diff --git a/library/bignum.c b/library/bignum.c
index be4df2fe7..90af7e495 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -59,6 +59,11 @@
 #define mbedtls_free       free
 #endif
 
+#define MPI_VALIDATE_RET( cond )                                       \
+    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_MPI_BAD_INPUT_DATA )
+#define MPI_VALIDATE( cond )                                           \
+    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 #define ciL    (sizeof(mbedtls_mpi_uint))         /* chars in limb  */
 #define biL    (ciL << 3)               /* bits  in limb  */
 #define biH    (ciL << 2)               /* half limb size */
@@ -83,8 +88,7 @@ static void mbedtls_mpi_zeroize( mbedtls_mpi_uint *v, size_t n )
  */
 void mbedtls_mpi_init( mbedtls_mpi *X )
 {
-    if( X == NULL )
-        return;
+    MPI_VALIDATE( X != NULL );
 
     X->s = 1;
     X->n = 0;
@@ -116,6 +120,7 @@ void mbedtls_mpi_free( mbedtls_mpi *X )
 int mbedtls_mpi_grow( mbedtls_mpi *X, size_t nblimbs )
 {
     mbedtls_mpi_uint *p;
+    MPI_VALIDATE_RET( X != NULL );
 
     if( nblimbs > MBEDTLS_MPI_MAX_LIMBS )
         return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
@@ -147,6 +152,10 @@ int mbedtls_mpi_shrink( mbedtls_mpi *X, size_t nblimbs )
 {
     mbedtls_mpi_uint *p;
     size_t i;
+    MPI_VALIDATE_RET( X != NULL );
+
+    if( nblimbs > MBEDTLS_MPI_MAX_LIMBS )
+        return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
 
     /* Actually resize up in this case */
     if( X->n <= nblimbs )
@@ -183,6 +192,8 @@ int mbedtls_mpi_copy( mbedtls_mpi *X, const mbedtls_mpi *Y )
 {
     int ret = 0;
     size_t i;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( Y != NULL );
 
     if( X == Y )
         return( 0 );
@@ -222,6 +233,8 @@ cleanup:
 void mbedtls_mpi_swap( mbedtls_mpi *X, mbedtls_mpi *Y )
 {
     mbedtls_mpi T;
+    MPI_VALIDATE( X != NULL );
+    MPI_VALIDATE( Y != NULL );
 
     memcpy( &T,  X, sizeof( mbedtls_mpi ) );
     memcpy(  X,  Y, sizeof( mbedtls_mpi ) );
@@ -237,6 +250,8 @@ int mbedtls_mpi_safe_cond_assign( mbedtls_mpi *X, const mbedtls_mpi *Y, unsigned
 {
     int ret = 0;
     size_t i;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( Y != NULL );
 
     /* make sure assign is 0 or 1 in a time-constant manner */
     assign = (assign | (unsigned char)-assign) >> 7;
@@ -266,6 +281,8 @@ int mbedtls_mpi_safe_cond_swap( mbedtls_mpi *X, mbedtls_mpi *Y, unsigned char sw
     int ret, s;
     size_t i;
     mbedtls_mpi_uint tmp;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( Y != NULL );
 
     if( X == Y )
         return( 0 );
@@ -298,6 +315,7 @@ cleanup:
 int mbedtls_mpi_lset( mbedtls_mpi *X, mbedtls_mpi_sint z )
 {
     int ret;
+    MPI_VALIDATE_RET( X != NULL );
 
     MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, 1 ) );
     memset( X->p, 0, X->n * ciL );
@@ -315,6 +333,8 @@ cleanup:
  */
 int mbedtls_mpi_get_bit( const mbedtls_mpi *X, size_t pos )
 {
+    MPI_VALIDATE_RET( X != NULL );
+
     if( X->n * biL <= pos )
         return( 0 );
 
@@ -333,6 +353,7 @@ int mbedtls_mpi_set_bit( mbedtls_mpi *X, size_t pos, unsigned char val )
     int ret = 0;
     size_t off = pos / biL;
     size_t idx = pos % biL;
+    MPI_VALIDATE_RET( X != NULL );
 
     if( val != 0 && val != 1 )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
@@ -359,6 +380,7 @@ cleanup:
 size_t mbedtls_mpi_lsb( const mbedtls_mpi *X )
 {
     size_t i, j, count = 0;
+    MPI_VALIDATE_RET( X != NULL );
 
     for( i = 0; i < X->n; i++ )
         for( j = 0; j < biL; j++, count++ )
@@ -439,9 +461,11 @@ int mbedtls_mpi_read_string( mbedtls_mpi *X, int radix, const char *s )
     size_t i, j, slen, n;
     mbedtls_mpi_uint d;
     mbedtls_mpi T;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( s != NULL );
 
     if( radix < 2 || radix > 16 )
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );;
 
     mbedtls_mpi_init( &T );
 
