diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index ebc1f8f..909df1d 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -28,6 +28,7 @@
 #define POLARSSL_BIGNUM_H
 
 #include <stdio.h>
+#include <string.h>
 
 #define POLARSSL_ERR_MPI_FILE_IO_ERROR                     0x0002
 #define POLARSSL_ERR_MPI_BAD_INPUT_DATA                    0x0004
@@ -43,13 +44,16 @@
  * Define the base integer type, architecture-wise
  */
 #if defined(POLARSSL_HAVE_INT8)
+typedef signed char t_s_int;
 typedef unsigned char  t_int;
 typedef unsigned short t_dbl;
 #else
 #if defined(POLARSSL_HAVE_INT16)
+typedef signed short t_s_int;
 typedef unsigned short t_int;
 typedef unsigned long  t_dbl;
 #else
+  typedef signed long t_s_int;
   typedef unsigned long t_int;
   #if defined(_MSC_VER) && defined(_M_IX86)
   typedef unsigned __int64 t_dbl;
@@ -73,7 +77,7 @@
 typedef struct
 {
     int s;              /*!<  integer sign      */
-    int n;              /*!<  total # of limbs  */
+    size_t n;           /*!<  total # of limbs  */
     t_int *p;           /*!<  pointer to limbs  */
 }
 mpi;
@@ -101,7 +105,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_grow( mpi *X, int nblimbs );
+int mpi_grow( mpi *X, size_t nblimbs );
 
 /**
  * \brief          Copy the contents of Y into X
@@ -131,28 +135,28 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_lset( mpi *X, int z );
+int mpi_lset( mpi *X, t_s_int z );
 
 /**
  * \brief          Return the number of least significant bits
  *
  * \param X        MPI to use
  */
-int mpi_lsb( const mpi *X );
+size_t mpi_lsb( const mpi *X );
 
 /**
  * \brief          Return the number of most significant bits
  *
  * \param X        MPI to use
  */
-int mpi_msb( const mpi *X );
+size_t mpi_msb( const mpi *X );
 
 /**
  * \brief          Return the total size in bytes
  *
  * \param X        MPI to use
  */
-int mpi_size( const mpi *X );
+size_t mpi_size( const mpi *X );
 
 /**
  * \brief          Import from an ASCII string
@@ -180,7 +184,7 @@
  * \note           Call this function with *slen = 0 to obtain the
  *                 minimum required buffer size in *slen.
  */
-int mpi_write_string( const mpi *X, int radix, char *s, int *slen );
+int mpi_write_string( const mpi *X, int radix, char *s, size_t *slen );
 
 /**
  * \brief          Read X from an opened file
@@ -217,7 +221,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_read_binary( mpi *X, const unsigned char *buf, int buflen );
+int mpi_read_binary( mpi *X, const unsigned char *buf, size_t buflen );
 
 /**
  * \brief          Export X into unsigned binary data, big endian
@@ -229,7 +233,7 @@
  * \return         0 if successful,
  *                 POLARSSL_ERR_MPI_BUFFER_TOO_SMALL if buf isn't large enough
  */
-int mpi_write_binary( const mpi *X, unsigned char *buf, int buflen );
+int mpi_write_binary( const mpi *X, unsigned char *buf, size_t buflen );
 
 /**
  * \brief          Left-shift: X <<= count
@@ -240,7 +244,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_shift_l( mpi *X, int count );
+int mpi_shift_l( mpi *X, size_t count );
 
 /**
  * \brief          Right-shift: X >>= count
@@ -251,7 +255,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_shift_r( mpi *X, int count );
+int mpi_shift_r( mpi *X, size_t count );
 
 /**
  * \brief          Compare unsigned values
@@ -287,7 +291,7 @@
  *                -1 if X is lesser  than z or
  *                 0 if X is equal to z
  */
-int mpi_cmp_int( const mpi *X, int z );
+int mpi_cmp_int( const mpi *X, t_s_int z );
 
 /**
  * \brief          Unsigned addition: X = |A| + |B|
@@ -347,7 +351,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_add_int( mpi *X, const mpi *A, int b );
+int mpi_add_int( mpi *X, const mpi *A, t_s_int b );
 
 /**
  * \brief          Signed substraction: X = A - b
@@ -359,7 +363,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_sub_int( mpi *X, const mpi *A, int b );
+int mpi_sub_int( mpi *X, const mpi *A, t_s_int b );
 
 /**
  * \brief          Baseline multiplication: X = A * B
@@ -385,7 +389,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_mul_int( mpi *X, const mpi *A, t_int b );
+int mpi_mul_int( mpi *X, const mpi *A, t_s_int b );
 
 /**
  * \brief          Division by mpi: A = Q * B + R
@@ -417,7 +421,7 @@
  *
  * \note           Either Q or R can be NULL.
  */
-int mpi_div_int( mpi *Q, mpi *R, const mpi *A, int b );
+int mpi_div_int( mpi *Q, mpi *R, const mpi *A, t_s_int b );
 
 /**
  * \brief          Modulo: R = A mod B
@@ -445,7 +449,7 @@
  *                 POLARSSL_ERR_MPI_DIVISION_BY_ZERO if b == 0,
  *                 POLARSSL_ERR_MPI_NEGATIVE_VALUE if b < 0
  */
-int mpi_mod_int( t_int *r, const mpi *A, int b );
+int mpi_mod_int( t_int *r, const mpi *A, t_s_int b );
 
 /**
  * \brief          Sliding-window exponentiation: X = A^E mod N
@@ -477,7 +481,7 @@
  * \return         0 if successful,
  *                 1 if memory allocation failed
  */
-int mpi_fill_random( mpi *X, int size, int (*f_rng)(void *), void *p_rng );
+int mpi_fill_random( mpi *X, size_t size, int (*f_rng)(void *), void *p_rng );
 
 /**
  * \brief          Greatest common divisor: G = gcd(A, B)
@@ -531,7 +535,7 @@
  *                 1 if memory allocation failed,
  *                 POLARSSL_ERR_MPI_BAD_INPUT_DATA if nbits is < 3
  */
-int mpi_gen_prime( mpi *X, int nbits, int dh_flag,
+int mpi_gen_prime( mpi *X, size_t nbits, int dh_flag,
                    int (*f_rng)(void *), void *p_rng );
 
 /**