diff --git a/library/md4.c b/library/md4.c
index 73cfbf8..3694899 100644
--- a/library/md4.c
+++ b/library/md4.c
@@ -35,7 +35,6 @@
 
 #include "polarssl/md4.h"
 
-#include <string.h>
 #include <stdio.h>
 
 /*
@@ -181,9 +180,9 @@
 /*
  * MD4 process buffer
  */
-void md4_update( md4_context *ctx, const unsigned char *input, int ilen )
+void md4_update( md4_context *ctx, const unsigned char *input, size_t ilen )
 {
-    int fill;
+    size_t fill;
     unsigned long left;
 
     if( ilen <= 0 )
@@ -192,7 +191,7 @@
     left = ctx->total[0] & 0x3F;
     fill = 64 - left;
 
-    ctx->total[0] += ilen;
+    ctx->total[0] += (unsigned long) ilen;
     ctx->total[0] &= 0xFFFFFFFF;
 
     if( ctx->total[0] < (unsigned long) ilen )
@@ -261,7 +260,7 @@
 /*
  * output = MD4( input buffer )
  */
-void md4( const unsigned char *input, int ilen, unsigned char output[16] )
+void md4( const unsigned char *input, size_t ilen, unsigned char output[16] )
 {
     md4_context ctx;
 
@@ -307,9 +306,9 @@
 /*
  * MD4 HMAC context setup
  */
-void md4_hmac_starts( md4_context *ctx, const unsigned char *key, int keylen )
+void md4_hmac_starts( md4_context *ctx, const unsigned char *key, size_t keylen )
 {
-    int i;
+    size_t i;
     unsigned char sum[16];
 
     if( keylen > 64 )
@@ -337,7 +336,7 @@
 /*
  * MD4 HMAC process buffer
  */
-void md4_hmac_update( md4_context *ctx, const unsigned char *input, int ilen )
+void md4_hmac_update( md4_context *ctx, const unsigned char *input, size_t ilen )
 {
     md4_update( ctx, input, ilen );
 }
@@ -370,8 +369,8 @@
 /*
  * output = HMAC-MD4( hmac key, input buffer )
  */
-void md4_hmac( const unsigned char *key, int keylen,
-               const unsigned char *input, int ilen,
+void md4_hmac( const unsigned char *key, size_t keylen,
+               const unsigned char *input, size_t ilen,
                unsigned char output[16] )
 {
     md4_context ctx;