diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
new file mode 100644
index 0000000..fe84bb9
--- /dev/null
+++ b/lib/mpi/mpicoder.c
@@ -0,0 +1,365 @@
+/* mpicoder.c  -  Coder for the external representation of MPIs
+ * Copyright (C) 1998, 1999 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
+ */
+
+#include "mpi-internal.h"
+
+#define DIM(v) (sizeof(v)/sizeof((v)[0]))
+#define MAX_EXTERN_MPI_BITS 16384
+
+static uint8_t asn[15] =	/* Object ID is 1.3.14.3.2.26 */
+{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
+	0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
+};
+
+MPI do_encode_md(const void *sha_buffer, unsigned nbits)
+{
+	int nframe = (nbits + 7) / 8;
+	uint8_t *frame, *fr_pt;
+	int i = 0, n;
+	size_t asnlen = DIM(asn);
+	MPI a = MPI_NULL;
+
+	if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)
+		pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",
+		       (int)(SHA1_DIGEST_LENGTH * 8), (int)nbits);
+
+	/* We encode the MD in this way:
+	 *
+	 *       0  A PAD(n bytes)   0  ASN(asnlen bytes)  MD(len bytes)
+	 *
+	 * PAD consists of FF bytes.
+	 */
+	frame = kmalloc(nframe, GFP_KERNEL);
+	if (!frame)
+		return MPI_NULL;
+	n = 0;
+	frame[n++] = 0;
+	frame[n++] = 1;		/* block type */
+	i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3;
+
+	if (i <= 1) {
+		pr_info("MPI: message digest encoding failed\n");
+		kfree(frame);
+		return a;
+	}
+
+	memset(frame + n, 0xff, i);
+	n += i;
+	frame[n++] = 0;
+	memcpy(frame + n, &asn, asnlen);
+	n += asnlen;
+	memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);
+	n += SHA1_DIGEST_LENGTH;
+
+	i = nframe;
+	fr_pt = frame;
+
+	if (n != nframe) {
+		printk
+		    ("MPI: message digest encoding failed, frame length is wrong\n");
+		kfree(frame);
+		return a;
+	}
+
+	a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);
+	mpi_set_buffer(a, frame, nframe, 0);
+	kfree(frame);
+
+	return a;
+}
+
+MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
+{
+	const uint8_t *buffer = xbuffer;
+	int i, j;
+	unsigned nbits, nbytes, nlimbs, nread = 0;
+	mpi_limb_t a;
+	MPI val = MPI_NULL;
+
+	if (*ret_nread < 2)
+		goto leave;
+	nbits = buffer[0] << 8 | buffer[1];
+
+	if (nbits > MAX_EXTERN_MPI_BITS) {
+		pr_info("MPI: mpi too large (%u bits)\n", nbits);
+		goto leave;
+	}
+	buffer += 2;
+	nread = 2;
+
+	nbytes = (nbits + 7) / 8;
+	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+	val = mpi_alloc(nlimbs);
+	if (!val)
+		return MPI_NULL;
+	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+	i %= BYTES_PER_MPI_LIMB;
+	val->nbits = nbits;
+	j = val->nlimbs = nlimbs;
+	val->sign = 0;
+	for (; j > 0; j--) {
+		a = 0;
+		for (; i < BYTES_PER_MPI_LIMB; i++) {
+			if (++nread > *ret_nread) {
+				printk
+				    ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
+				     nread, *ret_nread);
+				goto leave;
+			}
+			a <<= 8;
+			a |= *buffer++;
+		}
+		i = 0;
+		val->d[j - 1] = a;
+	}
+
+leave:
+	*ret_nread = nread;
+	return val;
+}
+EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
+
+/****************
+ * Make an mpi from a character string.
+ */
+int mpi_fromstr(MPI val, const char *str)
+{
+	int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
+	unsigned nbits, nbytes, nlimbs;
+	mpi_limb_t a;
+
+	if (*str == '-') {
+		sign = 1;
+		str++;
+	}
+	if (*str == '0' && str[1] == 'x')
+		hexmode = 1;
+	else
+		return -EINVAL;	/* other bases are not yet supported */
+	str += 2;
+
+	nbits = strlen(str) * 4;
+	if (nbits % 8)
+		prepend_zero = 1;
+	nbytes = (nbits + 7) / 8;
+	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+	if (val->alloced < nlimbs)
+		if (!mpi_resize(val, nlimbs))
+			return -ENOMEM;
+	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+	i %= BYTES_PER_MPI_LIMB;
+	j = val->nlimbs = nlimbs;
+	val->sign = sign;
+	for (; j > 0; j--) {
+		a = 0;
+		for (; i < BYTES_PER_MPI_LIMB; i++) {
+			if (prepend_zero) {
+				c1 = '0';
+				prepend_zero = 0;
+			} else
+				c1 = *str++;
+			assert(c1);
+			c2 = *str++;
+			assert(c2);
+			if (c1 >= '0' && c1 <= '9')
+				c = c1 - '0';
+			else if (c1 >= 'a' && c1 <= 'f')
+				c = c1 - 'a' + 10;
+			else if (c1 >= 'A' && c1 <= 'F')
+				c = c1 - 'A' + 10;
+			else {
+				mpi_clear(val);
+				return 1;
+			}
+			c <<= 4;
+			if (c2 >= '0' && c2 <= '9')
+				c |= c2 - '0';
+			else if (c2 >= 'a' && c2 <= 'f')
+				c |= c2 - 'a' + 10;
+			else if (c2 >= 'A' && c2 <= 'F')
+				c |= c2 - 'A' + 10;
+			else {
+				mpi_clear(val);
+				return 1;
+			}
+			a <<= 8;
+			a |= c;
+		}
+		i = 0;
+
+		val->d[j - 1] = a;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_fromstr);
+
+/****************
+ * Special function to get the low 8 bytes from an mpi.
