/* -*-c-*-
*
- * $Id: mpmont-mexp.c,v 1.7 2002/01/13 13:49:14 mdw Exp $
+ * $Id: mpmont-mexp.c,v 1.8 2004/04/01 12:50:09 mdw Exp $
*
* Multiple simultaneous exponentiations
*
/*----- Revision history --------------------------------------------------*
*
* $Log: mpmont-mexp.c,v $
+ * Revision 1.8 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 1.7 2002/01/13 13:49:14 mdw
* Make @const@-correct.
*
*
* Arguments: @mpmont *mm@ = pointer to Montgomery 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
* except that the %$g_i$% and result are in Montgomery form.
*/
-mp *mpmont_mexpr(mpmont *mm, mp *d, mp_expfactor *f, size_t n)
+static mp *mexpr(mpmont *mm, mp *d, mp_expfactor *f, size_t n)
{
- mp *a = mp_copy(mm->r);
- mp *spare;
+ mp *a = MP_COPY(mm->r);
+ mp *spare = MP_NEW;
+ mp *g = MP_NEW;
size_t i;
- spare = MP_NEW;
for (i = 0; i < n; i++) {
- if (f[i].exp->f & MP_BURN) {
+ mp *t;
+ if (f[i].exp->f & MP_BURN)
spare = MP_NEWSEC;
- break;
+ if (f[i].exp->f & MP_NEG) {
+ t = mpmont_reduce(mm, f[i].base, f[i].base);
+ mp_gcd(&g, 0, &t, mm->m, t);
+ assert(MP_EQ(g, MP_ONE));
+ f[i].base = mpmont_mul(mm, t, t, mm->r2);
}
}
-
+ mp_drop(g);
EXP_SIMUL(a, f, n);
mp_drop(d);
mp_drop(spare);
+ for (i = 0; i < n; i++)
+ MP_DROP(f[i].base);
+ xfree(f);
return (a);
}
+mp *mpmont_mexpr(mpmont *mm, mp *d, const mp_expfactor *f, size_t n)
+{
+ mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
+ size_t i;
+
+ for (i = 0; i < n; i++) {
+ ff[i].base = MP_COPY(f[i].base);
+ ff[i].exp = f[i].exp;
+ }
+ return (mexpr(mm, d, ff, n));
+}
+
/* --- @mpmont_mexp@ --- *
*
* Arguments: @mpmont *mm@ = pointer to Montgomery reduction context
mp *mpmont_mexp(mpmont *mm, mp *d, const mp_expfactor *f, size_t n)
{
- mp_expfactor *v = xmalloc(sizeof(*v) * n);
+ mp_expfactor *ff = xmalloc(n * sizeof(mp_expfactor));
size_t i;
for (i = 0; i < n; i++) {
- v[i].base = mpmont_mul(mm, MP_NEW, f[i].base, mm->r2);
- v[i].exp = f[i].exp;
+ ff[i].base = mpmont_mul(mm, MP_NEW, f[i].base, mm->r2);
+ ff[i].exp = f[i].exp;
}
- d = mpmont_mexpr(mm, d, v, n);
- for (i = 0; i < n; i++)
- MP_DROP(v[i].base);
- xfree(v);
- d = mpmont_reduce(mm, d, d);
- return (d);
+ d = mexpr(mm, d, ff, n);
+ return (mpmont_reduce(mm, d, d));
}
/*----- Test rig ----------------------------------------------------------*/