diff --git a/programs/aes/crypt_and_hash.c b/programs/aes/crypt_and_hash.c
index 5ed2ece..9ff5351 100644
--- a/programs/aes/crypt_and_hash.c
+++ b/programs/aes/crypt_and_hash.c
@@ -277,10 +277,27 @@
 
         p = argv[2];
 
-        mbedtls_md_starts( &md_ctx );
-        mbedtls_md_update( &md_ctx, buffer, 8 );
-        mbedtls_md_update( &md_ctx, (unsigned char *) p, strlen( p ) );
-        mbedtls_md_finish( &md_ctx, digest );
+        if( mbedtls_md_starts( &md_ctx ) != 0 )
+        {
+            mbedtls_fprintf( stderr, "mbedtls_md_starts() returned error\n" );
+            goto exit;
+        }
+        if( mbedtls_md_update( &md_ctx, buffer, 8 ) != 0 )
+        {
+            mbedtls_fprintf( stderr, "mbedtls_md_update() returned error\n" );
+            goto exit;
+        }
+        if( mbedtls_md_update( &md_ctx, ( unsigned char * ) p, strlen( p ) )
+            != 0 )
+        {
+            mbedtls_fprintf( stderr, "mbedtls_md_update() returned error\n" );
+            goto exit;
+        }
+        if( mbedtls_md_finish( &md_ctx, digest ) != 0 )
+        {
+            mbedtls_fprintf( stderr, "mbedtls_md_finish() returned error\n" );
+            goto exit;
+        }
 
         memcpy( IV, digest, 16 );
 
@@ -302,10 +319,30 @@
 
         for( i = 0; i < 8192; i++ )
         {
-            mbedtls_md_starts( &md_ctx );
-            mbedtls_md_update( &md_ctx, digest, 32 );
-            mbedtls_md_update( &md_ctx, key, keylen );
-            mbedtls_md_finish( &md_ctx, digest );
+            if( mbedtls_md_starts( &md_ctx ) != 0 )
+            {
+                mbedtls_fprintf( stderr,
+                                 "mbedtls_md_starts() returned error\n" );
+                goto exit;
+            }
+            if( mbedtls_md_update( &md_ctx, digest, 32 ) != 0 )
+            {
+                mbedtls_fprintf( stderr,
+                                 "mbedtls_md_update() returned error\n" );
+                goto exit;
+            }
+            if( mbedtls_md_update( &md_ctx, key, keylen ) != 0 )
+            {
+                mbedtls_fprintf( stderr,
+                                 "mbedtls_md_update() returned error\n" );
+                goto exit;
+            }
+            if( mbedtls_md_finish( &md_ctx, digest ) != 0 )
+            {
+                mbedtls_fprintf( stderr,
+                                 "mbedtls_md_finish() returned error\n" );
+                goto exit;
+            }
 
         }