/* -*-c-*-
*
- * $Id: share.c,v 1.5 2000/12/06 20:30:10 mdw Exp $
+ * $Id: share.c,v 1.7 2004/04/08 01:36:15 mdw Exp $
*
* Shamir's secret sharing
*
* MA 02111-1307, USA.
*/
-/*----- Revision history --------------------------------------------------*
- *
- * $Log: share.c,v $
- * Revision 1.5 2000/12/06 20:30:10 mdw
- * Change secret sharing interface: present the secret at share
- * construction time.
- *
- * Revision 1.4 2000/10/08 12:16:17 mdw
- * Use @MP_EQ@ instead of @MP_CMP@.
- *
- * Revision 1.3 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 1.2 2000/06/18 23:05:19 mdw
- * Minor performance tweak: use Barrett reduction rather than Montgomery.
- * Fast secret sharing isn't done here, though: see `gfshare' instead.
- *
- * Revision 1.1 2000/06/17 12:09:38 mdw
- * Shamir's secret sharing system.
- *
- */
-
/*----- Header files ------------------------------------------------------*/
#include <stdio.h>
/* --- Dispose of the share vector --- */
if (s->v) {
- for (i = 0; i < s->t; i++) {
- if (s->v[i].y)
- mp_drop(s->v[i].y);
- }
+ for (i = 0; i < s->t; i++)
+ mp_drop(s->v[i].y);
xfree(s->v);
}
/* --- Other stuff --- */
- if (s->p)
- mp_drop(s->p);
+ mp_drop(s->p);
}
/* --- @share_mkshares@ --- *
/* --- Various bits of initialization --- */
mp_build(&u, &uw, &uw + 1);
- if (d)
- mp_drop(d);
+ mp_drop(d);
/* --- Evaluate the polynomial at %$x = i + 1$% --- */
m = mp_sub(m, &ii, &jj);
m = mp_sub(m, s->p, m);
}
- mp_gcd(0, 0, &m, s->p, m);
+ m = mp_modinv(m, m, s->p);
c = mp_mul(c, c, &jj);
c = mpbarrett_reduce(&mb, c, c);
c = mp_mul(c, c, m);
}
a = mpbarrett_reduce(&mb, a, a);
- if (m)
- mp_drop(m);
+ mp_drop(m);
mpbarrett_destroy(&mb);
return (a);
}