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

   1 /* -*-c-*-
   2  *
   3  * $Id: ec-raw.c,v 1.2 2004/04/08 01:36:15 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 /*----- Header files ------------------------------------------------------*/
  31
  32 #include "ec.h"
  33 #include "ec-raw.h"
  34
  35 /*----- Main code ---------------------------------------------------------*/
  36
  37 /* --- @ec_putraw@ --- *
  38  *
  39  * Arguments:   @ec_curve *c@ = elliptic curve
  40  *              @buf *b@ = pointer to a buffer
  41  *              @const ec *p@ = an elliptic curve point
  42  *
  43  * Returns:     Zero on success, nonzero on failure.
  44  *
  45  * Use:         Puts an elliptic curve point to the given buffer using the
  46  *              standard uncompressed format described in P1383 and SEC1.
  47  *              This requires at most @1 + 2 * c->f->noctets@ space in the
  48  *              buffer.  We don't do point compression.
  49  */
  50
  51 int ec_putraw(ec_curve *c, buf *b, const ec *p)
  52 {
  53   octet *q;
  54   size_t n;
  55
  56   if (EC_ATINF(p)) return (buf_putbyte(b, 0));
  57   buf_putbyte(b, 4);
  58   n = c->f->noctets;
  59   if ((q = buf_get(b, n * 2)) == 0) return (-1);
  60   mp_storeb(p->x, q, n);
  61   mp_storeb(p->y, q + n, n);
  62   return (0);
  63 }
  64
  65 /* --- @ec_getraw@ --- *
  66  *
  67  * Arguments:   @ec_curve *c@ = elliptic curve
  68  *              @buf *b@ = pointer to a buffer
  69  *              @ec *d@ = an elliptic curve point
  70  *
  71  * Returns:     Zero on success, nonzero on failure.
  72  *
  73  * Use:         Reads an elliptic curve point from the given buffer using the
  74  *              standard uncompressed format described in P1383 and SEC1.
  75  *              We don't do point compression.
  76  */
  77
  78 int ec_getraw(ec_curve *c, buf *b, ec *d)
  79 {
  80   const octet *q;
  81   size_t n;
  82   int u;
  83
  84   if ((u = buf_getbyte(b)) < 0) return (-1);
  85   if (!u) { EC_SETINF(d); return (0); }
  86   if (!(u & 4)) return (-1);
  87   n = c->f->noctets;
  88   if ((q = buf_get(b, n * 2)) == 0) return (-1);
  89   EC_DESTROY(d);
  90   d->x = mp_loadb(MP_NEW, q, n);
  91   d->y = mp_loadb(MP_NEW, q + n, n);
  92   d->z = 0;
  93   return (0);
  94 }
  95
  96 /*----- That's all, folks -------------------------------------------------*/