New function and example program computes Fibonacci numbers fairly fast.

[u/mdw/catacomb] / gfshare.h

diff --git a/gfshare.h b/gfshare.h
index 1e1f984..9826758 100644 (file)
--- a/gfshare.h
+++ b/gfshare.h
@@ -1,13 +1,13 @@
 /* -*-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.
  *
@@ -15,36 +15,18 @@
  * 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
@@ -85,11 +67,12 @@ typedef struct gfshare {
   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 ------------------------------------------------*/
 
@@ -123,18 +106,20 @@ extern void gfshare_destroy(gfshare */*s*/);
  *
  * 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@ --- *
  *
@@ -142,7 +127,7 @@ extern void gfshare_mkshares(gfshare */*s*/, grand */*r*/);
  *             @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.
@@ -150,6 +135,17 @@ extern void gfshare_mkshares(gfshare */*s*/, grand */*r*/);
 
 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