GPG

Create a key pair.

gpg --gen-key

 List keys.

 gpg --list-keys

Export a public key

 gpg --export UID file.pub

Import a public key 

gpg --import file.pub

Create an encrypted and signed file. 

gpg -se -u "Sender User Name" -r "Receiver User Name" somefile

Decrypt a file. 

gpg -d mydata.tar.gpg