#include <libsec.h>

#include "os.h"
#include <mp.h>
#include <libsec.h>

EGsig*
egsign(EGpriv *priv, mpint *m)
{
EGpub *pub = &priv->pub;
EGsig *sig;
mpint *pm1, *k, *kinv, *r, *s;
mpint *p = pub->p, *alpha = pub->alpha;
int plen = mpsignif(p);

pm1 = mpnew(0);
kinv = mpnew(0);
r = mpnew(0);
s = mpnew(0);
k = mpnew(0);
mpsub(p, mpone, pm1);
while(1){
mprand(plen, genrandom, k);
if((mpcmp(mpone, k) > 0) || (mpcmp(k, pm1) >= 0))
continue;
mpextendedgcd(k, pm1, r, kinv, s);
if(mpcmp(r, mpone) != 0)
continue;
break;
}
mpmod(kinv, pm1, kinv); // make kinv positive
mpexp(alpha, k, p, r);
mpmul(priv->secret, r, s);
mpmod(s, pm1, s);
mpsub(m, s, s);
mpmul(kinv, s, s);
mpmod(s, pm1, s);
sig = egsigalloc();
sig->r = r;
sig->s = s;
mpfree(pm1);
mpfree(k);
mpfree(kinv);
return sig;
}