There are several tools available for encrypting files under Linux. This article lists the most common alternatives. As of today the GnuPG seems to be the most straightforward choice. Why? Because, chances are, it is already installed on your system (unlike ccrypt), the command line is simple (unlike using openssl directly), it is being very actively developed and is configured to use an up to date cypher (AES256 as of today).
Copy and paste this URL into your WordPress site to embed
Copy and paste this code into your site to embed