From: Mike Ingle <MIKEINGLE@delphi.com>
Date: Thu, 30 Dec 93 23:30:43 PST
To: cypherpunks@toad.com
Subject: Anonymous Video on Demand
Message-ID: <01H743A34VWI93AD45@delphi.com>
MIME-Version: 1.0
Content-Type: text/plain


>Does anyone know of a good, practical way of doing "video on demand" in  
>such a way that the video supplier can't track the videos you select?

Are you thinking of physical videotape or electronic distribution?

For electronic distribution, suppose you have a fiber-optic cable with
n channels, where n is a large number. You send in your request and pay
with digicash or a prepaid system like a prepaid phone card. You send
them an encryption key, and they broadcast the movie over one of the
channels. Or they generate the encryption key and send it to you using
a key you gave them. Problem: you can share the encryption key with
a few thousand of your closest friends, thus cheating the video dealer.
They could require you to make a digicash deposit, and offer a reward
for anyone who reports a pirated encryption key. If you give out the key,
someone reports it and gets half your deposit, and they keep the rest.
But a group of people who all trust each other could still rip off
the video dealer. You could have a decoder with a key unknown to you,
but that system would be only as strong as the physical security
of the decoder. 

Is there any way to use offline-digicash-like techniques to set up
a system so that if you reveal the encryption key, you also reveal
your identity? This would be a real deterrent.

For a videotape system, there is no strong way I can think of to prevent
revealing your identity. You have to pick up the tape, and they have to
know what to record on it or which tape to put out. A camera at the site
could always catch you in the act of retrieving the tape.

It is possible to protect the dealer in an anonymous transaction,
but not the customer. The dealer, if he was selling pirate tapes,
could go out and hide them in various places. In exchange for your
digicash, he tells you where one is.

--- Mike