diff --git a/include/polarssl/md.h b/include/polarssl/md.h
index 7914d88..94b85c3 100644
--- a/include/polarssl/md.h
+++ b/include/polarssl/md.h
@@ -37,6 +37,10 @@
 #endif
 
 #define POLARSSL_ERR_MD_FEATURE_UNAVAILABLE                -0x5080  /**< The selected feature is not available. */
+#define POLARSSL_ERR_MD_BAD_INPUT_DATA                     -0x5100  /**< Bad input parameters to function. */
+#define POLARSSL_ERR_MD_ALLOC_FAILED                       -0x5180  /**< Failed to allocate memory. */
+#define POLARSSL_ERR_MD_FILE_OPEN_FAILED                   -0x5200  /**< Opening of file failed. */
+#define POLARSSL_ERR_MD_FILE_READ_FAILED                   -0x5280  /**< Failure when reading from file. */
 
 typedef enum {
     POLARSSL_MD_NONE=0,
@@ -166,7 +170,8 @@
  *                 be allocated, and must be freed using md_free_ctx() later.
  * \param md_info  message digest to use.
  *
- * \returns        \c 0 on success, \c 1 on parameter failure, \c 2 if
+ * \returns        \c 0 on success, \c POLARSSL_ERR_MD_BAD_INPUT_DATA on
+ *                 parameter failure, \c POLARSSL_ERR_MD_ALLOC_FAILED if
  *                 allocation of the cipher-specific context failed.
  */
 int md_init_ctx( md_context_t *ctx, const md_info_t *md_info );
@@ -177,7 +182,8 @@
  *
  * \param ctx      Free the message-specific context
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_free_ctx( md_context_t *ctx );
 
@@ -222,7 +228,8 @@
  *
  * \param ctx      generic message digest context.
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_starts( md_context_t *ctx );
 
@@ -233,7 +240,8 @@
  * \param input    buffer holding the  datal
  * \param ilen     length of the input data
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_update( md_context_t *ctx, const unsigned char *input, size_t ilen );
 
@@ -243,7 +251,8 @@
  * \param ctx      Generic message digest context
  * \param output   Generic message digest checksum result
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_finish( md_context_t *ctx, unsigned char *output );
 
@@ -255,7 +264,8 @@
  * \param ilen     length of the input data
  * \param output   Generic message digest checksum result
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md( const md_info_t *md_info, const unsigned char *input, size_t ilen,
         unsigned char *output );
@@ -267,8 +277,9 @@
  * \param path     input file name
  * \param output   generic message digest checksum result
  *
- * \return         0 if successful, 1 if fopen failed,
- *                 2 if fread failed, 3 if md_info was NULL
+ * \return         0 if successful, POLARSSL_ERR_MD_FILE_OPEN_FAILED if fopen
+ *                 failed, POLARSSL_ERR_MD_FILE_READ_FAILED if fread failed,
+ *                 POLARSSL_ERR_MD_BAD_INPUT_DATA if md_info was NULL.
  */
 int md_file( const md_info_t *md_info, const char *path, unsigned char *output );
 
@@ -279,7 +290,8 @@
  * \param key      HMAC secret key
  * \param keylen   length of the HMAC key
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_hmac_starts( md_context_t *ctx, const unsigned char *key, size_t keylen );
 
@@ -290,7 +302,8 @@
  * \param input    buffer holding the  data
  * \param ilen     length of the input data
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_hmac_update( md_context_t *ctx, const unsigned char *input, size_t ilen );
 
@@ -300,7 +313,8 @@
  * \param ctx      HMAC context
  * \param output   Generic HMAC checksum result
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_hmac_finish( md_context_t *ctx, unsigned char *output);
 
@@ -309,7 +323,8 @@
  *
  * \param ctx      HMAC context to be reset
  *
- * \returns        0 on success, 1 if ctx is NULL.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_hmac_reset( md_context_t *ctx );
 
