Re: Vanish: Self-destructing digital data

[David Farber <dave () farber net>]

Begin forwarded message:

From: Seth David Schoen <schoen () loyalty org>
Date: July 23, 2009 6:34:30 PM EDT
To: David Farber <dave () farber net>
Cc: Bruce Schechter <bruce () schechter com>
Subject: Re: [IP] Re:   Vanish:  Self-destructing digital data

David Farber writes:

> Begin forwarded message:
>
> From: Bruce Schechter <bruce () schechter com>
> Date: July 23, 2009 5:37:18 PM EDT
> To: David Farber <dave () farber net>
> Subject: RE:   Vanish:  Self-destructing digital data
>
> Hi Dave,
> For IP, if you wish...
> Forgive me if this is a naïve question, but can someone please explain
> the use case where self-destructing data is practical, given that a
> recipient of the data could copy it, save it, take a "screenshot",  
> etc.,
> before the bullet is fired on self-destruction?

These authors specifically noted that:

  Trusted data owners. Users with legitimate access to the same
  VDOs trust each other. [... This] aspect of the threat model is
  straightforward, and in fact is a shared assumption with traditional
  encryption schemes: it would be impossible for our system to protect
  against a user who chooses to leak or permanently preserve the
  cleartext contents of a VDO-encapsulated file through out-of-band
  means. For example, if Ann sends Carla a VDO-encapsulated email, Ann
  must trust Carla not to print and store a hard-copy of the email in
  cleartext.

So this system is meant for the case where the sender and recipient
agree about how long the data should be accessible, and want an
automated way to implement that policy without further human
intervention.  It's not any kind of attempt at a DRM system.

You can compare this to OTR, http://www.cypherpunks.ca/otr/ (great
software which I highly recommend installing in your IM client
right away), where the chat participants agree that they do not
want or need the ability to decrypt the chat after the fact -- but
either of them could save a full unencrypted transcript during the
course of the chat, if they were so inclined.

--
Seth David Schoen <schoen () loyalty org> | Qué empresa fácil no pensar en
    http://www.loyalty.org/~schoen/   | un tigre, reflexioné.
    http://vitanuova.loyalty.org/     |            -- Borges, El Zahir




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