@@ -539,9 +563,12 @@ int mbedtls_mpi_write_string( const mbedtls_mpi *X, int radix,
     size_t n;
     char *p;
     mbedtls_mpi T;
+    MPI_VALIDATE_RET( X    != NULL );
+    MPI_VALIDATE_RET( olen != NULL );
+    MPI_VALIDATE_RET( buflen == 0 || buf != NULL );
 
     if( radix < 2 || radix > 16 )
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );;
 
     n = mbedtls_mpi_bitlen( X );
     if( radix >=  4 ) n >>= 1;
@@ -620,6 +647,12 @@ int mbedtls_mpi_read_file( mbedtls_mpi *X, int radix, FILE *fin )
      */
     char s[ MBEDTLS_MPI_RW_BUFFER_SIZE ];
 
+    MPI_VALIDATE_RET( X   != NULL );
+    MPI_VALIDATE_RET( fin != NULL );
+
+    if( radix < 2 || radix > 16 )
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+
     memset( s, 0, sizeof( s ) );
     if( fgets( s, sizeof( s ) - 1, fin ) == NULL )
         return( MBEDTLS_ERR_MPI_FILE_IO_ERROR );
@@ -651,6 +684,10 @@ int mbedtls_mpi_write_file( const char *p, const mbedtls_mpi *X, int radix, FILE
      * newline characters and '\0'
      */
     char s[ MBEDTLS_MPI_RW_BUFFER_SIZE ];
+    MPI_VALIDATE_RET( X != NULL );
+
+    if( radix < 2 || radix > 16 )
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
     memset( s, 0, sizeof( s ) );
 
@@ -687,6 +724,9 @@ int mbedtls_mpi_read_binary( mbedtls_mpi *X, const unsigned char *buf, size_t bu
     size_t i, j;
     size_t const limbs = CHARS_TO_LIMBS( buflen );
 
+    MPI_VALIDATE_RET( X   != NULL );
+    MPI_VALIDATE_RET( buflen == 0 || buf != NULL );
+
     /* Ensure that target MPI has exactly the necessary number of limbs */
     if( X->n != limbs )
     {
@@ -711,11 +751,16 @@ cleanup:
 int mbedtls_mpi_write_binary( const mbedtls_mpi *X,
                               unsigned char *buf, size_t buflen )
 {
-    size_t stored_bytes = X->n * ciL;
+    size_t stored_bytes;
     size_t bytes_to_copy;
     unsigned char *p;
     size_t i;
 
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( buflen == 0 || buf != NULL );
+
+    stored_bytes = X->n * ciL;
+
     if( stored_bytes < buflen )
     {
         /* There is enough space in the output buffer. Write initial
@@ -754,6 +799,7 @@ int mbedtls_mpi_shift_l( mbedtls_mpi *X, size_t count )
     int ret;
     size_t i, v0, t1;
     mbedtls_mpi_uint r0 = 0, r1;
+    MPI_VALIDATE_RET( X != NULL );
 
     v0 = count / (biL    );
     t1 = count & (biL - 1);
@@ -803,6 +849,7 @@ int mbedtls_mpi_shift_r( mbedtls_mpi *X, size_t count )
 {
     size_t i, v0, v1;
     mbedtls_mpi_uint r0 = 0, r1;
+    MPI_VALIDATE_RET( X != NULL );
 
     v0 = count /  biL;
     v1 = count & (biL - 1);
@@ -845,6 +892,8 @@ int mbedtls_mpi_shift_r( mbedtls_mpi *X, size_t count )
 int mbedtls_mpi_cmp_abs( const mbedtls_mpi *X, const mbedtls_mpi *Y )
 {
     size_t i, j;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( Y != NULL );
 
     for( i = X->n; i > 0; i-- )
         if( X->p[i - 1] != 0 )
@@ -875,6 +924,8 @@ int mbedtls_mpi_cmp_abs( const mbedtls_mpi *X, const mbedtls_mpi *Y )
 int mbedtls_mpi_cmp_mpi( const mbedtls_mpi *X, const mbedtls_mpi *Y )
 {
     size_t i, j;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( Y != NULL );
 
     for( i = X->n; i > 0; i-- )
         if( X->p[i - 1] != 0 )
@@ -909,6 +960,7 @@ int mbedtls_mpi_cmp_int( const mbedtls_mpi *X, mbedtls_mpi_sint z )
 {
     mbedtls_mpi Y;
     mbedtls_mpi_uint p[1];
+    MPI_VALIDATE_RET( X != NULL );
 
