This extension makes use of the keyring of the current user. This keyring is normally located in ~./.gnupg/. To specify a custom location, store the path to the keyring in the environment variable GNUPGHOME. See putenv for more information how to do this.
Some functions require the specification of a key. This specification can be anything that refers to an unique key (userid, key-id, fingerprint, ...). This documentation uses the fingerprint in all examples.