git.distorted.org.uk Git - u/mdw/catacomb/blob - dsa-check.c

   1 /* -*-c-*-
   2  *
   3  * $Id: dsa-check.c,v 1.1 2001/02/03 16:08:24 mdw Exp $
   4  *
   5  * Consistency checking for DSA keys
   6  *
   7  * (c) 2001 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: dsa-check.c,v $
  33  * Revision 1.1  2001/02/03 16:08:24  mdw
  34  * Add consistency checking for public keys.
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 #include "dh.h"
  41 #include "dsa.h"
  42 #include "dsarand.h"
  43 #include "grand.h"
  44 #include "keycheck.h"
  45 #include "mp.h"
  46 #include "mprand.h"
  47
  48 /*----- Main code ---------------------------------------------------------*/
  49
  50 /* --- @dsa_checkparam@ --- *
  51  *
  52  * Arguments:   @keycheck *kc@ = keycheck state
  53  *              @const dsa_param *dp@ = pointer to the parameter set
  54  *              @const dsa_seed *ds@ = pointer to seed information
  55  *
  56  * Returns:     Zero if all OK, or return status from function.
  57  *
  58  * Use:         Checks a set of DSA parameters for consistency and security.
  59  */
  60
  61 int dsa_checkparam(keycheck *kc, const dsa_param *dp, const dsa_seed *ds)
  62 {
  63   if (ds) {
  64     grand *r = dsarand_create(ds->p, ds->sz);
  65     mp *p = MP_NEW, *q = MP_NEW;
  66     int rc = 0;
  67     unsigned i;
  68     unsigned long n;
  69
  70     r->ops->misc(r, DSARAND_PASSES, 2);
  71     q = mprand(q, mp_bits(dp->q), r, 1);
  72     if (!mp_eq(q, dp->q) &&
  73         keycheck_report(kc, KCSEV_ERR, "q doesn't match seed provided"))
  74       rc = -1;
  75     else {
  76       n = mp_bits(dp->p);
  77       r->ops->misc(r, DSARAND_PASSES, 1);
  78       for (i = 0; i <= ds->count; i++)
  79         p = mprand(p, n, r, 0);
  80       q = mp_lsl(q, q, 1);
  81       mp_div(0, &q, p, q);
  82       p = mp_sub(p, p, q);
  83       p->v[0] |= 1;
  84       if (!mp_eq(p, dp->p) &&
  85           keycheck_report(kc, KCSEV_ERR, "p doesn't match seed provided"))
  86         rc = -1;
  87     }
  88     mp_drop(p);
  89     mp_drop(q);
  90     r->ops->destroy(r);
  91     if (rc)
  92       return (rc);
  93   }
  94   return (dh_checkparam(kc, dp, 0, 0));
  95 }
  96
  97 /*----- That's all, folks -------------------------------------------------*/