+ * This can be used as a keyid; KEYID is an 2 element array.
+ * Return the low 4 bytes.
+ */
+u32 mpi_get_keyid(const MPI a, u32 *keyid)
+{
+#if BYTES_PER_MPI_LIMB == 4
+	if (keyid) {
+		keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;
+		keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;
+	}
+	return a->nlimbs >= 1 ? a->d[0] : 0;
+#elif BYTES_PER_MPI_LIMB == 8
+	if (keyid) {
+		keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;
+		keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
+	}
+	return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
+#else
+#error Make this function work with other LIMB sizes
+#endif
+}
+
+/****************
+ * Return an allocated buffer with the MPI (msb first).
+ * NBYTES receives the length of this buffer. Caller must free the
+ * return string (This function does return a 0 byte buffer with NBYTES
+ * set to zero if the value of A is zero. If sign is not NULL, it will
+ * be set to the sign of the A.
+ */
+void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
+{
+	uint8_t *p, *buffer;
+	mpi_limb_t alimb;
+	int i;
+	unsigned int n;
+
+	if (sign)
+		*sign = a->sign;
+	*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
+	if (!n)
+		n++;		/* avoid zero length allocation */
+	p = buffer = kmalloc(n, GFP_KERNEL);
+
+	for (i = a->nlimbs - 1; i >= 0; i--) {
+		alimb = a->d[i];
+#if BYTES_PER_MPI_LIMB == 4
+		*p++ = alimb >> 24;
+		*p++ = alimb >> 16;
+		*p++ = alimb >> 8;
+		*p++ = alimb;
+#elif BYTES_PER_MPI_LIMB == 8
+		*p++ = alimb >> 56;
+		*p++ = alimb >> 48;
+		*p++ = alimb >> 40;
+		*p++ = alimb >> 32;
+		*p++ = alimb >> 24;
+		*p++ = alimb >> 16;
+		*p++ = alimb >> 8;
+		*p++ = alimb;
+#else
+#error please implement for this limb size.
+#endif
+	}
+
+	/* this is sub-optimal but we need to do the shift operation
+	 * because the caller has to free the returned buffer */
+	for (p = buffer; !*p && *nbytes; p++, --*nbytes)
+		;
+	if (p != buffer)
+		memmove(buffer, p, *nbytes);
+
+	return buffer;
+}
+EXPORT_SYMBOL_GPL(mpi_get_buffer);
+
+/****************
+ * Use BUFFER to update MPI.
+ */
+int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
+{
+	const uint8_t *buffer = xbuffer, *p;
+	mpi_limb_t alimb;
+	int nlimbs;
+	int i;
+
+	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+	if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
+		return -ENOMEM;
+	a->sign = sign;
+
+	for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
+#if BYTES_PER_MPI_LIMB == 4
+		alimb = (mpi_limb_t) *p--;
+		alimb |= (mpi_limb_t) *p-- << 8;
+		alimb |= (mpi_limb_t) *p-- << 16;
+		alimb |= (mpi_limb_t) *p-- << 24;
+#elif BYTES_PER_MPI_LIMB == 8
+		alimb = (mpi_limb_t) *p--;
+		alimb |= (mpi_limb_t) *p-- << 8;
+		alimb |= (mpi_limb_t) *p-- << 16;
+		alimb |= (mpi_limb_t) *p-- << 24;
+		alimb |= (mpi_limb_t) *p-- << 32;
+		alimb |= (mpi_limb_t) *p-- << 40;
+		alimb |= (mpi_limb_t) *p-- << 48;
+		alimb |= (mpi_limb_t) *p-- << 56;
+#else
+#error please implement for this limb size.
+#endif
+		a->d[i++] = alimb;
+	}
+	if (p >= buffer) {
+#if BYTES_PER_MPI_LIMB == 4
+		alimb = *p--;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 8;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 16;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 24;
+#elif BYTES_PER_MPI_LIMB == 8
+		alimb = (mpi_limb_t) *p--;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 8;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 16;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 24;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 32;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 40;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 48;
+		if (p >= buffer)
+			alimb |= (mpi_limb_t) *p-- << 56;
+#else
+#error please implement for this limb size.
+#endif
+		a->d[i++] = alimb;
+	}
+	a->nlimbs = i;
+
+	if (i != nlimbs) {
+		pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
+		       nlimbs);
+		BUG();
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_set_buffer);