diff --git a/is-my-code-constant-time?.md b/is-my-code-constant-time?.md
index 361a4b8..ec5055e 100644
--- a/is-my-code-constant-time?.md
+++ b/is-my-code-constant-time?.md
@@ -7,3 +7,9 @@ Non-constant time crypto code is dangerous.
 1. [cmd/compile: use devirtualization in escape analysis](https://github.com/golang/go/issues/33160)
 1. [cmd/compile: inlining after devirtualization](https://github.com/golang/go/issues/52193)
 1. [crypto/elliptic: automatically upgrade CurveParams for known curves and deprecate custom ones](https://github.com/golang/go/issues/34648)
+
+## ECDH & SM2 Key Exchange
+SM2 Key Exchange要去除big.Int依赖，看起来比ECDH困难得多，主要是第三、四和五步。
+
+![image](https://user-images.githubusercontent.com/7235232/184781672-60fe4f00-8bab-42f0-960e-e47eb7d3d72f.png)
+