+++ /dev/null
-/* -*-c-*-
- *
- * $Id$
- *
- * Shamir's secret sharing
- *
- * (c) 2000 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.
- */
-
-/*----- Notes on the sharing system ---------------------------------------*
- *
- * Shamir's secret-sharing system is based on polynomial interpolation modulo
- * a prime number. It is `perfect' in that fewer participants than the
- * threshold can derive no information about the secret by pooling their
- * shares, and `ideal' in that the shares are the same size as the secret.
- *
- * This implementation stays close to the definition, in order to support
- * other schemes for (e.g.) threshold cryptography. It is, however, rather
- * slow.
- */
-
-#ifndef CATACOMB_SHARE_H
-#define CATACOMB_SHARE_H
-
-#ifdef __cplusplus
- extern "C" {
-#endif
-
-/*----- Header files ------------------------------------------------------*/
-
-#ifndef CATACOMB_GRAND_H
-# include "grand.h"
-#endif
-
-#ifndef CATACOMB_MP_H
-# include "mp.h"
-#endif
-
-/*----- Data structures ---------------------------------------------------*/
-
-/* --- A secret sharing context --- */
-
-typedef struct share_pt {
- unsigned x; /* Index of this share */
- mp *y; /* Payload of this share */
-} share_pt;
-
-typedef struct share {
- unsigned t; /* Threshold */
- unsigned i; /* Next free slot in the vector */
- mp *p; /* Modulus for arithmetic */
- share_pt *v; /* Vector of share information */
-} share;
-
-#define SHARE_INIT(t) { t, 0, 0, 0 }
-
-/*----- Functions provided ------------------------------------------------*/
-
-/* --- @share_create@ --- *
- *
- * Arguments: @share *s@ = pointer to share context to initialize
- * @unsigned t@ = threshold for the system
- *
- * Returns: ---
- *
- * Use: Initializes a sharing context.
- */
-
-extern void share_create(share */*s*/, unsigned /*t*/);
-
-/* --- @share_destroy@ --- *
- *
- * Arguments: @share *s@ = pointer to share context to destroy
- *
- * Returns: ---
- *
- * Use: Disposes of a sharing context. All memory is freed, all
- * integers are dropped.
- */
-
-extern void share_destroy(share */*s*/);
-
-/* --- @share_mkshares@ --- *
- *
- * Arguments: @share *s@ = pointer to share context to fill in
- * @grand *r@ = pointer to random number source
- * @mp *n@ = 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@ must be initialized. If @p@ is zero, a prime
- * number of appropriate size is generated automatically. If
- * @v@ is zero, a vector of appropriate size is allocated. You
- * should use the macro @SHARE_INIT@ or @share_create@ to
- * construct sharing contexts.
- */
-
-extern void share_mkshares(share */*s*/, grand */*r*/, mp */*n*/);
-
-/* --- @share_get@ --- *
- *
- * Arguments: @share *s@ = pointer to share conext
- * @mp *d@ = destination for the share
- * @unsigned x@ = share index to fetch
- *
- * Returns: The share, as requested.
- *
- * Use: Extracts a share from the system. You may extract @MPW_MAX@
- * shares, or @s->p@ shares from the system, whichever is
- * smaller. Shares are indexed from 0.
- */
-
-extern mp *share_get(share */*s*/, mp */*d*/, unsigned /*x*/);
-
-/* --- @share_addedp@ --- *
- *
- * Arguments: @share *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 share_addedp(share */*s*/, unsigned /*x*/);
-
-/* --- @share_add@ --- *
- *
- * Arguments: @share *s@ = pointer to sharing context
- * @unsigned x@ = which share number this is
- * @mp *y@ = the share value
- *
- * Returns: Number of shares required before recovery may be performed.
- *
- * Use: Adds a share to the context. The context must have been
- * initialized with the correct prime @p@ and threshold @t@.
- */
-
-extern unsigned share_add(share */*s*/, unsigned /*x*/, mp */*y*/);
-
-/* --- @share_combine@ --- *
- *
- * Arguments: @share *s@ = pointer to share context
- *
- * Returns: The secret, as a multiprecision integer.
- *
- * Use: Reconstructs a secret, given enough shares.
- */
-
-extern mp *share_combine(share */*s*/);
-
-/*----- That's all, folks -------------------------------------------------*/
-
-#ifdef __cplusplus
- }
-#endif
-
-#endif
projects / u / mdw / catacomb / blobdiff