If dealing with encryption especially with GPG keys on several hosts it might be a good idea to use different passphrases for a secret secret key. If it is a good idea or not to use different passphrases the answer to this question is not easy and it depends on the situation and the security policies one needs to follow.

Here a short write-up how to change a GPG secret key passphrase:

List GPG available keys in your ~ home directory:

gpg --list-keys

After getting an overview of available keys choose the GPG key you want to alter:

shell % gpg --edit-key <My GPG key>

While using the GPG version 2 the command line interface will only accept the long form of the GPG key. The key will not be recognized or chosen if the short form is used.

Changing the GPG key passphrase:

gpg > passwd

Saving the changed result:

gpg > save