How to Build a Low-Cost, Extended-Range RFID Skimmer

Radio-Frequency Identifier (RFID) technology, using the ISO-14443 standard, is becoming increasingly popular, with applications like credit-cards, national-ID cards, Epassports, and physical access control. The security of such applications is clearly critical. A key feature of RFID-based systems is their very short range: Typical systems are designed to operate at a range of 5-10cm. Despite this very short nominal range, Kfir and Wool predicted that a rogue device can communicate with an ISO-14443 RFID tag from a distance of 40-50cm, based on modeling and simulations. Moreover, they claimed that such a device can be made portable, with low power requirements, and can be built very cheaply. Such a device can be used as a stand-alone RFID skimmer, to surreptitiously read the contents of simple RFID tags. The same device can be as the "leech" part of a relay-attack system, by which an attacker can make purchases using a victim's RFID-enhanced credit card—despite any cryptographic protocols that may be used.

In this study we show that the modeling predictions are quite accurate. We show how to build a portable, extended-range RFID skimmer, using only electronics hobbyist supplies and tools. Our skimmer is able to read ISO-14443 tags from a distance of ≈25cm, uses a lightweight 40cm-diameter copper-tube antenna, is powered by a 12V battery—and requires a budget of ≈$100. We believe that, with some more effort, we can reach ranges of ≈35cm, using the same skills, tools, and budget.

We conclude that (a) ISO-14443 RFID tags can be skimmed from a distance that does not require the attacker to touch the victim; (b) Simple RFID tags, that respond to any reader, are immediately vulnerable to skimming; and (c) We are about half-way toward a full-blown implementation of a relay-attack.