *(mi++) = a+b;                                    /* secret memory */
    *(ri++) = b+y;                             /* result given to user */
    b       = x;
  }
  B = b;  A = a;

  num_rands = BMASK;
  rand_ptr = &(r[1]);
  return( r[0] );
}

unsigned long
rand32()
{
    return( (num_rands--) ? *(rand_ptr++) : refresh_rng_state() );
}

unsigned long
rand32_mod(max)
unsigned long max;
{
   register unsigned long rdm_val;
   register unsigned long limit = ((0xFFFFFFFFL/max)*max);

   if (max < 2L) return(0L);

   do {
       rdm_val = ( (num_rands--) ? *(rand_ptr++) : refresh_rng_state() );
   } while (rdm_val >= limit);

   return(rdm_val % max);
}

void
srand128(seed1,seed2,seed3,seed4)
unsigned long seed1,seed2,seed3,seed4;
{
#define LC1(X) (X * 66049 + 3907864577)
#define LC2(X) (X * 69069)

    register int i,j;
    register unsigned long rdm_val=0L;
    register unsigned long x=seed1;
    register unsigned long y=seed2;

    while ((x&1) == 0) {
  x = LC1(x);
    }
    for (i=BSIZE; i--;) {
        for (j=32;j--;) {
      if (y == 0) y = LC1(x);
      y ^= (y >> 15);
      y ^= (y << 17);
      rdm_val = (rdm_val>>1) | (0x80000000 & ((x=LC2(x))+y));
        }
  m[i] = rdm_val;
    }
    for (i=32;i--;) {
  if (y == 0) y = LC1(x);
  y ^= (y >> 15);
  y ^= (y << 17);
  rdm_val = (rdm_val>>1) | (0x80000000 & ((x=LC2(x))+y));
    }
    A = rdm_val;
    for (i=32;i--;) {
  if (y == 0) y = LC1(x);
  y ^= (y >> 15);
  y ^= (y << 17);
  rdm_val = (rdm_val>>1) | (0x80000000 & ((x=LC2(x))+y));
    }

    x=seed3;
    y=seed4;
    while ((x&1) == 0) {
  x = LC1(x);
    }
    for (i=0; i<BSIZE; i++) {
        for (j=32;j--;) {
      if (y == 0) y = LC1(x);
      y ^= (y >> 15);
      y ^= (y << 17);
      rdm_val = (rdm_val<<1) | (((x=LC2(x))+y) >> 31);
        }
  m[i] ^= rdm_val;
    }
    for (i=32;i--;) {
  if (y == 0) y = LC1(x);
  y ^= (y >> 15);
  y ^= (y << 17);
  rdm_val = (rdm_val<<1) | (((x=LC2(x))+y) >> 31);
    }
    A ^= rdm_val;
    for (i=32;i--;) {
  if (y == 0) y = LC1(x);
  y ^= (y >> 15);
  y ^= (y << 17);
  rdm_val = (rdm_val<<1) | (((x=LC2(x))+y) >> 31);
    }
    B ^= rdm_val;

    for (i=100; i--;) {
  (void)refresh_rng_state();          /* mix it up some */
    }
    for (i=1+(m[(seed1^seed2^seed3^seed4)&BMASK]&BMASK); i--;) {
  (void)rand32();
    }
}