Computer Laboratory

Technical reports

The smart card detective: a hand-held EMV interceptor

Omar S. Choudary

December 2012, 55 pages

This technical report is based on a dissertation submitted by the author for the degree of Master of Philosophy (Advanced Computer Science) to the University of Cambridge, Darwin College.


Several vulnerabilities have been found in the EMV system (also known as Chip and PIN). Saar Drimer and Steven Murdoch have successfully implemented a relay attack against EMV using a fake terminal. Recently the same authors have found a method to successfully complete PIN transactions without actually entering the correct PIN. The press has published this vulnerability but they reported such a scenario as being hard to execute in practice because it requires specialized and complex hardware.

As proposed by Ross Anderson and Mike Bond in 2006, I decided to create a miniature man-in-the-middle device to defend smartcard users against relay attacks.

As a result of my MPhil project work I created a hand-held device, called Smart Card Defender (SCD), which intercepts the communication between smartcard and terminal. The device has been built using a low cost ATMEL AT90USB1287 microcontroller and other readily available electronic components. The total cost of the SCD has been around £100, but an industrial version could be produced for less than £20.

I implemented several applications using the SCD, including the defense against the relay attack as well as the recently discovered vulnerability to complete a transaction without using the correct PIN.

All the applications have been successfully tested on CAP readers and live terminals. Furthermore, I have performed real tests using the SCD at several shops in town.

From the experiments using the SCD, I have noticed some particularities of the CAP protocol compared to the EMV standard. I have also discovered that the smartcard does not follow the physical transport protocol exactly. Such findings are presented in detail, along with a discussion of the results.

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BibTeX record

  author =	 {Choudary, Omar S.},
  title = 	 {{The smart card detective: a hand-held EMV interceptor}},
  year = 	 2012,
  month = 	 dec,
  url = 	 {},
  institution =  {University of Cambridge, Computer Laboratory},
  number = 	 {UCAM-CL-TR-827}