OS: SUSE Enterprise Linux 11 SP 3
PHP: 5.3.x
WordPress: 4.4.2
Plugin Version: 0.4.0

I get this error in the logs:

PHP Parse error: syntax error, unexpected '[' in /srv/www/htdocs/wp-content/plugins/wp-pgp-encrypted-emails/class-wp-openpgp.php on line 70