Break-Open One-Shot Password Stores

Igor Mozolevsky mozolevsky at
Mon Feb 27 12:10:18 GMT 2012

On 27 February 2012 11:00, Paul Barnfather <lists at> wrote:

> How about the way banks issue PIN codes for ATM and credit cards? They
> come in the form of a printed letter with a neat little plastic
> tear-off tab which makes it very clear if the PIN has been read by
> someone else.
> They seem to be a cheap and effective way of storing and communicating
> a "read once" password.
> I assume they are fairly resistant to casual tampering.
> Does anyone know if they are printed with a conventional printer, or
> do they require specialised hardware to produce?

I would hazard a guess that you can "engineer" the same effect with
carbon paper and a dot-matrix printer (with its ribbon removed), so
long as you don't have needle impressions on the outer layer of the
paper (so you'd probably need to add a layer of paper for padding).

Igor M.

More information about the ukcrypto mailing list