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| Herbivore: transparent public-key encryption |
Herbivore is an initiative to encourage more people to use encrypted email. Many people are concerned about potential infringements of privacy due to using insecure email, but don't routinely use strong encryption because it is a hassle to set up and use. Furthermore, if I want to send secure email to you, then both of us must use encryption software.
Herbivore aims to reduce this hassle, making strong encryption almost totally effort-free for the user.
Using GnuPG (or equivalent such as PGP) to encrypt your email is useful, if done routinely. If done selectively it is less useful, as an adversary can use traffic analysis to find who you want secret correspondence with. (Here I am considering especially an adversary such as a government with desires to monitor all email - if Herbivore can beat an adversary with such large resources, it will likely provide excellent protection against a weaker adversary).
To make sending encrypted email easier, by getting the email client (Often know as mail user agent or MUA) to do the hard work. Define a standard in email headers for encryption; the purpose of this standard is to allow encrypted emails to be send almost completely automatically if the MUAs at each end support the standard. MUA's that support Herbivore are known as ``Herbivore-aware'' or ``Herbivore-compliant''.
Here's an example, to illustrate how Herbivore will work:
Alice and Bob both use herbivore-compliant MUAs. Alice sends a message to Bob (it's the first time they've emailed each other). The message is sent as plain text, but the herbivore subsystem inserts some extra headers, which say that Alice's MUA is herbivore-aware, and what Alice's public key is.
Bob's MUA reads the email. The Herbivore subsystem in the MUA notes that Alice's email is from a Herbivore-aware client, and remembers Alice's public key.
Bob decides to reply to Alice's message. He composes his reply as normal, and presses SEND. The Herbivore subsystem in Bob's MUA automatically encrypts the email with Alice's public key, before sending it to her.
When Alice's MUA receives the message, it is automatically decoded (using Alice's private key). Alice then sees on her screen the message that Bob sent her.
Compliant MUAs will, by default (overridable by the user) generate a public/private key pair and transmit the public key.
When a compliant MUA sees an incoming email with the headers it makes a note of it. When the user sends an email to that email address, the MUA can encrypt it with the reciever's public key, so that only the receiver can read it.
Compliant MUAs will have a system for checking that the key and fingerprint that are recieved from incoming email are the real keys of the sender, and not altered as part of a man-in-the-middle attack. But the system would default to doing everything automatically (and perhaps telling the user, via a dialog box, what is going on).
As well as defining the headers, a project to implement this scheme would include adding the relevant functionality to one or more of the popular open-source MUAs. Makers of closed source MUAs would be invited to use the protocol too.
About Herbivore:
Some other software projects:
Standards and other links:
By Philip Hunt,
philh@comuno.freeserve.co.uk - your comments are welcome.
Last altered: 8 Feb 2002.