diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
new file mode 100644
index 0000000..ec21412
--- /dev/null
+++ b/include/polarssl/bignum.h
@@ -0,0 +1,406 @@
+/**
+ * \file bignum.h
+ */
+#ifndef XYSSL_BIGNUM_H
+#define XYSSL_BIGNUM_H
+
+#include <stdio.h>
+
+#define XYSSL_ERR_MPI_FILE_IO_ERROR                     -0x0002
+#define XYSSL_ERR_MPI_BAD_INPUT_DATA                    -0x0004
+#define XYSSL_ERR_MPI_INVALID_CHARACTER                 -0x0006
+#define XYSSL_ERR_MPI_BUFFER_TOO_SMALL                  -0x0008
+#define XYSSL_ERR_MPI_NEGATIVE_VALUE                    -0x000A
+#define XYSSL_ERR_MPI_DIVISION_BY_ZERO                  -0x000C
+#define XYSSL_ERR_MPI_NOT_ACCEPTABLE                    -0x000E
+
+#define MPI_CHK(f) if( ( ret = f ) != 0 ) goto cleanup
+
+/*
+ * Define the base integer type, architecture-wise
+ */
+#if defined(XYSSL_HAVE_INT8)
+typedef unsigned char  t_int;
+typedef unsigned short t_dbl;
+#else
+#if defined(XYSSL_HAVE_INT16)
+typedef unsigned short t_int;
+typedef unsigned long  t_dbl;
+#else
+  typedef unsigned long t_int;
+  #if defined(_MSC_VER) && defined(_M_IX86)
+  typedef unsigned __int64 t_dbl;
+  #else
+    #if defined(__amd64__) || defined(__x86_64__)    || \
+        defined(__ppc64__) || defined(__powerpc64__) || \
+        defined(__ia64__)  || defined(__alpha__)
+    typedef unsigned int t_dbl __attribute__((mode(TI)));
+    #else
+    typedef unsigned long long t_dbl;
+    #endif
+  #endif
+#endif
+#endif
+
+/**
+ * \brief          MPI structure
+ */
+typedef struct
+{
+    int s;              /*!<  integer sign      */
+    int n;              /*!<  total # of limbs  */
+    t_int *p;           /*!<  pointer to limbs  */
+}
+mpi;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \brief          Initialize one or more mpi
+ */
+void mpi_init( mpi *X, ... );
+
+/**
+ * \brief          Unallocate one or more mpi
+ */
+void mpi_free( mpi *X, ... );
+
+/**
+ * \brief          Enlarge to the specified number of limbs
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_grow( mpi *X, int nblimbs );
+
+/**
+ * \brief          Copy the contents of Y into X
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_copy( mpi *X, mpi *Y );
+
+/**
+ * \brief          Swap the contents of X and Y
+ */
+void mpi_swap( mpi *X, mpi *Y );
+
+/**
+ * \brief          Set value from integer
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_lset( mpi *X, int z );
+
+/**
+ * \brief          Return the number of least significant bits
+ */
+int mpi_lsb( mpi *X );
+
+/**
+ * \brief          Return the number of most significant bits
+ */
+int mpi_msb( mpi *X );
+
+/**
+ * \brief          Return the total size in bytes
+ */
+int mpi_size( mpi *X );
+
+/**
+ * \brief          Import from an ASCII string
+ *
+ * \param X        destination mpi
+ * \param radix    input numeric base
+ * \param s        null-terminated string buffer
+ *
+ * \return         0 if successful, or an XYSSL_ERR_MPI_XXX error code
+ */
+int mpi_read_string( mpi *X, int radix, char *s );
+
+/**
+ * \brief          Export into an ASCII string
+ *
+ * \param X        source mpi
+ * \param radix    output numeric base
+ * \param s        string buffer
+ * \param slen     string buffer size
+ *
+ * \return         0 if successful, or an XYSSL_ERR_MPI_XXX error code
+ *
+ * \note           Call this function with *slen = 0 to obtain the
+ *                 minimum required buffer size in *slen.
+ */
+int mpi_write_string( mpi *X, int radix, char *s, int *slen );
+
+/**
+ * \brief          Read X from an opened file
+ *
+ * \param X        destination mpi
+ * \param radix    input numeric base
+ * \param fin      input file handle
+ *
+ * \return         0 if successful, or an XYSSL_ERR_MPI_XXX error code
+ */
+int mpi_read_file( mpi *X, int radix, FILE *fin );
+
+/**
+ * \brief          Write X into an opened file, or stdout
+ *
+ * \param p        prefix, can be NULL
+ * \param X        source mpi
+ * \param radix    output numeric base
+ * \param fout     output file handle
+ *
+ * \return         0 if successful, or an XYSSL_ERR_MPI_XXX error code
+ *
+ * \note           Set fout == NULL to print X on the console.
+ */
+int mpi_write_file( char *p, mpi *X, int radix, FILE *fout );
+
+/**
+ * \brief          Import X from unsigned binary data, big endian
+ *
+ * \param X        destination mpi
+ * \param buf      input buffer
+ * \param buflen   input buffer size
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_read_binary( mpi *X, unsigned char *buf, int buflen );
+
+/**
+ * \brief          Export X into unsigned binary data, big endian
+ *
+ * \param X        source mpi
+ * \param buf      output buffer
+ * \param buflen   output buffer size
+ *
+ * \return         0 if successful,
+ *                 XYSSL_ERR_MPI_BUFFER_TOO_SMALL if buf isn't large enough
+ *
+ * \note           Call this function with *buflen = 0 to obtain the
+ *                 minimum required buffer size in *buflen.
