diff --git a/is-my-code-constant-time?.md b/is-my-code-constant-time?.md
index 8ebd0c4..2cb9dd8 100644
--- a/is-my-code-constant-time?.md
+++ b/is-my-code-constant-time?.md
@@ -103,4 +103,4 @@ type Curve interface {
 }
 ```
 
-其实，sm2 key exchange和[SEC 1, Version 2.0](https://www.secg.org/sec1-v2.pdf), Section 3.4 Elliptic Curve MQV Primitive 描述的方法一样，只是最后求取shared secret方法不同。
+其实，sm2 key exchange和[SEC 1, Version 2.0](https://www.secg.org/sec1-v2.pdf), Section 3.4 Elliptic Curve MQV Primitive 描述的方法一样，只是最后取shared secret方法不同: MQV和DH一样，都只取X轴值。