     *p  = ( z < 0 ) ? -z : z;
     Y.s = ( z < 0 ) ? -1 : 1;
@@ -926,6 +978,9 @@ int mbedtls_mpi_add_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
     int ret;
     size_t i, j;
     mbedtls_mpi_uint *o, *p, c, tmp;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
     if( X == B )
     {
@@ -1003,6 +1058,9 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
     mbedtls_mpi TB;
     int ret;
     size_t n;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
     if( mbedtls_mpi_cmp_abs( A, B ) < 0 )
         return( MBEDTLS_ERR_MPI_NEGATIVE_VALUE );
@@ -1043,8 +1101,12 @@ cleanup:
  */
 int mbedtls_mpi_add_mpi( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *B )
 {
-    int ret, s = A->s;
+    int ret, s;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
+    s = A->s;
     if( A->s * B->s < 0 )
     {
         if( mbedtls_mpi_cmp_abs( A, B ) >= 0 )
@@ -1074,8 +1136,12 @@ cleanup:
  */
 int mbedtls_mpi_sub_mpi( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *B )
 {
-    int ret, s = A->s;
+    int ret, s;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
+    s = A->s;
     if( A->s * B->s > 0 )
     {
         if( mbedtls_mpi_cmp_abs( A, B ) >= 0 )
@@ -1107,6 +1173,8 @@ int mbedtls_mpi_add_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint
 {
     mbedtls_mpi _B;
     mbedtls_mpi_uint p[1];
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
 
     p[0] = ( b < 0 ) ? -b : b;
     _B.s = ( b < 0 ) ? -1 : 1;
@@ -1123,6 +1191,8 @@ int mbedtls_mpi_sub_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint
 {
     mbedtls_mpi _B;
     mbedtls_mpi_uint p[1];
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
 
     p[0] = ( b < 0 ) ? -b : b;
     _B.s = ( b < 0 ) ? -1 : 1;
@@ -1212,6 +1282,9 @@ int mbedtls_mpi_mul_mpi( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
     int ret;
     size_t i, j;
     mbedtls_mpi TA, TB;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
     mbedtls_mpi_init( &TA ); mbedtls_mpi_init( &TB );
 
@@ -1248,6 +1321,8 @@ int mbedtls_mpi_mul_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_uint
 {
     mbedtls_mpi _B;
     mbedtls_mpi_uint p[1];
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
 
     _B.s = 1;
     _B.n = 1;
@@ -1356,11 +1431,14 @@ static mbedtls_mpi_uint mbedtls_int_div_int( mbedtls_mpi_uint u1,
 /*
  * Division by mbedtls_mpi: A = Q * B + R  (HAC 14.20)
  */
-int mbedtls_mpi_div_mpi( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A, const mbedtls_mpi *B )
+int mbedtls_mpi_div_mpi( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A,
+                         const mbedtls_mpi *B )
 {
     int ret;
     size_t i, n, t, k;
     mbedtls_mpi X, Y, Z, T1, T2;
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
     if( mbedtls_mpi_cmp_int( B, 0 ) == 0 )
         return( MBEDTLS_ERR_MPI_DIVISION_BY_ZERO );
@@ -1471,10 +1549,13 @@ cleanup:
 /*
  * Division by int: A = Q * b + R
  */
-int mbedtls_mpi_div_int( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A, mbedtls_mpi_sint b )
+int mbedtls_mpi_div_int( mbedtls_mpi *Q, mbedtls_mpi *R,
+                         const mbedtls_mpi *A,
+                         mbedtls_mpi_sint b )
 {
     mbedtls_mpi _B;
     mbedtls_mpi_uint p[1];
+    MPI_VALIDATE_RET( A != NULL );
 
     p[0] = ( b < 0 ) ? -b : b;
     _B.s = ( b < 0 ) ? -1 : 1;
@@ -1490,6 +1571,9 @@ int mbedtls_mpi_div_int( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A, m
 int mbedtls_mpi_mod_mpi( mbedtls_mpi *R, const mbedtls_mpi *A, const mbedtls_mpi *B )
 {
     int ret;
+    MPI_VALIDATE_RET( R != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
 
     if( mbedtls_mpi_cmp_int( B, 0 ) < 0 )
         return( MBEDTLS_ERR_MPI_NEGATIVE_VALUE );
@@ -1514,6 +1598,8 @@ int mbedtls_mpi_mod_int( mbedtls_mpi_uint *r, const mbedtls_mpi *A, mbedtls_mpi_
 {
     size_t i;
     mbedtls_mpi_uint x, y, z;
+    MPI_VALIDATE_RET( r != NULL );
+    MPI_VALIDATE_RET( A != NULL );
 
