ref: 1125f094ce2a6854ef568b8c62602ce07c6a2935
dir: /libsec/egverify.c/
#include "os.h"
#include <mp.h>
#include <libsec.h>
int
egverify(EGpub *pub, EGsig *sig, mpint *m)
{
mpint *p = pub->p, *alpha = pub->alpha;
mpint *r = sig->r, *s = sig->s;
mpint *v1, *v2, *rs;
int rv = -1;
if(mpcmp(r, mpone) < 0 || mpcmp(r, p) >= 0)
return rv;
v1 = mpnew(0);
rs = mpnew(0);
v2 = mpnew(0);
mpexp(pub->key, r, p, v1);
mpexp(r, s, p, rs);
mpmul(v1, rs, v1);
mpmod(v1, p, v1);
mpexp(alpha, m, p, v2);
if(mpcmp(v1, v2) == 0)
rv = 0;
mpfree(v1);
mpfree(rs);
mpfree(v2);
return rv;
}