/* -*-c-*-
*
- * $Id: gfshare.h,v 1.3 2000/06/18 23:12:15 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 1.3 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
/* --- A secret sharing context --- */
-typedef struct gfshare_pt {
- octet x; /* %$x$%-coordinate of the share */
- octet *y; /* Pointer to share payload */
-} gfshare_pt;
-
typedef struct gfshare {
unsigned t; /* Threshold */
- unsigned n; /* The number of shares to make */
unsigned i; /* Next free slot in vector */
size_t sz; /* Size of the secret and shares */
- octet *s; /* The secret */
- gfshare_pt *v; /* Vector of share information */
+ octet *v; /* Vector of share information */
} gfshare;
-#define GFSHARE_INIT(t, n, sz) { t, n, 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 ------------------------------------------------*/
/* --- @gfshare_create@ --- *
*
* Arguments: @gfshare *s@ = pointer to share context to initialize
- * @unsigned t, n@ = threshold parameters for the system
+ * @unsigned t@ = threshold for the system
* @size_t sz@ = size of the secret
*
* Returns: ---
* Use: Initializes a sharing context.
*/
-extern void gfshare_create(gfshare */*s*/, unsigned /*t*/, unsigned /*n*/,
- size_t /*sz*/);
+extern void gfshare_create(gfshare */*s*/, unsigned /*t*/, size_t /*sz*/);
/* --- @gfshare_destroy@ --- *
*
*
* 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: Generates @c->n@ secret shares, such that any @c->t@ of them
- * may be used to recover the secret.
- *
+ * Use: Initializes a sharing context to be able to create shares.
* The context structure is expected to be mostly filled in. In
- * particular, @t@, @n@, @ssz@ 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*/,
+ const void */*buf*/);
+
+/* --- @gfshare_get@ --- *
+ *
+ * Arguments: @gfshare *s@ = pointer to share conext
+ * @unsigned x@ = share index to fetch
+ * @void *buf@ = pointer to output buffer
+ *
+ * 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 void gfshare_mkshares(gfshare */*s*/, grand */*r*/);
+extern int gfshare_addedp(gfshare */*s*/, unsigned /*x*/);
/* --- @gfshare_add@ --- *
*
* Arguments: @gfshare *s@ = pointer to sharing context
* @unsigned x@ = which share number this is
- * @const octet *y@ = the share value
+ * @const void *y@ = the share value
*
* Returns: Number of shares required before recovery may be performed.
*
*/
extern unsigned gfshare_add(gfshare */*s*/,
- unsigned /*x*/, const octet */*y*/);
+ unsigned /*x*/, const void */*y*/);
/* --- @gfshare_combine@ --- *
*
* Arguments: @gfshare *s@ = pointer to share context
- * @octet *buf@ = pointer to output buffer for the secret
+ * @void *buf@ = pointer to output buffer for the secret
*
* Returns: ---
*
* Use: Reconstructs a secret, given enough shares.
*/
-extern void gfshare_combine(gfshare */*s*/, octet */*buf*/);
+extern void gfshare_combine(gfshare */*s*/, void */*buf*/);
/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff