<br>
<div class="gmail_quote">On 16 November 2010 10:37, Francis Davey <span dir="ltr"><<a href="mailto:fjmd1a@gmail.com">fjmd1a@gmail.com</a>></span> wrote:<br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">Actually my first worry on seeing these things advertised was<br>something entirely legal. Along the lines of an unobtrusive sign<br>
saying "entrance fee £5" or something like that. Auto charge people as<br>they walk in (does contactless have that range? Or will it) and then<br>have plausible deniability for a criminal charge. Obviously some<br>
customers will complain and have a reasonable argument for restitution<br>of the sum taken, but who cares.</blockquote>
<div> </div>
<div>Contactless credit cards are very similar to Oyster cards, and standard</div>
<div>readers have range of 2cm to 5cm or so. The radio power from the reader</div>
<div>is powering the chip in the card. Actually the electric field carries the</div>
<div>power, and as this follows an inverse square rule extending the range</div>
<div>significantly is hard (requiring lots of copper and current).</div>
<div> </div>
<div>The Oyster card equivalents in Japan (Suica for local services in Tokyo)</div>
<div>are also used for small payments at booths and vending machines for</div>
<div>snacks & newspapers. This worked very well when I visited, and in the</div>
<div>nearly 10 years it has been operating I have not heard of any major</div>
<div>fraud incidents.</div>
<div> </div>
<div>Possible defenses include keeping your credit cards in a screened tin</div>
<div>or wallet, or carrying detectors that light a warning LED when a field of</div>
<div>the appropriate frequency is detected.</div>
<div> </div>
<div> </div>
<div>Cheers,</div>
<div>Tony</div></div>