diff --git a/README.md b/README.md
index 1900005..b138995 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,8 @@
 
 This action is to compute the SHA256 hash of specified files.
 
+The hash function is based on [nektos/act](https://github.com/nektos/act/blob/ac5dd8feb876d37ae483376a137c57383577dace/pkg/exprparser/functions.go#L183). Thanks!
+
 **NOTE:** This action is written in Go. Please setup the Go environment before running this action or use a runner with Go environment installed.
 
 ## Usage