OpenPGP.js, the OpenPGP JavaScript Implementation deserves some attention! :-)

OpenPGP.js, OpenPGP JavaScript Implementation: “This project aims to provide an Open Source OpenPGP library in JavaScript so it can be used on virtually every device. Instead of other implementations that are aimed at using native code, OpenPGP.js is meant to bypass this requirement (i.e. people will not have to install gpg on their machines in order to use the library). The idea is to implement all the needed OpenPGP functionality in a JavaScript library that can be reused in other projects that provide browser extensions or server applications.”

This may interest you:   "Zo versleutel je je e-mail met PGP"