Need to quickly encrypt a file or an archive? You can do this using the GPG encryption software which is installed by default on many mainstream Linux distributions. To be able to encrypt files with GPG, you have to generate a key pair. To do this, run the following command and follow the on-screen instructions:

gpg --gen-key

When generating the key pair, GPG creates a user ID (UID) to identify your key based on your real name, comments, and email address. You need this UID (or just a part of it like your first name or email address) to specify the key you want to use to encrypt a file:

gpg -e -r part_of_UID file_to_encrypt

For example, if I want to encrypt the TidlyWiki.odt document using my own key, the encrypt command would be as follows:

gpg -e -r Dmitri TiddlyWiki.odt

This command creates an encrypted version of the specified document, and you can recognize it by the .gpg file extension. In this case, the command creates the TiddlyWiki.odt.gpg file. Decrypting an encrypted file is equally easy, and the command that does this looks like this:

gpg -d -o decrypted_file encrypted_file.gpg

For example, to decrypt the TiddlyWiki.odt.gpg, I'd use the following command:

gpg -d -o TiddlyWiki.odt TiddlyWiki.odt.gpg

That's all there is to it. By the way, you can use the gpg --list-keys command to view a list of all the keys on your system. This can come in handy if you don't remember the UID of the key you want to use.