PostGuard addon for Thunderbird

The PostGuard addon utilizes E2E identity-based encryption to secure e-mails. This allows for easy-to-use encryption without the burden of key management.

Anyone can encrypt without prior setup using this system. For decryption, a user requests a decryption key from trusted third party. To do so, the user must authenticate using IRMA, a privacy-friendly decentralized identity platform based on the Idemix protocol. Any combination of attributes in the IRMA ecosystem can be used to encrypt e-mails, which allows for detailed access control over the e-mail's content.

Examples include:

• Sending e-mails to health care professionals, using their professional registration number.
• Sending e-mails to people that can prove that they have a certain role within an organisation.
• Sending e-mails to people that can prove that they are over 18.
• Sending e-mails to people that can prove that they live within a country, city, postal code or street.
• Or any combination of the previous examples.

For more information, see our website and our Github organisation.

Prerequisites

Node and a package manager like yarn, or alternatively npm, are required to build the addon. Building the addon was tested on:

• node v17.9.0,
• yarn v1.22.18.

Building

Install the dependencies and build the extension using:

yarn
yarn build

WebAssembly

Postguard's cryptographic core is implemented in Rust, which is compiled down to WebAssembly in irmaseal-wasm-bindings using wasm-pack. For this purpose, we require a script-source 'unsafe-eval' directive in the Content Security Policy (CSP). Hopefully, this can soon be replaced with unsafe-wasm-eval in a newer version of Firefox/Thunderbird.

Experiments

The addon currently uses four experiments:

• the pg4tb experiment, which has a temporary file API and an experimental way to display messages.
• the switchbar experiment, which is a modification of the notificationbar API that implements a switchable toolbar inside the compose window. This experiment uses innerHTML to adjust the bar. This can probably be avoided, but the input is not user input, rather developer input. For now, no plans are made to publish the experiment, since it is tailored specific to our UX needs.
• the notificationbar API to show warning/error notifications.

Self-distribution & updates

To self-distribute (and update the addon) make sure that the following is present in the manifest:

"browser_specific_settings": {
    "gecko": {
        "update_url": "<UPDATE_URL>/updates.json"
    }
}

At this URL a file (see, dist/updates.json) should be hosted. This file contains updates consisting of a version, a download URL for this specific version and optionally, version restrictions.

{
    "addons": {
        "[email protected]": {
            "updates": [
                {
                    "version": "0.1",
                    "update_link": "<DOWNLOAD_URL>/postguard-tb-addon-0.1.xpi"
                }
            ]
        }
    }
}

A new version can be prepared for auto-updating by bumping the version in the manifest and providing an extra update entry in updates.json. Make sure that both files are publicly available at the URLs mentioned above.

Funding

PostGuard is being developed by a multidisciplinary (cyber security, UX) team from iHub at Radboud University, in the Netherlands, funded by NWO.