@@ -323,7 +338,8 @@
  * \param ilen     length of the input data
  * \param output   Generic HMAC-result
  *
- * \returns        0 on success, 1 if parameter verification fails.
+ * \returns        0 on success, POLARSSL_ERR_MD_BAD_INPUT_DATA if parameter
+ *                 verification fails.
  */
 int md_hmac( const md_info_t *md_info, const unsigned char *key, size_t keylen,
                 const unsigned char *input, size_t ilen,
diff --git a/library/error.c b/library/error.c
index eb03ce1..c9a48db 100644
--- a/library/error.c
+++ b/library/error.c
@@ -137,6 +137,14 @@
 #if defined(POLARSSL_MD_C)
         if( use_ret == -(POLARSSL_ERR_MD_FEATURE_UNAVAILABLE) )
             snprintf( buf, buflen, "MD - The selected feature is not available" );
+        if( use_ret == -(POLARSSL_ERR_MD_BAD_INPUT_DATA) )
+            snprintf( buf, buflen, "MD - Bad input parameters to function" );
+        if( use_ret == -(POLARSSL_ERR_MD_ALLOC_FAILED) )
+            snprintf( buf, buflen, "MD - Failed to allocate memory" );
+        if( use_ret == -(POLARSSL_ERR_MD_FILE_OPEN_FAILED) )
+            snprintf( buf, buflen, "MD - Opening of file failed" );
+        if( use_ret == -(POLARSSL_ERR_MD_FILE_READ_FAILED) )
+            snprintf( buf, buflen, "MD - Failure when reading from file" );
 #endif /* POLARSSL_MD_C */
 
 #if defined(POLARSSL_PEM_C)
diff --git a/library/md.c b/library/md.c
index cb720bb..51fb82e 100644
--- a/library/md.c
+++ b/library/md.c
@@ -153,13 +153,13 @@
 int md_init_ctx( md_context_t *ctx, const md_info_t *md_info )
 {
     if( md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     if( ctx == NULL || ctx->md_ctx != NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     if( ( ctx->md_ctx = md_info->ctx_alloc_func() ) == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_ALLOC_FAILED;
 
     ctx->md_info = md_info;
 
@@ -171,7 +171,7 @@
 int md_free_ctx( md_context_t *ctx )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->ctx_free_func( ctx->md_ctx );
     ctx->md_ctx = NULL;
@@ -182,7 +182,7 @@
 int md_starts( md_context_t *ctx )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->starts_func( ctx->md_ctx );
 
@@ -192,7 +192,7 @@
 int md_update( md_context_t *ctx, const unsigned char *input, size_t ilen )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->update_func( ctx->md_ctx, input, ilen );
 
@@ -202,7 +202,7 @@
 int md_finish( md_context_t *ctx, unsigned char *output )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->finish_func( ctx->md_ctx, output );
 
@@ -213,7 +213,7 @@
             unsigned char *output )
 {
     if ( md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     md_info->digest_func( input, ilen, output );
 
@@ -222,11 +222,19 @@
 
 int md_file( const md_info_t *md_info, const char *path, unsigned char *output )
 {
+    int ret;
+
     if( md_info == NULL )
-        return 3;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
 #if defined(POLARSSL_FS_IO)
-    return md_info->file_func( path, output );
+    ret = md_info->file_func( path, output );
+    if( ret == 2 )
+        return POLARSSL_ERR_MD_FILE_OPEN_FAILED;
+    if( ret == 3 )
+        return POLARSSL_ERR_MD_FILE_READ_FAILED;
+
+    return ret;
 #else
     ((void) path);
     ((void) output);
@@ -238,7 +246,7 @@
 int md_hmac_starts( md_context_t *ctx, const unsigned char *key, size_t keylen )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->hmac_starts_func( ctx->md_ctx, key, keylen);
 
@@ -248,7 +256,7 @@
 int md_hmac_update( md_context_t *ctx, const unsigned char *input, size_t ilen )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->hmac_update_func( ctx->md_ctx, input, ilen );
 
@@ -258,7 +266,7 @@
 int md_hmac_finish( md_context_t *ctx, unsigned char *output)
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->hmac_finish_func( ctx->md_ctx, output);
 
@@ -268,7 +276,7 @@
 int md_hmac_reset( md_context_t *ctx )
 {
     if( ctx == NULL || ctx->md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     ctx->md_info->hmac_reset_func( ctx->md_ctx);
 
@@ -280,7 +288,7 @@
                 unsigned char *output )
 {
     if( md_info == NULL )
-        return 1;
+        return POLARSSL_ERR_MD_BAD_INPUT_DATA;
 
     md_info->hmac_func( key, keylen, input, ilen, output );