diff --git a/aes/aes.cpp b/aes/aes.cpp
index 669b72e..942f55b 100644
--- a/aes/aes.cpp
+++ b/aes/aes.cpp
@@ -11,6 +11,8 @@ http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
 */
 
 /* AES Constants */
+// AES polynomial
+const uint16_t POLYNOMIAL = 0b100011011;
 
 // forward sbox
 const uint8_t SBOX[256] = {
@@ -103,7 +105,7 @@ uint8_t xtime(uint8_t a) {
     uint8_t mask;
 
     if (a & 0b10000000) {
-        mask = 0x1B;
+        mask = POLYNOMIAL & 0xFF;
     }
     else {
         mask = 0x00;