ref: 5171a0ac52a02cbeca41608ab1824c1250a087a4
dir: /sys/src/libsec/port/genprime.c/
#include "os.h"
#include <mp.h>
#include <libsec.h>
// generate a probable prime. accuracy is the miller-rabin interations
void
genprime(mpint *p, int n, int accuracy)
{
mpdigit x;
// generate n random bits with high and low bits set
mpbits(p, n);
genrandom((uchar*)p->p, (n+7)/8);
p->top = (n+Dbits-1)/Dbits;
x = 1;
x <<= ((n-1)%Dbits);
p->p[p->top-1] &= (x-1);
p->p[p->top-1] |= x;
p->p[0] |= 1;
mpnorm(p);
// keep icrementing till it looks prime
for(;;){
if(probably_prime(p, accuracy))
break;
mpadd(p, mptwo, p);
}
}