cirno/plan9port
1
0
Fork 0
mirror of https://github.com/9fans/plan9port.git synced 2025-01-12 11:10:07 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

probably_prime: run more than one Miller-Rabin round

Browse source 
R=rsc
http://codereview.appspot.com/462041
This commit is contained in:
Russ Cox 2010-03-11 18:04:42 -08:00
parent a1afc8529d
commit 1619f52cbc
1 changed files with 17 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

29
src/libsec/port/probably_prime.c
View file

@ -9,7 +9,7 @@
int
probably_prime(mpint *n, int nrep)
{
int j, k, rep, nbits, isprime = 1;
int j, k, rep, nbits, isprime;
mpint *nm1, *q, *x, *y, *r;
if(n->sign < 0)
@ -49,32 +49,37 @@ probably_prime(mpint *n, int nrep)
mpright(nm1, k, q); /* q = (n-1)/2**k */
for(rep = 0; rep < nrep; rep++){
/* x = random in [2, n-2] */
r = mprand(nbits, prng, nil);
mpmod(r, nm1, x);
mpfree(r);
if(mpcmp(x, mpone) <= 0)
continue;
for(;;){
/* find x = random in [2, n-2] */
r = mprand(nbits, prng, nil);
mpmod(r, nm1, x);
mpfree(r);
if(mpcmp(x, mpone) > 0)
break;
}
/* y = x**q mod n */
mpexp(x, q, n, y);
if(mpcmp(y, mpone) == 0 || mpcmp(y, nm1) == 0)
goto done;
continue;
for(j = 1; j < k; j++){
for(j = 1;; j++){
if(j >= k) {
isprime = 0;
goto done;
}
mpmul(y, y, x);
mpmod(x, n, y); /* y = y*y mod n */
if(mpcmp(y, nm1) == 0)
goto done;
break;
if(mpcmp(y, mpone) == 0){
isprime = 0;
goto done;
}
}
isprime = 0;
}
isprime = 1;
done:
mpfree(y);
mpfree(x);