Add consistency checking for public keys.

[u/mdw/catacomb] / dsa-check.c

diff --git a/dsa-check.c b/dsa-check.c
new file mode 100644 (file)
index 0000000..88a5686
--- /dev/null
+++ b/dsa-check.c
@@ -0,0 +1,97 @@
+/* -*-c-*-
+ *
+ * $Id: dsa-check.c,v 1.1 2001/02/03 16:08:24 mdw Exp $
+ *
+ * Consistency checking for DSA keys
+ *
+ * (c) 2001 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: dsa-check.c,v $
+ * Revision 1.1  2001/02/03 16:08:24  mdw
+ * Add consistency checking for public keys.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "dh.h"
+#include "dsa.h"
+#include "dsarand.h"
+#include "grand.h"
+#include "keycheck.h"
+#include "mp.h"
+#include "mprand.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @dsa_checkparam@ --- *
+ *
+ * Arguments:  @keycheck *kc@ = keycheck state
+ *             @const dsa_param *dp@ = pointer to the parameter set
+ *             @const dsa_seed *ds@ = pointer to seed information
+ *
+ * Returns:    Zero if all OK, or return status from function.
+ *
+ * Use:                Checks a set of DSA parameters for consistency and security.
+ */
+
+int dsa_checkparam(keycheck *kc, const dsa_param *dp, const dsa_seed *ds)
+{
+  if (ds) {
+    grand *r = dsarand_create(ds->p, ds->sz);
+    mp *p = MP_NEW, *q = MP_NEW;
+    int rc = 0;
+    unsigned i;
+    unsigned long n;
+
+    r->ops->misc(r, DSARAND_PASSES, 2);
+    q = mprand(q, mp_bits(dp->q), r, 1);
+    if (!mp_eq(q, dp->q) &&
+       keycheck_report(kc, KCSEV_ERR, "q doesn't match seed provided"))
+      rc = -1;
+    else {
+      n = mp_bits(dp->p);
+      r->ops->misc(r, DSARAND_PASSES, 1);
+      for (i = 0; i <= ds->count; i++)
+       p = mprand(p, n, r, 0);
+      q = mp_lsl(q, q, 1);
+      mp_div(0, &q, p, q);
+      p = mp_sub(p, p, q);
+      p->v[0] |= 1;
+      if (!mp_eq(p, dp->p) &&
+         keycheck_report(kc, KCSEV_ERR, "p doesn't match seed provided"))
+       rc = -1;
+    }
+    mp_drop(p);
+    mp_drop(q);
+    r->ops->destroy(r);
+    if (rc)
+      return (rc);
+  }
+  return (dh_checkparam(kc, dp, 0, 0));
+}
+
+/*----- That's all, folks -------------------------------------------------*/