Renamed from `rsa-decrypt', since the name was no longer appropriate.

[u/mdw/catacomb] / rsa-recover.c

diff --git a/rsa-recover.c b/rsa-recover.c
index c125aef..304cbca 100644 (file)
--- a/rsa-recover.c
+++ b/rsa-recover.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: rsa-recover.c,v 1.1 1999/12/22 15:50:45 mdw Exp $
+ * $Id: rsa-recover.c,v 1.4 2000/07/01 11:22:22 mdw Exp $
  *
  * Recover RSA parameters
  *
@@ -30,6 +30,17 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: rsa-recover.c,v $
+ * Revision 1.4  2000/07/01 11:22:22  mdw
+ * Remove bad type name `rsa_param'.
+ *
+ * Revision 1.3  2000/06/22 19:03:14  mdw
+ * Use the new @mp_odd@ function.
+ *
+ * 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.
  *
@@ -45,7 +56,7 @@
 
 /* --- @rsa_recover@ --- *
  *
- * Arguments:  @rsa_param *rp@ = pointer to parameter block
+ * Arguments:  @rsa_priv *rp@ = pointer to parameter block
  *
  * Returns:    Zero if all went well, nonzero if the parameters make no
  *             sense.
@@ -53,7 +64,7 @@
  * Use:                Derives the full set of RSA parameters given a minimal set.
  */
 
-int rsa_recover(rsa_param *rp)
+int rsa_recover(rsa_priv *rp)
 {
   /* --- If there is no modulus, calculate it --- */
 
@@ -84,10 +95,11 @@ int rsa_recover(rsa_param *rp)
 
     /* --- 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;
+      size_t s;
       mp a; mpw aw;
       mp *m1;
       mpmont mm;
@@ -102,15 +114,7 @@ int rsa_recover(rsa_param *rp)
 
       t = mp_mul(MP_NEW, rp->e, rp->d);
       t = mp_sub(t, t, MP_ONE);
-      s = 0;
-      mp_scan(&ms, t);
-      for (;;) {
-       MP_STEP(&ms);
-       if (MP_BIT(&ms))
-         break;
-       s++;
-      }
-      t = mp_lsr(t, t, s);
+      t = mp_odd(t, t, &s);
 
       /* --- Set up for the exponentiation --- */
 
@@ -182,6 +186,11 @@ int rsa_recover(rsa_param *rp)
       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);
     }
   }
@@ -191,12 +200,19 @@ int rsa_recover(rsa_param *rp)
   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 --- */
 
@@ -206,6 +222,7 @@ int rsa_recover(rsa_param *rp)
       mp_gcd(&g, 0, &rp->e, phi, rp->d);
     else {
       mp_drop(phi);
+      mp_drop(g);
       return (-1);
     }