From: wcs@anchor.ho.att.com (Bill_Stewart(HOY002)1305)
Date: Mon, 2 Aug 93 18:21:33 PDT
To: cme@ellisun.sw.stratus.com
Subject: Re:  Encrypted BBS?
Message-ID: <9308021921.AA11320@anchor.ho.att.com>
MIME-Version: 1.0
Content-Type: text


> >	Would it be at all possible, given today's present state of
> >cryptography, to run a bbs in a totally encrypted form?  If so, are there
> >any software packages out there that accomplish this at some level?

You've got to think about what threats you're trying to protect against.

- Confiscated Machine - this can be done today with commercial products, a no-brainer.
	You keep the disk in encrypted form, either using software or 
	a hardware-assist DES board, and it's automatically handled by your
	disk drivers using a boot-time secret-key password.
	Neither your users nor your BBS sofware knows any difference.
	(Obviously you also want to decrypt your backup floppies.)

- Wiretapping - there are tons of possible solutions, at varying amounts of work.
	you can either do this with public or secret-key approaches,
	and you can use a shared secret key, separate secret keys,
	session keys set up using secret or public keys, etc.
	Most of these methods affect the BBS sofware itself,
	though you could use an encrypted telnet or other comm program instead,
	presumably in conjunction with the encrypted disk.

	A solution that requires a little more integration is to have the users 
	upload the files encrypted (using random keys), and upload the
	keys (encrypted) and have the host recrypt them with the readers
	public or private keys, either at upload or download time,
	or perhaps on a batch basis during idle time.
	You could probably adapt PGP to retain the initial key for each file,
	and only re-encrypt the key when a user wants to download it,
	instead of re-encrypting the whole file.

- Untrusted users - if there may be narcs on your box, you've got to give
	the users control over who can access what messages they create.
	If the users trust *you*, you can use some sort of password-based system;
	some existing BBSs presumably provide this, and you can even hack
	Usenet to do it (for non-NNTP use, anyway) using Unix groups;
	this allows groups of users who trust each other but not other users.

- Untrusted Sysadm - if *you* may be a narc :-), your users can include 
	PGP-encrypted messages in their postings, and there's not much
	you can do about it :-)  This somewhat solves the untrusted-user
	problem as well, though it makes the closed user group bit more annoying.

			Bill Stewart