Contactless bank cards

Ian Batten igb at
Thu Nov 18 14:51:19 GMT 2010

> If we want to put this into perspective with some real world results there's a paper here <> where a reading range of 25 cm was achieved with USD 110 worth of hardware. This paper is 4 years old and may not even represent the state of the art at the time.

Perhaps not.  But did you notice the slight flaw in using this surreptitiously?  It's in section 2.4:  ``A necessary condition for an increased range is a larger antenna. Theoretical analysis ([Lee03]) shows that for a desired range, r, the optimal antenna diameter is 
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 r. We wanted to demonstrate a reading range of 25-30 cm.''

They used a 39cm diameter copper tube loop to get 25cm.  Assuming that for the attack we're talking about a metre would be a more credible range, you're not going to be inconspicuous with a metre-plus diameter copper loop tucked under your shirt.  Especially as the paper says "We built the loop antenna from 5/16 inch cooking gas copper tube", and even then it wasn't rigid enough: "The tube is tied to a solid non flexible wooden tablet, in order to maintain its shape and to avoid inductance changes under mechanical deformation forces."  


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