Hi all,
This is a good paper about RFID Blockers that also shows how an RFID
reader selects multiple cards.
http://www.rsasecurity.com/rsalabs/staff/bios/ajuels/publications/blocker/blocker.pdf
Unfortunately, myself I also have lots of collisions already. Even the
Roppongi Hills Entrance card and Roppongi Hills Point Card conflict...
Cheers,
Reto
On Wed, 29 Oct 2003 10:02:37 +0900
Dirk Rösler <lists2003@unicircuits.com> wrote:
> Just speculating...
>
> Chances are it is getting responses from all cards first if they are
> compatible to a certain degree, later discarding invalid ones. If there
> is some challenge-response process going on, the gate may still wait
> for responses of the invalid cards, which they cannot answer correctly,
> thus creating a little delay. Plus I would guess that the medium does
> not allow very fast communication, so you may end up with 1 or 2
> seconds lag until all messages of all cards are communicated, timeouts
> etc., probably serially or even simplex.
>
> Solutions would be to make your card scheme proprietary and not based
> on standards, so only your own cards will work with your readers (I
> believe Sony has made some changes to the standard, not the least to
> provide a "customer lock in" feature but I don't know details). Or
> better, deploy some sort of resolution protocol (e.g. only process data
> from first completed protocol exchange, ignore all other
> communications).
>
> An interesting experiment would be to enter two or more valid cards for
> the system (this case Suica) and see which one is charged and if there
> is lag etc. But there will surely be a resolution protocol.
>
> Otherwise make sure you only present only one card to the reader.
>
> Dirk
>
> On Wednesday, Oct 29, 2003, at 02:09 Asia/Tokyo, Ken Chang wrote:
>
> > does anyone know when you have a number of IC cards within the range,
> > how the technology will guarantee that the station communicate with
> > and only with the wanted one?
> >
> > the JR gates sometimes have problem to access my Suica card, wasting
> > me a second or two when I have other IC cards in the wallet.
> >
> >
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__________________________________________________________
Reto Grob, rgrob@klab.org
Researcher, K Laboratory
Tel: +81-3-5711-1329
Received on Wed Oct 29 03:43:19 2003