Google End-to-End is an open source plugin for Chrome-compatible web browsers that implements OpenPGP in the browser so it can be more easily used by webmail applications like Gmail (shocking!). It isnt available as a plugin to the public yet, so you have to check out the source code and compile it yourself (including working out typos in the instructions and using an old version of Python). There are two ways to use OpenPG PPGP: to sign messages or to encrypt them.”]
Source: https://nakedsecurity.sophos.com/2014/07/01/google-looks-to-make-openpgp-easier-for-gmail-users/