diff --git a/library/aria.c b/library/aria.c
index 924f952..a1876b7 100644
--- a/library/aria.c
+++ b/library/aria.c
@@ -588,7 +588,6 @@
                             const unsigned char *input,
                             unsigned char *output )
 {
-    int i;
     unsigned char temp[MBEDTLS_ARIA_BLOCKSIZE];
 
     ARIA_VALIDATE_RET( ctx != NULL );
@@ -608,8 +607,7 @@
             memcpy( temp, input, MBEDTLS_ARIA_BLOCKSIZE );
             mbedtls_aria_crypt_ecb( ctx, input, output );
 
-            for( i = 0; i < MBEDTLS_ARIA_BLOCKSIZE; i++ )
-                output[i] = (unsigned char)( output[i] ^ iv[i] );
+            mbedtls_xor( output, output, iv, MBEDTLS_ARIA_BLOCKSIZE );
 
             memcpy( iv, temp, MBEDTLS_ARIA_BLOCKSIZE );
 
@@ -622,8 +620,7 @@
     {
         while( length > 0 )
         {
-            for( i = 0; i < MBEDTLS_ARIA_BLOCKSIZE; i++ )
-                output[i] = (unsigned char)( input[i] ^ iv[i] );
+            mbedtls_xor( output, input, iv, MBEDTLS_ARIA_BLOCKSIZE );
 
             mbedtls_aria_crypt_ecb( ctx, output, output );
             memcpy( iv, output, MBEDTLS_ARIA_BLOCKSIZE );