+ */
+int mpi_write_binary( mpi *X, unsigned char *buf, int buflen );
+
+/**
+ * \brief          Left-shift: X <<= count
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_shift_l( mpi *X, int count );
+
+/**
+ * \brief          Right-shift: X >>= count
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_shift_r( mpi *X, int count );
+
+/**
+ * \brief          Compare unsigned values
+ *
+ * \return         1 if |X| is greater than |Y|,
+ *                -1 if |X| is lesser  than |Y| or
+ *                 0 if |X| is equal to |Y|
+ */
+int mpi_cmp_abs( mpi *X, mpi *Y );
+
+/**
+ * \brief          Compare signed values
+ *
+ * \return         1 if X is greater than Y,
+ *                -1 if X is lesser  than Y or
+ *                 0 if X is equal to Y
+ */
+int mpi_cmp_mpi( mpi *X, mpi *Y );
+
+/**
+ * \brief          Compare signed values
+ *
+ * \return         1 if X is greater than z,
+ *                -1 if X is lesser  than z or
+ *                 0 if X is equal to z
+ */
+int mpi_cmp_int( mpi *X, int z );
+
+/**
+ * \brief          Unsigned addition: X = |A| + |B|
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_add_abs( mpi *X, mpi *A, mpi *B );
+
+/**
+ * \brief          Unsigned substraction: X = |A| - |B|
+ *
+ * \return         0 if successful,
+ *                 XYSSL_ERR_MPI_NEGATIVE_VALUE if B is greater than A
+ */
+int mpi_sub_abs( mpi *X, mpi *A, mpi *B );
+
+/**
+ * \brief          Signed addition: X = A + B
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_add_mpi( mpi *X, mpi *A, mpi *B );
+
+/**
+ * \brief          Signed substraction: X = A - B
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_sub_mpi( mpi *X, mpi *A, mpi *B );
+
+/**
+ * \brief          Signed addition: X = A + b
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_add_int( mpi *X, mpi *A, int b );
+
+/**
+ * \brief          Signed substraction: X = A - b
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_sub_int( mpi *X, mpi *A, int b );
+
+/**
+ * \brief          Baseline multiplication: X = A * B
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_mul_mpi( mpi *X, mpi *A, mpi *B );
+
+/**
+ * \brief          Baseline multiplication: X = A * b
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_mul_int( mpi *X, mpi *A, t_int b );
+
+/**
+ * \brief          Division by mpi: A = Q * B + R
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_DIVISION_BY_ZERO if B == 0
+ *
+ * \note           Either Q or R can be NULL.
+ */
+int mpi_div_mpi( mpi *Q, mpi *R, mpi *A, mpi *B );
+
+/**
+ * \brief          Division by int: A = Q * b + R
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_DIVISION_BY_ZERO if b == 0
+ *
+ * \note           Either Q or R can be NULL.
+ */
+int mpi_div_int( mpi *Q, mpi *R, mpi *A, int b );
+
+/**
+ * \brief          Modulo: R = A mod B
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_DIVISION_BY_ZERO if B == 0
+ */
+int mpi_mod_mpi( mpi *R, mpi *A, mpi *B );
+
+/**
+ * \brief          Modulo: r = A mod b
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_DIVISION_BY_ZERO if b == 0
+ */
+int mpi_mod_int( t_int *r, mpi *A, int b );
+
+/**
+ * \brief          Sliding-window exponentiation: X = A^E mod N
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_BAD_INPUT_DATA if N is negative or even
+ *
+ * \note           _RR is used to avoid re-computing R*R mod N across
+ *                 multiple calls, which speeds up things a bit. It can
+ *                 be set to NULL if the extra performance is unneeded.
+ */
+int mpi_exp_mod( mpi *X, mpi *A, mpi *E, mpi *N, mpi *_RR );
+
+/**
+ * \brief          Greatest common divisor: G = gcd(A, B)
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed
+ */
+int mpi_gcd( mpi *G, mpi *A, mpi *B );
+
+/**
+ * \brief          Modular inverse: X = A^-1 mod N
+ *
+ * \return         0 if successful,
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_BAD_INPUT_DATA if N is negative or nil
+ *                 XYSSL_ERR_MPI_NOT_ACCEPTABLE if A has no inverse mod N
+ */
+int mpi_inv_mod( mpi *X, mpi *A, mpi *N );
+
+/**
+ * \brief          Miller-Rabin primality test
+ *
+ * \return         0 if successful (probably prime),
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_NOT_ACCEPTABLE if X is not prime
+ */
+int mpi_is_prime( mpi *X, int (*f_rng)(void *), void *p_rng );
+
+/**
+ * \brief          Prime number generation
+ *
+ * \param X        destination mpi
+ * \param nbits    required size of X in bits
+ * \param dh_flag  if 1, then (X-1)/2 will be prime too
+ * \param f_rng    RNG function
+ * \param p_rng    RNG parameter
+ *
+ * \return         0 if successful (probably prime),
+ *                 1 if memory allocation failed,
+ *                 XYSSL_ERR_MPI_BAD_INPUT_DATA if nbits is < 3
+ */
+int mpi_gen_prime( mpi *X, int nbits, int dh_flag,
+                   int (*f_rng)(void *), void *p_rng );
+
+/**
+ * \brief          Checkup routine
+ *
+ * \return         0 if successful, or 1 if the test failed
+ */
+int mpi_self_test( int verbose );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* bignum.h */