     if( b == 0 )
         return( MBEDTLS_ERR_MPI_DIVISION_BY_ZERO );
@@ -1627,7 +1713,8 @@ static int mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi
 /*
  * Montgomery reduction: A = A * R^-1 mod N
  */
-static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, mbedtls_mpi_uint mm, const mbedtls_mpi *T )
+static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N,
+                        mbedtls_mpi_uint mm, const mbedtls_mpi *T )
 {
     mbedtls_mpi_uint z = 1;
     mbedtls_mpi U;
@@ -1641,7 +1728,9 @@ static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, mbedtls_mpi_uint m
 /*
  * Sliding-window exponentiation: X = A^E mod N  (HAC 14.85)
  */
-int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *E, const mbedtls_mpi *N, mbedtls_mpi *_RR )
+int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A,
+                         const mbedtls_mpi *E, const mbedtls_mpi *N,
+                         mbedtls_mpi *_RR )
 {
     int ret;
     size_t wbits, wsize, one = 1;
@@ -1651,6 +1740,11 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
     mbedtls_mpi RR, T, W[ 2 << MBEDTLS_MPI_WINDOW_SIZE ], Apos;
     int neg;
 
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( E != NULL );
+    MPI_VALIDATE_RET( N != NULL );
+
     if( mbedtls_mpi_cmp_int( N, 0 ) <= 0 || ( N->p[0] & 1 ) == 0 )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
@@ -1855,6 +1949,10 @@ int mbedtls_mpi_gcd( mbedtls_mpi *G, const mbedtls_mpi *A, const mbedtls_mpi *B
     size_t lz, lzt;
     mbedtls_mpi TG, TA, TB;
 
+    MPI_VALIDATE_RET( G != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( B != NULL );
+
     mbedtls_mpi_init( &TG ); mbedtls_mpi_init( &TA ); mbedtls_mpi_init( &TB );
 
     MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &TA, A ) );
@@ -1911,6 +2009,8 @@ int mbedtls_mpi_fill_random( mbedtls_mpi *X, size_t size,
 {
     int ret;
     unsigned char buf[MBEDTLS_MPI_MAX_SIZE];
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( f_rng != NULL );
 
     if( size > MBEDTLS_MPI_MAX_SIZE )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
@@ -1930,6 +2030,9 @@ int mbedtls_mpi_inv_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
 {
     int ret;
     mbedtls_mpi G, TA, TU, U1, U2, TB, TV, V1, V2;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( A != NULL );
+    MPI_VALIDATE_RET( N != NULL );
 
     if( mbedtls_mpi_cmp_int( N, 1 ) <= 0 )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
@@ -2089,7 +2192,11 @@ static int mpi_miller_rabin( const mbedtls_mpi *X, size_t rounds,
     size_t i, j, k, s;
     mbedtls_mpi W, R, T, A, RR;
 
-    mbedtls_mpi_init( &W ); mbedtls_mpi_init( &R ); mbedtls_mpi_init( &T ); mbedtls_mpi_init( &A );
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( f_rng != NULL );
+
+    mbedtls_mpi_init( &W ); mbedtls_mpi_init( &R );
+    mbedtls_mpi_init( &T ); mbedtls_mpi_init( &A );
     mbedtls_mpi_init( &RR );
 
     /*
@@ -2161,7 +2268,8 @@ static int mpi_miller_rabin( const mbedtls_mpi *X, size_t rounds,
     }
 
 cleanup:
-    mbedtls_mpi_free( &W ); mbedtls_mpi_free( &R ); mbedtls_mpi_free( &T ); mbedtls_mpi_free( &A );
+    mbedtls_mpi_free( &W ); mbedtls_mpi_free( &R );
+    mbedtls_mpi_free( &T ); mbedtls_mpi_free( &A );
     mbedtls_mpi_free( &RR );
 
     return( ret );
@@ -2176,6 +2284,8 @@ int mbedtls_mpi_is_prime_ext( const mbedtls_mpi *X, int rounds,
 {
     int ret;
     mbedtls_mpi XX;
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( f_rng != NULL );
 
     XX.s = 1;
     XX.n = X->n;
@@ -2207,12 +2317,15 @@ int mbedtls_mpi_is_prime( const mbedtls_mpi *X,
                   int (*f_rng)(void *, unsigned char *, size_t),
                   void *p_rng )
 {
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( f_rng != NULL );
+
     /*
      * In the past our key generation aimed for an error rate of at most
      * 2^-80. Since this function is deprecated, aim for the same certainty
      * here as well.
      */
-    return mbedtls_mpi_is_prime_ext( X, 40, f_rng, p_rng );
+    return( mbedtls_mpi_is_prime_ext( X, 40, f_rng, p_rng ) );
 }
 #endif
 
@@ -2240,6 +2353,9 @@ int mbedtls_mpi_gen_prime( mbedtls_mpi *X, size_t nbits, int flags,
     mbedtls_mpi_uint r;
     mbedtls_mpi Y;
 
+    MPI_VALIDATE_RET( X != NULL );
+    MPI_VALIDATE_RET( f_rng != NULL );
+
     if( nbits < 3 || nbits > MBEDTLS_MPI_MAX_BITS )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );