It looks like Den Otter has found the appropriate tools.
One will still limit such a list to a small number of trusted subscribers, because the privacy of PGP-encrypted lists is only as strong as that of the WEAKEST subscriber.
i.e., if one subscriber has a security breach, the entire list traffic is revealed to the intruder.
At 03:38 PM 11/22/99 +0100, you wrote:
>> From: Eliezer S. Yudkowsky <email@example.com>
>> Does anyone know of a mailing-list program that can operate securely in
>> a not-too-inconvenient way? An example might be a mailing list program
>> that can decrypt PGP messages sent to it, re-encrypt the message with
>> the public PGP keys of the recipient list, and send each recipient a
>> message encrypted with vis key.
>Something like this?
>Petidomo supports fully encrypted mailing lists, using the well-known
>encryption programm Pretty Good Privacy (PGP).
>8.2 PGP-encrypted mailing lists at
>"Another very useful feature of the posting filter and the access
>control languange is the ability to maintain encrypted mailing lists.
>The idea is very simple: You create a PGP key pair for your mailing list
>and spread the public key among the subscribers of your mailing list. In
>turn you collect their public keys and store them on the mailing list
>Whenever a subscriber wants to post an article to the mailing list, he
>will encrypt it with the public key of the list server before
>transferring it through the Internet. Petidomo will then receive the
>mail, decrypt and process it and encrypt it again, with the public keys
>of the subscribers. Once encrypted again, the mail is distributed to the
>Please note that at no time the mail was sent through the Internet in
>clear text. Hence this mode is well-suited for maintaining internal
>discussion lists for, say, software development among a few people who
>know each other but live spread throughout the world. Included in the
>distribution are two scripts, pgp-encrypt.sh and pgp-decrypt.sh, which
>realize this. The setup needs a bit of work, but once you understand the
>principle, it is rather easy. Just follow the steps described below".
>Another related link
>"The first thing for you to do is to generate
>another pair of keys - these will be the master keys. Next, send
>copies of both of keys to everyone on the list, using your newfound
>encryption technology. Sending keys in the mail may sound like a
>dangerous idea, but because your friends all have their own sets of
>keys, you can use their personal public keys to encrypt the master keys
>for the list and send the master keys securely to each of the members.
>Now everyone has an identical pair of master keys, and they've never
>even met face to face. These keys are in addition to their own
>personal keys, which they can use for personal encrypted mail.
>Emails sent to the mailing list are encrypted by the public master
>key and broadcast to the list members, who use the private master
>key to decode them. This is a perfect information security system,
>as long as no one's computer gets bagged."
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