From: frantz@netcom.com (Bill Frantz)
Date: Thu, 10 Oct 1996 11:39:43 -0700 (PDT)
To: "Timothy C. May" <cypherpunks@toad.com
Subject: Re: "Forward Privacy" for ISPs and Customers
Message-ID: <199610101839.LAA14097@netcom8.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


At 10:13 AM 10/9/96 -0800, Timothy C. May wrote:
>Something ISPs could do--and may do if there is sufficient customer
>pressure--is to adopt a policy of "forward secrecy" (to slightly abuse this
>technical term). That is, to have an explicit policy--implemented in the
>software--of _really_ deleting the back messages once a customer downloads
>them to his site. This means that _backups_ must be done in a careful
>manner, such that even the backup tapes or disks are affected by a removal.

One technical approach is described in:

"A Revocable Backup System", dabo@cs.princeton.edu (Dan Boneh) and
rjl@cs.princeton.edu (Richard J. Lipton) in The 6th USENIX Security
Symposium Proceedings.

Basically the idea is to encrypt the file on the backup (tape) and then
lose the encryption key when you want to "forget" the file.


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