constant encryped stream

[Michael Shields]

In article <BA3BF0FA.2A037%zenadsl6186 at zen.co.uk>,
Peter Fairbrother <zenadsl6186 at zen.co.uk> wrote:
> Get the "pull" from a "party popper" and wrap it in a dollar bill. Record
> the serial number of the bill (some crypto here maybe). Make it impossible
> to open the closet without setting the "pull" off, ie no trapdoor.
>
> Fairly good tamper-evidence, and the token is hard (and very illegal!) to
> forge.

Most of the security features of a dollar bill are not directed
toward the serial number; they are designed to prevent changing the
denomination, or to increase the cost of creating a real-looking bill
from scratch.  Changing the serial number is likely to be fairly
straightforward.

For this to be secure, you would have to keep the serial number a
secret; and in that case, the paper could be any piece of paper with
a secret written on it.

> Depends on your threat model, of course.

But of course.
-- 
Shields.