98 lines
1.8 KiB
C
98 lines
1.8 KiB
C
#include "os.h"
|
|
#include <mp.h>
|
|
#include <libsec.h>
|
|
|
|
// NIST algorithm for generating DSA primes
|
|
// Menezes et al (1997) Handbook of Applied Cryptography, p.151
|
|
// q is a 160-bit prime; p is a 1024-bit prime; q divides p-1
|
|
|
|
// arithmetic on unsigned ints mod 2**160, represented
|
|
// as 20-byte, little-endian uchar array
|
|
|
|
static void
|
|
Hrand(uchar *s)
|
|
{
|
|
ulong *u = (ulong*)s;
|
|
*u++ = fastrand();
|
|
*u++ = fastrand();
|
|
*u++ = fastrand();
|
|
*u++ = fastrand();
|
|
*u = fastrand();
|
|
}
|
|
|
|
static void
|
|
Hincr(uchar *s)
|
|
{
|
|
int i;
|
|
for(i=0; i<20; i++)
|
|
if(++s[i]!=0)
|
|
break;
|
|
}
|
|
|
|
// this can run for quite a while; be patient
|
|
void
|
|
DSAprimes(mpint *q, mpint *p, uchar seed[SHA1dlen])
|
|
{
|
|
int i, j, k, n = 6, b = 63;
|
|
uchar s[SHA1dlen], Hs[SHA1dlen], Hs1[SHA1dlen], sj[SHA1dlen], sjk[SHA1dlen];
|
|
mpint *two1023, *mb, *Vk, *W, *X, *q2;
|
|
|
|
two1023 = mpnew(1024);
|
|
mpleft(mpone, 1023, two1023);
|
|
mb = mpnew(0);
|
|
mpleft(mpone, b, mb);
|
|
W = mpnew(1024);
|
|
Vk = mpnew(1024);
|
|
X = mpnew(0);
|
|
q2 = mpnew(0);
|
|
forever:
|
|
do{
|
|
Hrand(s);
|
|
memcpy(sj, s, 20);
|
|
sha1(s, 20, Hs, 0);
|
|
Hincr(sj);
|
|
sha1(sj, 20, Hs1, 0);
|
|
for(i=0; i<20; i++)
|
|
Hs[i] ^= Hs1[i];
|
|
Hs[0] |= 1;
|
|
Hs[19] |= 0x80;
|
|
letomp(Hs, 20, q);
|
|
}while(!probably_prime(q, 18));
|
|
if(seed != nil) // allow skeptics to confirm computation
|
|
memmove(seed, s, SHA1dlen);
|
|
i = 0;
|
|
j = 2;
|
|
Hincr(sj);
|
|
mpleft(q, 1, q2);
|
|
while(i<4096){
|
|
memcpy(sjk, sj, 20);
|
|
for(k=0; k <= n; k++){
|
|
sha1(sjk, 20, Hs, 0);
|
|
letomp(Hs, 20, Vk);
|
|
if(k == n)
|
|
mpmod(Vk, mb, Vk);
|
|
mpleft(Vk, 160*k, Vk);
|
|
mpadd(W, Vk, W);
|
|
Hincr(sjk);
|
|
}
|
|
mpadd(W, two1023, X);
|
|
mpmod(X, q2, W);
|
|
mpsub(W, mpone, W);
|
|
mpsub(X, W, p);
|
|
if(mpcmp(p, two1023)>=0 && probably_prime(p, 5))
|
|
goto done;
|
|
i += 1;
|
|
j += n+1;
|
|
for(k=0; k<n+1; k++)
|
|
Hincr(sj);
|
|
}
|
|
goto forever;
|
|
done:
|
|
mpfree(q2);
|
|
mpfree(X);
|
|
mpfree(Vk);
|
|
mpfree(W);
|
|
mpfree(mb);
|
|
mpfree(two1023);
|
|
}
|