Raw I/O of elliptic curve points and group elements.

[u/mdw/catacomb] / ec-raw.c

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+/* -*-c-*-
+ *
+ * $Id: ec-raw.c,v 1.1 2004/04/04 19:04:11 mdw Exp $
+ *
+ * Raw formatting of elliptic curve points
+ *
+ * (c) 2004 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: ec-raw.c,v $
+ * Revision 1.1  2004/04/04 19:04:11  mdw
+ * Raw I/O of elliptic curve points and group elements.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "ec.h"
+#include "ec-raw.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @ec_putraw@ --- *
+ *
+ * Arguments:  @ec_curve *c@ = elliptic curve
+ *             @buf *b@ = pointer to a buffer
+ *             @const ec *p@ = an elliptic curve point
+ *
+ * Returns:    Zero on success, nonzero on failure.
+ *
+ * Use:                Puts an elliptic curve point to the given buffer using the
+ *             standard uncompressed format described in P1383 and SEC1.
+ *             This requires at most @1 + 2 * c->f->noctets@ space in the
+ *             buffer.  We don't do point compression.
+ */
+
+int ec_putraw(ec_curve *c, buf *b, const ec *p)
+{
+  octet *q;
+  size_t n;
+
+  if (EC_ATINF(p)) return (buf_putbyte(b, 0));
+  buf_putbyte(b, 4);
+  n = c->f->noctets;
+  if ((q = buf_get(b, n * 2)) == 0) return (-1);
+  mp_storeb(p->x, q, n);
+  mp_storeb(p->y, q + n, n);
+  return (0);
+}
+
+/* --- @ec_getraw@ --- *
+ *
+ * Arguments:  @ec_curve *c@ = elliptic curve
+ *             @buf *b@ = pointer to a buffer
+ *             @ec *d@ = an elliptic curve point
+ *
+ * Returns:    Zero on success, nonzero on failure.
+ *
+ * Use:                Reads an elliptic curve point from the given buffer using the
+ *             standard uncompressed format described in P1383 and SEC1.
+ *             We don't do point compression.
+ */
+
+int ec_getraw(ec_curve *c, buf *b, ec *d)
+{
+  const octet *q;
+  size_t n;
+  int u;
+
+  if ((u = buf_getbyte(b)) < 0) return (-1);
+  if (!u) { EC_SETINF(d); return (0); }
+  if (!(u & 4)) return (-1);
+  n = c->f->noctets;
+  if ((q = buf_get(b, n * 2)) == 0) return (-1);
+  EC_DESTROY(d);
+  d->x = mp_loadb(MP_NEW, q, n);
+  d->y = mp_loadb(MP_NEW, q + n, n);
+  d->z = 0;
+  return (0);
+}
+
+/*----- That's all, folks -------------------------------------------------*/