git.distorted.org.uk Git - u/mdw/catacomb/blob - ec-raw.c

   1 /* -*-c-*-
   2  *
   3  * $Id: ec-raw.c,v 1.1 2004/04/04 19:04:11 mdw Exp $
   4  *
   5  * Raw formatting of elliptic curve points
   6  *
   7  * (c) 2004 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: ec-raw.c,v $
  33  * Revision 1.1  2004/04/04 19:04:11  mdw
  34  * Raw I/O of elliptic curve points and group elements.
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 #include "ec.h"
  41 #include "ec-raw.h"
  42
  43 /*----- Main code ---------------------------------------------------------*/
  44
  45 /* --- @ec_putraw@ --- *
  46  *
  47  * Arguments:   @ec_curve *c@ = elliptic curve
  48  *              @buf *b@ = pointer to a buffer
  49  *              @const ec *p@ = an elliptic curve point
  50  *
  51  * Returns:     Zero on success, nonzero on failure.
  52  *
  53  * Use:         Puts an elliptic curve point to the given buffer using the
  54  *              standard uncompressed format described in P1383 and SEC1.
  55  *              This requires at most @1 + 2 * c->f->noctets@ space in the
  56  *              buffer.  We don't do point compression.
  57  */
  58
  59 int ec_putraw(ec_curve *c, buf *b, const ec *p)
  60 {
  61   octet *q;
  62   size_t n;
  63
  64   if (EC_ATINF(p)) return (buf_putbyte(b, 0));
  65   buf_putbyte(b, 4);
  66   n = c->f->noctets;
  67   if ((q = buf_get(b, n * 2)) == 0) return (-1);
  68   mp_storeb(p->x, q, n);
  69   mp_storeb(p->y, q + n, n);
  70   return (0);
  71 }
  72
  73 /* --- @ec_getraw@ --- *
  74  *
  75  * Arguments:   @ec_curve *c@ = elliptic curve
  76  *              @buf *b@ = pointer to a buffer
  77  *              @ec *d@ = an elliptic curve point
  78  *
  79  * Returns:     Zero on success, nonzero on failure.
  80  *
  81  * Use:         Reads an elliptic curve point from the given buffer using the
  82  *              standard uncompressed format described in P1383 and SEC1.
  83  *              We don't do point compression.
  84  */
  85
  86 int ec_getraw(ec_curve *c, buf *b, ec *d)
  87 {
  88   const octet *q;
  89   size_t n;
  90   int u;
  91
  92   if ((u = buf_getbyte(b)) < 0) return (-1);
  93   if (!u) { EC_SETINF(d); return (0); }
  94   if (!(u & 4)) return (-1);
  95   n = c->f->noctets;
  96   if ((q = buf_get(b, n * 2)) == 0) return (-1);
  97   EC_DESTROY(d);
  98   d->x = mp_loadb(MP_NEW, q, n);
  99   d->y = mp_loadb(MP_NEW, q + n, n);
 100   d->z = 0;
 101   return (0);
 102 }
 103
 104 /*----- That's all, folks -------------------------------------------------*/