PGP for WhatsApp used openpgp.js to provide a second layer of end-to-end encryption. https://github.com/openpgpjs/openpgpjs/blob/master/README.md

Users must use https://web.whatsapp.com/ to make full use of the extension. However, users can encrypt and decrypt messages using their own PGP client and then send messages and share keys over WhatsApp. The recipient can then make use of this extension to read and respond.

Available from the chrome store at https://chrome.google.com/webstore/detail/pgp-for-whatsapp/acfnffcajlhbanaaaompjnojnmacefck or add to browser manually.

Extension Requirements

• The extension must not make calls to external endpoints.

Todo

• Add background worker thread for crypto functions.
• Refactor and fully document.