How to use the "keytool -genkeypair" command? I want to generate a pair of public key and private key for myself.

Here is an example of using "keytool -genkeypair" command to generate a pair of public key and private key for yourself:

C:\Users\fyicenter> keytool -genkeypair
-dname CN=www.fyicenter.com -storepass FYIcenter -keypass FYIcenter

What this command did for you:

• Generate a new pair of public key and private key.
• Create a self-signed certificate for the public key.
• Store the certificate and the private together as a new entry in the default keystore file.
• Set the alias name for the new entry as "mykey".
• Set the default keystore file password to "FYIcenter".
• Add a second password "FYIcenter" for the private key.
• Save the default keystore file as ".keystore" in your home folder C:\Users\fyicenter.

If you run the command again, you should get an error, because Keytool can not add another entry with the same alias name "mykey" in the same keystore file.

C:\Users\fyicenter> keytool -genkeypair
-dname CN=www.fyicenter.com -storepass FYIcenter -keypass FYIcenter

keytool error: java.lang.Exception: Key pair not generated, alias <mykey>
already exists

To create another key pair in the same keystore file, use the "-alias" to provide a new name:

C:\Users\fyicenter> keytool -genkeypair
-dname CN=jar.fyicenter.com -storepass FYIcenter -keypass FYIcenter
-alias 2ndkey

⇒ Java "keytool -exportcert" Command Options

⇐ Java "keytool -genkeypair" Command Options

⇑ Managing Certificates with Java Keytool

⇑⇑ Java Keytool: Certificate Management Tool