How do I disable an RFID tag???

There are tons of different kinds of tags out there. The ones you are working with are read-only, so they cannot be programmed. Even ones that are read/write still have some read-only memory blocks dedicated to storing and reporting a unique ID.

There are a few ways that stores are approaching disabling RFID tags. One is that the entire tag, ID and all, can be over-written, and the unique part of the tag, the part of the ID that is unqiue to that specific tag, is overwritten with a bunch of zeros (00000).

Another way that manufacturers are approaching RFID is to affix the tag to the product in such a way that it can easily be removed after purchase. Sweaters and such include RFID tags that are embedded in a fabric tag that ways "remove before washing or wearing". Even if the customer doesn't remove the tag, it will only survive a few wash cycles before it stops functioning.

What you're talking about is zapping and basically frying the tag. Most tags, especially passive tags like the ones you're using, contain current limitors in them to fend off overly powerful reader fields. Because these tags derive power from the reader's magnetic field, they must control the amount of current that they pull from that field, so they don't burn out if they get too close to a strong reader field.

However, even the best current limitors can be overpowered. Look into building an EMP pulse generator that generates a strong carrier wave at 125KHz, and is attached to an antenna coil which is tuned to 125KHz (or whatever the frequency of the RFID tags you're trying to kill function on). The magnetic field generated by a short the pulse should be strong enough and powerful enough to fry the tag.

Chances are you'll have to place the tag very very close to the pulse antenna coil, and only run the wave generator for a few cycles at 125KHz, otherwise you might fry your antenna.

Hope that helps... and stay away from my implant!


Edited by amal - 23 February 2006 at 11:37am

Hahah.. yeah... I guess so :) I'm not sure if the entire tag is re-writable. I think the tags they are putting in clothing are designed to function somewhat like a UPC code, where part of the stored data works to identify the product type (like a current UPC code), and just the "serial number" or uniquely identifyable portion is read/write... but I could be wrong, the entire tag's memory block may be read/write.

There are tags that you can set a memory block to write-once, read many, where after it's written to that memory block is locked. That's probably how they are approaching it.

Hmm... now i want to run out a get a sweater. I wonder what frequency range they are using... probably 13.56MHz. I'll let you know if I come up with anything!

http://www.tagzapper.com/  -- looks like they haven't figured it out yet either.. or maybe they just don't have it in production.

Here's some info on them:

"US-based West End Laboratories, the research arm of LDC Security, has developed a special RFID tag zapper designed to kill the RFID chip preventing readers from performing unwanted scanning and tracking of people or goods.

According to the company, because information stored on RFID tags can be read by anyone, they may pose privacy threats to customers when deployed in retail environments, and have already triggered a wave of consumer outcry.

“In a naive, RFID-enabled world without technical forethought, there is risk that sensitive information could be visible in secret to anyone with an RFID reader,” said Le Derec Caden, director and chief scientist with West End Laboratories in the US.

“Moreover, the unique serial numbers emitted by RFID tags could be used to track people and objects surreptitiously. For businesses too, RFID introduces new privacy and security risks – and a whole new dimension to corporate espionage. These concerns have motivated our scientists to work on a new generation of technical solutions that match these challenges.”Phil Devenport

Rfid disable: tagzapper!The TagZapper™ is being developed to be a light weight, handheld, device for deactivating RFID transmitting devices. This is intended to fulfill consumer demand for a means to protect their..
"

In order to 'fry' an rfid tag, consider that the antenna coil is of finite length (whatever the length is). Next, consider that for any given 'chip', there IS in fact a max current tolerable. I don't recall other than the datasheet for each chip what that value is.

Now, consider that 125, 134KHz, or whatever, is the ROOT frequency. There are 'octaves' if you will, a doubled freq. ( or x8, x24, etc.) that the RFID's chip will 'sing' or resonate on.

So I guess if you had say 5watts(?) at some EXACT multiple or harmonic(?) that you could couple to the antenna, you could generate enough local near field to fondue the chip in a lcoal cauldron of RF.