diff --git a/bignum.c b/bignum.c
new file mode 100644
index 0000000000000000000000000000000000000000..a8b2164b7af36f8443e07055e5448a9ef8cbf527
--- /dev/null
+++ b/bignum.c
@@ -0,0 +1,97 @@
+/* bignum.c
+ *
+ * bignum operations that are missing from gmp.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001 Niels Möller
+ *  
+ * The nettle library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ * 
+ * The nettle library 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 Lesser General Public
+ * License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#if HAVE_LIBGMP
+
+#include "bignum.h"
+
+#include <assert.h>
+#include <string.h>
+
+void
+nettle_mpz_get_str_256(unsigned length, uint8_t *s, mpz_t x)
+{
+  uint8_t *dst = s + length - 1;
+  unsigned size = mpz_size(x);
+  unsigned i;
+
+  if (!length)
+    {
+      /* x must be zero */
+      assert(!mpz_sgn(x));
+      return;
+    }
+  
+  assert(mpz_sgn(x) >= 0);
+  assert( (mpz_sizeinbase(x, 2) + 7) / 8 <= length);
+
+  for (i = 0; i<size; i++)
+    {
+      mp_limb_t limb = mpz_getlimbn(x, i);
+      unsigned j;
+
+      for (j = 0; length && j < sizeof(mp_limb_t); j++)
+        {
+          *dst-- = limb & 0xff;
+          limb >>= 8;
+          length--;
+	}
+    }
+  
+  if (length)
+    memset(dst, 0, length);
+}
+
+void
+nettle_mpz_set_str_256(mpz_t x,
+                       unsigned length, const uint8_t *s)
+{
+  size_t i;
+  mpz_t digit;
+
+  mpz_init(digit);
+  mpz_set_ui(x, 0);
+  for (i = 0; i < length; i++)
+    {
+      mpz_set_ui(digit, s[i]);
+      mpz_mul_2exp(digit, digit, (length - i - 1) * 8);
+      mpz_ior(x, x, digit);
+    }
+  mpz_clear(digit);
+}
+
+void
+nettle_mpz_init_set_str_256(mpz_t x,
+                            unsigned length, const uint8_t *s)
+{
+  mpz_init(x);
+  nettle_mpz_set_str_256(x, length, s);
+}
+
+#endif /* HAVE_LIBGMP */
diff --git a/bignum.h b/bignum.h
new file mode 100644
index 0000000000000000000000000000000000000000..244d957331e911ccc208f0ef41349c9df42df720
--- /dev/null
+++ b/bignum.h
@@ -0,0 +1,45 @@
+/* bignum.h
+ *
+ * bignum operations that are missing from gmp.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001 Niels Möller
+ *  
+ * The nettle library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ * 
+ * The nettle library 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 Lesser General Public
+ * License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+ 
+#ifndef NETTLE_BIGNUM_H_INCLUDED
+#define NETTLE_BIGNUM_H_INCLUDED
+
+#include <gmp.h>
+#include <inttypes.h>
+
+/* Writes an unsigned integer as length octets, using big endian byte
+ * order. */
+void
+nettle_mpz_get_str_256(unsigned length, uint8_t *s, mpz_t x);
+
+void
+nettle_mpz_set_str_256(mpz_t x,
+                       unsigned length, const uint8_t *s);
+
+void
+nettle_mpz_init_set_str_256(mpz_t x,
+                            unsigned length, const uint8_t *s);
+
+#endif /* NETTLE_BIGNUM_H_INCLUDED */