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A Technical RFID Primer
gManZboy writes "Roy Want, principal engineer at Intel Research, has a pretty meaty technical overview of RFID up at Queue. If you ever wondered how these little things actually work it's worth a read. For instance, I was intrigued to find out how the tags (which are generally battery-free) can absorb enough energy from RFID readers to then power up and transmit their own signal back to the reader."
Are they biodegradable?
vicious, untreated political sewage...niche entertainment for the spiritually unattractive...worshipless pap
I am looking into wiring the office with RFID readers and equipping the engineers with RFID tags that will allow them to beep in and out of the office. Without a valid tag, the doors would not unlock. I've seen this done with smart cards previously, but would like to do it with a more lightweight technology.
The most obvious security risk is that someone steals a tag and enters the premises unnoticed. But there are others that I worry about. Stuff like the ease of replicating an RFID tag or even a hacker passively reading a tag in public then recreating it and gaining access.
I understand the problems many people have with RFID, especially stuff like tracking of purchased items and the like, but I'm more interested in using it for security clearances. Unfortunately, the web is not full of information about this (whereas it is full of information about how RFID is a privacy threat). More information about the practical uses of RFID would be greatly desired.
Tinfoil ON!. Everyone knows they get there energy from stealing your soul a little at a time, sucking the very life essence from your body. Then when they have all your energy they march you into a retirement home which is just a block away from the new universal nutrient - soylent green! Tinfoil OFF!
Mind the gap...
From the article,
In fact, various forms of crude RFID have been used since World War II.
What I think he is refering to but failing to mention by name is the aircraft friend or foe reflector. A tuned cavity was placed on an air craft that would reflect a radar signal many times inside the cavity then emit it back. This delay produced a second reflection to a radar scan. If the shadow image of the plane was on the display, it was a Friend. If it was absent, it was a Foe. It was known as a FOF transponder. (Friend Or Foe)
It has been upgraded to return the plane identification.
The truth shall set you free!
Ooo! A store can track my purchases up to 10 feet beyond their door! Wow! I better call Secret Squirrel for some countermeasure tips!
And of course it had the old idea of an ubergovernment plan of having sensors in every toilet seat and lamp post so that they can track how often I change my underwear.
Honestly, people... The X-Files is over, and our government can't keep Chechnyan rebels from crossing in from Mexico. They can't even prevent the vast waste and fraud perpetrated by the uneducated masses against the various money giveaway programs.
So they're suddenly get their act together and implement a shiny, sparkly supersensor array in order to track which communist manifesto you bought this week down at the Chairman Meow Bookshop/Animal Companion Emporium?
Regardless of how much a retailer's internal facility might disrupt their ability to monitor me, I still plan on getting one of RSA's RFID jammers when they're out.
Huh. Interesting. Do any descendants of P. T. Barnum work at RSA? I think you'd be better served by an orgone energy accumulator.
--- Ban humanity.
For a complete developers guide you can check EM Microelectronic-Marin SA Application Note
However for and introduction, check Wikipedia, or if you just want to start play with it, take a look at some RFID readers.
The passive devices that power up and send back data have nothing on the crystal radios that were used during the 1930's and 1940's. With nothing but an antenna a few feet or yards long,a semiconductor(crystal) and earphones, it was possible to receive enough power to hear radio stations. The so called "Fox Hole Radio" of World War II used a pin made of tin and to contact a "Blue Blade" razor to make the crystal. This simple setup received enough power from the antenna to give audible power to the earphones. I duplicated this years later but used a 1N34 germanium crystal. (And no, you don't need a tuning circuit if you have one strong signal and the others are weak.) The blue blade razors were out of production before I knew that they could be used.
I was intrigued to find out how the tags (which are generally battery-free) can absorb enough energy from RFID readers to then power up and transmit their own signal back to the reader."
The high frequency tags don't actually transmit. They change the impedance of their antenna to modulate the reflection back to the transmitter.
Another problem the article didn't mention is that bags lined with aluminum or copper foil will thwart these systems.
Wansu, th' chinese sailor
The most interesting thing that I learned was that most all RFID tags have a 128 byte "user data" buffer than can be read or written by ANY RFID gate. (Ie: you can put an RFID interface on your laptop and query the tags and change the "user data" portion on them.)
Obviously, this means that any application that is sensitive to tampering should only use the hard-coded serial numbers, not the "user data" area... but history has told us how well people stick to "common sense" security practices in their implementations.
His paper and the Linux tool that allows you to query and change the data are located here: http://www.blackhat.com/html/bh-media-archives/bh- archives-2004.html (scroll down to Lukas Grunwald under "Layer 0".
... used by Exxon (and called Speedpass), I can tell you that they are pretty cool in technology... and yet lame at the same time.
Yes, it is true, there is a blast of energy (usually at a really low wave length - around 100Khz to 180Khz - they aren't very well tuned despite the lit).
For the paranoid, chewing gum wrappers do a good job of blocking them. Actually, a lot of tinted windshields do a good job as well (they tend to contain metal, typically iron from what I am told).
Interference is a big factor with these guys. A noisy engine (spark plugs badly gapped?) can cause problems. But the end result was that the company bought it.
Do I fear the use of it? Not really. But at the same time I don't like them used without my permission. As any device that is used to "track", it needs to have my consent.
That said, they are kinda' cool.
IANAL, but I've seen actors play them on TV