A chrome plugin that enables gpg encryption and decryption for the gmail web interface. Download it from here
A brief tutorial can be found at
We have had users report issues with certain versions of mountain lion. If you encounter any issues please log an issue with as many details as possible to aid us in fixing this.
Encrypting a message : The extension is hopefully easy enough to use , open up a gmail window to begin. To encrypt a new message use the compose button as normal , but you will notice that there is a encrypt link next to the Rich Formatting link.
Clicking the button will encrypt the message that you are typing with the public key for the current recepients. If they are not found in your local pc keyring a error message will be displayed.
If no recepients or message is enterd a error message will be displayed.
Decrypting a message : Start of by clicking a email thread , this will show all mails in that thread. Below each mail in the a Decrypt message link will be shown.
Clicking the link will prompt you for your passphrase with which to decrypt the message, a error will be show if no valid gpg data can be found or if the passphrase is incorrect.
Follow the intrsuction @ https://github.com/RC1140/cr-gpg/wiki/Compiling-extension-manually-(Linux) to build a custom version of the plugin , this is required for linux where various architectures require specific builds.
If you encounter a error or are unable to get the extension to run. Follow the intstructions @ https://github.com/RC1140/cr-gpg/wiki/Debugging which will allow you to find and fix any errors. This also assists when submitting bug requests as it allows the developers to pin point a issue.