blob: cf35f0436d2db7fe79d385c835ecc7e8d25f9d3e [file] [log] [blame]
 #include "os.h" #include #include DSApriv* dsagen(DSApub *opub) { DSApub *pub; DSApriv *priv; mpint *exp; mpint *g; mpint *r; int bits; priv = dsaprivalloc(); pub = &priv->pub; if(opub != nil){ pub->p = mpcopy(opub->p); pub->q = mpcopy(opub->q); } else { pub->p = mpnew(0); pub->q = mpnew(0); DSAprimes(pub->q, pub->p, nil); } bits = Dbits*pub->p->top; pub->alpha = mpnew(0); pub->key = mpnew(0); priv->secret = mpnew(0); /* find a generator alpha of the multiplicative */ /* group Z*p, i.e., of order n = p-1. We use the */ /* fact that q divides p-1 to reduce the exponent. */ exp = mpnew(0); g = mpnew(0); r = mpnew(0); mpsub(pub->p, mpone, exp); mpdiv(exp, pub->q, exp, r); if(mpcmp(r, mpzero) != 0) sysfatal("dsagen foul up"); while(1){ mprand(bits, genrandom, g); mpmod(g, pub->p, g); mpexp(g, exp, pub->p, pub->alpha); if(mpcmp(pub->alpha, mpone) != 0) break; } mpfree(g); mpfree(exp); /* create the secret key */ mprand(bits, genrandom, priv->secret); mpmod(priv->secret, pub->p, priv->secret); mpexp(pub->alpha, priv->secret, pub->p, pub->key); return priv; }