diff --git a/lib/mpi/mpi-mul.c b/lib/mpi/mpi-mul.c
new file mode 100644
index 0000000..1f3219e
--- /dev/null
+++ b/lib/mpi/mpi-mul.c
@@ -0,0 +1,194 @@
+/* mpi-mul.c  -  MPI functions
+ *	Copyright (C) 1994, 1996 Free Software Foundation, Inc.
+ *	Copyright (C) 1998, 2001 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ *
+ * Note: This code is heavily based on the GNU MP Library.
+ *	 Actually it's the same code with only minor changes in the
+ *	 way the data is stored; this is to support the abstraction
+ *	 of an optional secure memory allocation which may be used
+ *	 to avoid revealing of sensitive data due to paging etc.
+ *	 The GNU MP Library itself is published under the LGPL;
+ *	 however I decided to publish this code under the plain GPL.
+ */
+
+#include "mpi-internal.h"
+
+int mpi_mul_ui(MPI prod, MPI mult, unsigned long small_mult)
+{
+	mpi_size_t size, prod_size;
+	mpi_ptr_t prod_ptr;
+	mpi_limb_t cy;
+	int sign;
+
+	size = mult->nlimbs;
+	sign = mult->sign;
+
+	if (!size || !small_mult) {
+		prod->nlimbs = 0;
+		prod->sign = 0;
+		return 0;
+	}
+
+	prod_size = size + 1;
+	if (prod->alloced < prod_size)
+		if (mpi_resize(prod, prod_size) < 0)
+			return -ENOMEM;
+	prod_ptr = prod->d;
+
+	cy = mpihelp_mul_1(prod_ptr, mult->d, size, (mpi_limb_t) small_mult);
+	if (cy)
+		prod_ptr[size++] = cy;
+	prod->nlimbs = size;
+	prod->sign = sign;
+	return 0;
+}
+
+int mpi_mul_2exp(MPI w, MPI u, unsigned long cnt)
+{
+	mpi_size_t usize, wsize, limb_cnt;
+	mpi_ptr_t wp;
+	mpi_limb_t wlimb;
+	int usign, wsign;
+
+	usize = u->nlimbs;
+	usign = u->sign;
+
+	if (!usize) {
+		w->nlimbs = 0;
+		w->sign = 0;
+		return 0;
+	}
+
+	limb_cnt = cnt / BITS_PER_MPI_LIMB;
+	wsize = usize + limb_cnt + 1;
+	if (w->alloced < wsize)
+		if (mpi_resize(w, wsize) < 0)
+			return -ENOMEM;
+	wp = w->d;
+	wsize = usize + limb_cnt;
+	wsign = usign;
+
+	cnt %= BITS_PER_MPI_LIMB;
+	if (cnt) {
+		wlimb = mpihelp_lshift(wp + limb_cnt, u->d, usize, cnt);
+		if (wlimb) {
+			wp[wsize] = wlimb;
+			wsize++;
+		}
+	} else {
+		MPN_COPY_DECR(wp + limb_cnt, u->d, usize);
+	}
+
+	/* Zero all whole limbs at low end.  Do it here and not before calling
+	 * mpn_lshift, not to lose for U == W.  */
+	MPN_ZERO(wp, limb_cnt);
+
+	w->nlimbs = wsize;
+	w->sign = wsign;
+	return 0;
+}
+
+int mpi_mul(MPI w, MPI u, MPI v)
+{
+	int rc = -ENOMEM;
+	mpi_size_t usize, vsize, wsize;
+	mpi_ptr_t up, vp, wp;
+	mpi_limb_t cy;
+	int usign, vsign, sign_product;
+	int assign_wp = 0;
+	mpi_ptr_t tmp_limb = NULL;
+
+	if (u->nlimbs < v->nlimbs) {	/* Swap U and V. */
+		usize = v->nlimbs;
+		usign = v->sign;
+		up = v->d;
+		vsize = u->nlimbs;
+		vsign = u->sign;
+		vp = u->d;
+	} else {
+		usize = u->nlimbs;
+		usign = u->sign;
+		up = u->d;
+		vsize = v->nlimbs;
+		vsign = v->sign;
+		vp = v->d;
+	}
+	sign_product = usign ^ vsign;
+	wp = w->d;
+
+	/* Ensure W has space enough to store the result.  */
+	wsize = usize + vsize;
+	if (w->alloced < (size_t) wsize) {
+		if (wp == up || wp == vp) {
+			wp = mpi_alloc_limb_space(wsize);
+			if (!wp)
+				goto nomem;
+			assign_wp = 1;
+		} else {
+			if (mpi_resize(w, wsize) < 0)
+				goto nomem;
+			wp = w->d;
+		}
+	} else {		/* Make U and V not overlap with W.      */
+		if (wp == up) {
+			/* W and U are identical.  Allocate temporary space for U.      */
+			up = tmp_limb = mpi_alloc_limb_space(usize);
+			if (!up)
+				goto nomem;
+			/* Is V identical too?  Keep it identical with U.  */
+			if (wp == vp)
+				vp = up;
+			/* Copy to the temporary space.  */
+			MPN_COPY(up, wp, usize);
+		} else if (wp == vp) {
+			/* W and V are identical.  Allocate temporary space for V.      */
+			vp = tmp_limb = mpi_alloc_limb_space(vsize);
+			if (!vp)
+				goto nomem;
+			/* Copy to the temporary space.  */
+			MPN_COPY(vp, wp, vsize);
+		}
+	}
+
+	if (!vsize)
+		wsize = 0;
+	else {
+		if (mpihelp_mul(wp, up, usize, vp, vsize, &cy) < 0)
+			goto nomem;
+		wsize -= cy ? 0 : 1;
+	}
+
+	if (assign_wp)
+		mpi_assign_limb_space(w, wp, wsize);
+
+	w->nlimbs = wsize;
+	w->sign = sign_product;
+	rc = 0;
+nomem:
+	if (tmp_limb)
+		mpi_free_limb_space(tmp_limb);
+	return rc;
+}
+
+int mpi_mulm(MPI w, MPI u, MPI v, MPI m)
+{
+	if (mpi_mul(w, u, v) < 0)
+		return -ENOMEM;
+	return mpi_fdiv_r(w, w, m);
+}