/* -*-c-*-
*
- * $Id: mpbarrett-mexp.c,v 1.1 2001/06/16 12:58:34 mdw Exp $
+ * $Id: mpbarrett-mexp.c,v 1.2 2004/04/01 12:50:09 mdw Exp $
*
* Multiple simultaneous exponentiations
*
/*----- Revision history --------------------------------------------------*
*
* $Log: mpbarrett-mexp.c,v $
+ * Revision 1.2 2004/04/01 12:50:09 mdw
+ * Add cyclic group abstraction, with test code. Separate off exponentation
+ * functions for better static linking. Fix a buttload of bugs on the way.
+ * Generally ensure that negative exponents do inversion correctly. Add
+ * table of standard prime-field subgroups. (Binary field subgroups are
+ * currently unimplemented but easy to add if anyone ever finds a good one.)
+ *
* Revision 1.1 2001/06/16 12:58:34 mdw
* Added simultaneous exponentiation with Barrett reduction.
*
*
* Arguments: @mpbarrett *mb@ = pointer to Barrett reduction context
* @mp *d@ = fake destination
- * @mp_expfactor *f@ = pointer to array of factors
+ * @const mp_expfactor *f@ = pointer to array of factors
* @size_t n@ = number of factors supplied
*
* Returns: If the bases are %$g_0, g_1, \ldots, g_{n-1}$% and the
* %$g_0^{e_0} g_1^{e_1} \ldots g_{n-1}^{e_{n-1}} \bmod m$%
*/
-mp *mpbarrett_mexp(mpbarrett *mb, mp *d, mp_expfactor *f, size_t n)
+mp *mpbarrett_mexp(mpbarrett *mb, mp *d, const mp_expfactor *f, size_t n)
{
+ mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
mp *a = MP_ONE;
mp *spare;
+ mp *g = MP_NEW;
size_t i;
spare = MP_NEW;
for (i = 0; i < n; i++) {
- if (f[i].exp->f & MP_BURN) {
+ if (f[i].exp->f & MP_BURN)
spare = MP_NEWSEC;
- break;
+ if (!(f[i].exp->f & MP_NEG))
+ ff[i].base = MP_COPY(f[i].base);
+ else {
+ ff[i].base = MP_NEW;
+ mp_gcd(&g, 0, &ff[i].base, mb->m, f[i].base);
+ assert(MP_EQ(g, MP_ONE));
}
+ ff[i].exp = f[i].exp;
}
-
- EXP_SIMUL(a, f, n);
+ mp_drop(g);
+ EXP_SIMUL(a, ff, n);
mp_drop(d);
mp_drop(spare);
+ for (i = 0; i < n; i++)
+ mp_drop(ff[i].base);
+ xfree(ff);
return (a);
}