FCrypt

Fcrypt is a browser extension that allows you and a friend or group of friends to safely communicate using the facebook website chat system. All messages and end-to-end encrypted with an AES256 encryption algorithm and encrypted/decrypted locally in the browser so no plaintext ever hits Facebook servers.

Fcrypt automatically encrypts and decrypts messages once a password has been entered so that you can chat naturally with your friends and they can reply like a normal FB conversation.

Please never trust any encryption method with your life. No encryption is perfect, keep this in mind when transmitting sensitive information across the internet and be sure to practise common sense when communicating over any medium.