/* -*-c-*-
*
- * $Id: rsa-recover.c,v 1.1 1999/12/22 15:50:45 mdw Exp $
+ * $Id: rsa-recover.c,v 1.2 2000/06/17 12:07:19 mdw Exp $
*
* Recover RSA parameters
*
/*----- Revision history --------------------------------------------------*
*
* $Log: rsa-recover.c,v $
+ * Revision 1.2 2000/06/17 12:07:19 mdw
+ * Fix a bug in argument validation. Force %$p > q$% in output. Use
+ * %$\lambda(n) = \lcm(p - 1, q - 1)$% rather than the more traditional
+ * %$\phi(n) = (p - 1)(q - 1)$% when computing the decryption exponent.
+ *
* Revision 1.1 1999/12/22 15:50:45 mdw
* Initial RSA support.
*
/* --- Otherwise use the public and private moduli --- */
- else if (rp->e && rp->d) {
+ else if (!rp->e || !rp->d)
+ return (-1);
+ else {
mp *t;
unsigned s;
mpscan ms;
mp_drop(z);
mp_drop(t);
mp_drop(m1);
+ if (MP_CMP(rp->p, <, rp->q)) {
+ z = rp->p;
+ rp->p = rp->q;
+ rp->q = z;
+ }
mpmont_destroy(&mm);
}
}
if (!rp->e || !rp->d) {
mp *phi;
mp *g = MP_NEW;
+ mp *p1, *q1;
/* --- Compute %$\varphi(n)$% --- */
phi = mp_sub(MP_NEW, rp->n, rp->p);
phi = mp_sub(phi, phi, rp->q);
phi = mp_add(phi, phi, MP_ONE);
+ p1 = mp_sub(MP_NEW, rp->p, MP_ONE);
+ q1 = mp_sub(MP_NEW, rp->q, MP_ONE);
+ mp_gcd(&g, 0, 0, p1, q1);
+ mp_div(&phi, 0, phi, g);
+ mp_drop(p1);
+ mp_drop(q1);
/* --- Recover the other exponent --- */
mp_gcd(&g, 0, &rp->e, phi, rp->d);
else {
mp_drop(phi);
+ mp_drop(g);
return (-1);
}