diff --git a/SM4-with-AESENCLAST.md b/SM4-with-AESENCLAST.md
index a28d5d4..2e2f897 100644
--- a/SM4-with-AESENCLAST.md
+++ b/SM4-with-AESENCLAST.md
@@ -24,6 +24,9 @@ My question is how to generate all (M1, C1, M2, C2)?
 **Evolution path**
 
 sm4_box_aesenclast <-> sm4_box_aesbox_1 <-> sm4_box_aesbox_2 <-> sm4_box_aesbox_3 <-> sm4_box_aesbox_4
+
+**We note that each affine transform can be constructed from XOR of two 4x8-bit table lookups, which we implement with constant time byte shuffle instructions (each 16-entry table is in a single 128-bit register).**
+
 ```
 sm4_box_aesenclast
 	y := mm_and_si128(x, const_0f)