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MD5_PRNG.c
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MD5_PRNG.c
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#include <fcntl.h>
/*
* After becoming frustrated with the lack of a standalone, portable,
* decent random number generator, I decided to make one based on a
* cryptographic one-way hash function. I chose MD5 since it is fast
* and free source was readily available. More cryptographically
* secure hash functions are available (e.g. SHA-1), but for the
* purposes of a rand/random/erand48 replacement, MD5 should be more
* than sufficient.
*
* MD5 takes an arbitrary amount of input and yields a 16 byte hash.
* This RNG continually MD5's a 16 byte digest, and uses the bottom N
* bits as the random number yielded, where N is just large enough to
* include the largest random number desired.
*
* To yield a random number between 0 and r:
*
* create mask which has enough bits to include all of r
* (for example, if r is 100, mask would be 0x7F)
*
* do {
* digest = MD5(digest)
* number = digest & mask
* } while (number > r)
*
* The digest should be loaded and saved to a disk file between
* invocations of a program using the RNG.
*
* Random functions appear after the included MD5 code.
*
* Send comments to: skrenta@pbm.com (Rich Skrenta)
*/
/*****************************************************************/
/*
* This code implements the MD5 message-digest algorithm.
* The algorithm is due to Ron Rivest. This code was
* written by Colin Plumb in 1993, no copyright is claimed.
* This code is in the public domain; do with it what you wish.
*
* Equivalent code is available from RSA Data Security, Inc.
* This code has been tested against that, and is equivalent,
* except that you don't need to include two pages of legalese
* with every copy.
*
* To compute the message digest of a chunk of bytes, declare an
* MD5Context structure, pass it to MD5Init, call MD5Update as
* needed on buffers full of bytes, and then call MD5Final, which
* will fill a supplied 16-byte array with the digest.
*/
typedef ULONG word32;
typedef UBYTE byte;
struct xMD5Context {
ULONG buf[4];
ULONG bytes[2];
ULONG in[16];
};
void xMD5Init(struct xMD5Context *context);
void xMD5Update(struct xMD5Context *context, UBYTE const *buf, int len);
void xMD5Final(byte digest[16], struct xMD5Context *context);
void xMD5Transform(ULONG buf[4], ULONG const in[16]);
/*
* Shuffle the bytes into little-endian order within words, as per the
* MD5 spec. Note: this code works regardless of the byte order.
*/
void
byteSwap(ULONG *buf, unsigned words)
{
UBYTE *p = (byte *)buf;
do {
*buf++ = (ULONG)((unsigned)p[3] << 8 | p[2]) << 16 |
((unsigned)p[1] << 8 | p[0]);
p += 4;
} while (--words);
}
/*
* Start MD5 accumulation. Set bit count to 0 and buffer to mysterious
* initialization constants.
*/
void
xMD5Init(struct xMD5Context *ctx)
{
ctx->buf[0] = 0x67452301;
ctx->buf[1] = 0xefcdab89;
ctx->buf[2] = 0x98badcfe;
ctx->buf[3] = 0x10325476;
ctx->bytes[0] = 0;
ctx->bytes[1] = 0;
}
/*
* Update context to reflect the concatenation of another buffer full
* of bytes.
*/
void
xMD5Update(struct xMD5Context *ctx, UBYTE const *buf, int len)
{
ULONG t;
/* Update byte count */
t = ctx->bytes[0];
if ((ctx->bytes[0] = t + len) < t)
ctx->bytes[1]++; /* Carry from low to high */
t = 64 - (t & 0x3f); /* Space available in ctx->in (at least 1) */
if ((unsigned)t > len) {
bcopy(buf, (byte *)ctx->in + 64 - (unsigned)t, len);
return;
}
/* First chunk is an odd size */
bcopy(buf,(byte *)ctx->in + 64 - (unsigned)t, (unsigned)t);
byteSwap(ctx->in, 16);
xMD5Transform(ctx->buf, ctx->in);
buf += (unsigned)t;
len -= (unsigned)t;
/* Process data in 64-byte chunks */
while (len >= 64) {
bcopy(buf, ctx->in, 64);
byteSwap(ctx->in, 16);
xMD5Transform(ctx->buf, ctx->in);
buf += 64;
len -= 64;
}
/* Handle any remaining bytes of data. */
bcopy(buf, ctx->in, len);
}
/*
* Final wrapup - pad to 64-byte boundary with the bit pattern
* 1 0* (64-bit count of bits processed, MSB-first)
*/
void
xMD5Final(byte digest[16], struct xMD5Context *ctx)
{
int count = (int)(ctx->bytes[0] & 0x3f); /* Bytes in ctx->in */
UBYTE *p = (byte *)ctx->in + count; /* First unused byte */
/* Set the first char of padding to 0x80. There is always room. */
*p++ = 0x80;
/* Bytes of padding needed to make 56 bytes (-8..55) */
count = 56 - 1 - count;
if (count < 0) { /* Padding forces an extra block */
bzero(p, count+8);
byteSwap(ctx->in, 16);
xMD5Transform(ctx->buf, ctx->in);
p = (byte *)ctx->in;
count = 56;
}
bzero(p, count+8);
byteSwap(ctx->in, 14);
/* Append length in bits and transform */
ctx->in[14] = ctx->bytes[0] << 3;
ctx->in[15] = ctx->bytes[1] << 3 | ctx->bytes[0] >> 29;
xMD5Transform(ctx->buf, ctx->in);
byteSwap(ctx->buf, 4);
bcopy(ctx->buf, digest, 16);
bzero(ctx,sizeof(ctx));
}
/* The four core functions - F1 is optimized somewhat */
/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))
/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f,w,x,y,z,in,s) \
(w += f(x,y,z) + in, w = (w<<s | w>>(32-s)) + x)
/*
* The core of the MD5 algorithm, this alters an existing MD5 hash to
* reflect the addition of 16 longwords of new data. MD5Update blocks
* the data and converts bytes into longwords for this routine.
*/
void
xMD5Transform(ULONG buf[4], ULONG const in[16])
{
register ULONG a, b, c, d;
a = buf[0];
b = buf[1];
c = buf[2];
d = buf[3];
MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
buf[0] += a;
buf[1] += b;
buf[2] += c;
buf[3] += d;
}
void MD5(void *dest, void *orig, int len)
{
struct xMD5Context context;
xMD5Init(&context);
xMD5Update(&context, orig, len);
xMD5Final(dest, &context);
}
/*****************************************************************/
// -------------------------------
void load_seed( void );
void save_seed( void );
ULONG md5_rnd( ULONG, ULONG );
// -------------------------------
static unsigned long digest[4];
void load_seed()
{
int fd;
fd = open(_md5digestname, O_RDONLY);
if (fd >= 0)
{
read(fd, digest, 16);
close(fd);
}
}
void save_seed()
{
int fd;
fd = open(_md5digestname, O_WRONLY|O_CREAT, 0600);
if (fd >= 0)
{
write(fd, digest, 16);
close(fd);
}
}
ULONG md5_rnd(ULONG low, ULONG high)
{
ULONG range = high - low;
ULONG mask = 0;
ULONG num;
int r;
for (r = range; r; r >>= 1)
mask |= r;
do {
MD5(digest, digest, sizeof(digest));
num = digest[0] & mask;
} while (num > range);
return (num + low);
}