Update README.md

README.md

@@ -33,7 +33,31 @@ For a detailed explanation of the underlying theory and security proofs, please
 ![348681154-37b88d3c-9bd6-4436-9837-1a0b078e5ac1](https://github.com/user-attachments/assets/8bd6fd28-b7be-4c0e-b417-7ab5e95b13bc)
 
 
-## Installation
+## Installlation
+```console
+$ go install github.com/xtaci/hppk/cmd/hppktool
+$ ./hppktool
+HPPK key management tool.
+Supports key generation, signing, verification, and secret encryption.
+
+Usage:
+  hppktool [command]
+
+Available Commands:
+  completion  Generate the autocompletion script for the specified shell
+  encrypt     Encrypts a message from standard input
+  help        Help about any command
+  keygen      Generate an HPPK private/public key pair
+  sign        Sign a message from standard input
+  verify      Verify a message from standard input
+
+Flags:
+  -h, --help     help for hppktool
+  -s, --silent   Suppress non-essential messages
+
+Use "hppktool [command] --help" for more information about a command.
+```
+## Using Library
 
 To use HPPK, you need to have Go installed. You can download and install Go from [the official website](https://golang.org/dl/).