Maybe you've come across this lately like I have on various websites. Several major news sites now encourage tips through email using an encryption method known as PGP Keys (here's a quick example -- look at the bottom of the article). I didn't really know much about it so I searched online for an explanation and it looks like Computerphile did a rather great explanation of what it is, how it works, and why it's good to use for sensitive information.
The PGP Key has two parts -- a public key and a private key -- and in the simplest terms, the public key is used to encrypt a message and the private key is used to decrypt it. The keys are specific and related to each other and can also be used to verify identity of a sender in circumstances where you cannot do so in any other physical way. Neat!