/* -*-c-*-
*
- * $Id: gfshare.h,v 1.4 2000/06/24 18:29:05 mdw Exp $
+ * $Id$
*
* Secret sharing over %$\gf{2^8}$%
*
* (c) 2000 Straylight/Edgeware
*/
-/*----- Licensing notice --------------------------------------------------*
+/*----- Licensing notice --------------------------------------------------*
*
* This file is part of Catacomb.
*
* 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: gfshare.h,v $
- * Revision 1.4 2000/06/24 18:29:05 mdw
- * Interface change: allow shares to be extracted from a context on demand,
- * rather than building them all up-front.
- *
- * Revision 1.3 2000/06/18 23:12:15 mdw
- * Change typesetting of Galois Field names.
- *
- * Revision 1.2 2000/06/17 11:05:27 mdw
- * Add a commentary on the system.
- *
- * Revision 1.1 2000/06/17 10:56:30 mdw
- * Fast but nonstandard secret sharing system.
- *
- */
-
/*----- Notes on the system -----------------------------------------------*
*
* This uses a variant of Shamir's secret sharing system. Shamir's original
unsigned t; /* Threshold */
unsigned i; /* Next free slot in vector */
size_t sz; /* Size of the secret and shares */
- void *s; /* The secret */
octet *v; /* Vector of share information */
} gfshare;
-#define GFSHARE_INIT(t, sz) { t, 0, sz, 0, 0 }
+#define GFSHARE_INIT(t, sz) { t, 0, sz, 0 }
+
+#define GFSHARE_INDEX(s, i) ((s)->v[(i) * ((s)->sz + 1)])
/*----- Functions provided ------------------------------------------------*/
*
* Arguments: @gfshare *s@ = pointer to share context to fill in
* @grand *r@ = pointer to random number source
+ * @const void *buf@ = pointer to the secret to share
*
* Returns: ---
*
* Use: Initializes a sharing context to be able to create shares.
* The context structure is expected to be mostly filled in. In
- * particular, @t@ and @s@ must be initialized. If @v@ is zero,
- * a vector of appropriate size is allocated. You should use
- * the macro @GFSHARE_INIT@ or @gfshare_create@ to construct
- * sharing contexts.
+ * particular, @t@ must be initialized. If @v@ is zero, a
+ * vector of appropriate size is allocated. You should use the
+ * macro @GFSHARE_INIT@ or @gfshare_create@ to construct sharing
+ * contexts.
*/
-extern void gfshare_mkshares(gfshare */*s*/, grand */*r*/);
+extern void gfshare_mkshares(gfshare */*s*/, grand */*r*/,
+ const void */*buf*/);
/* --- @gfshare_get@ --- *
*
* @unsigned x@ = share index to fetch
* @void *buf@ = pointer to output buffer
*
- * Returns: The share, as requested.
+ * Returns: ---
*
* Use: Extracts a share from the system. You may extract up to 255
* shares from the system. Shares are indexed from 0.
extern void gfshare_get(gfshare */*s*/, unsigned /*x*/, void */*buf*/);
+/* --- @gfshare_addedp@ --- *
+ *
+ * Arguments: @gfshare *s@ = pointer to sharing context
+ * @unsigned x@ = which share number to check
+ *
+ * Returns: Nonzero if share @x@ has been added already, zero if it
+ * hasn't.
+ */
+
+extern int gfshare_addedp(gfshare */*s*/, unsigned /*x*/);
+
/* --- @gfshare_add@ --- *
*
* Arguments: @gfshare *s@ = pointer to sharing context