Mymail-Crypt is a Chrome browser addon to encrypt messages with GPG operating within Gmail webmail interface, the project aims to be OpenPGP compatible to be able to communicate with anybody using public key encryption even if they have different PGP or GPG software. After installing Mymail-Crypt you will have to generate your encryption keys, this can be done with the addon, entering a password is optional and highly recommended, if you don’t use a password anyone breaking into your Gmail account will be able to decrypt sign and encrypt messages supplanting your identity. Encryption keys can and must be backed up.
Mymail-Crypt is fairly easy to use, you will see a button in Gmail compose screen with the options “Encrypt and sign“, “Encrypt“, “Sign“. Received encrypted Gmail messages can be read using the drop down menu “Decrypt” option and entering your password.
MyMail-Crypt GPG Chrome Gmail
The project uses an OpenPGP open source library called Openpgp.js , it runs locally in JavaScript, messages are encrypted/decrypted in your browser. This addon will stop Google and others from reading your emails during transit but email drafts and decrypted autosaves will be saved in the clear to Gmail servers, encryption only takes places after you click on the “Encrypt” button, it will not protect you while you are composing the message, the developer also warns that it is possible for Gmail to get hold of the encryption password monitoring the user when he types it in.
Another way to encrypt Gmail messages with GPG is using Thunderbird and Enigmail but it won’t work for webmail, or obtaining a digital certificate for your email client.