Husk

Husk is a pass-through solution for automatic OpenPGP encryption.

Husk is an email filter (milter) for MTAs which encrypts emails while they pass through it. It facilitates Web-of-Trust technologies to use decentralized and federated certificate authorities as sources for authenticated OpenPGP certificates. It aims to reduce the amount of administrative effort of obtaining and keeping them up to date by establishing narrow, focused trust delegations. Husk can be used to encrypt emails for services which cannot encrypt on their own – like notification systems or issue trackers, or being used at the end of transport to implement zero-access encryption (for email at rest).

Husk is written in Rust and uses Sequoia PGP for encryption and certificate handling.

Features

• Opportunistic email encryption using OpenPGPv4 or OpenPGPv6 (configurable).
• Integration into the email processing flow via the sendmail-milter protocol.
• Downloading of certificates from online sources on demand.
• Uses the Web-of-Trust by using introducers, allowing a fine grade of trust delegation.
• Periodically update all local certificates by querying online sources (keyservers, etc).
• Optionally tunnel all requests to online sources through the Tor-network.
• Statistics collection.
• Test how Husk will treat email addresses by probing the running process.

Husk allows for a smooth entry. Without introducers and locals (see the documentation for details) Husk will not modify any passing email. This allows you to define introducers and locals step by step and examine their influence on your email traffic. Husk is not an all-or-nothing solution.