You can get a functional, assembled RFID reader from Parallax for $40. You would need a uC capable of generating the 125 KHz while simultaneously monitoring the power going into the LC antenna circuit and decoding any changes that would indicate the presence of a second tuned or detuned circuit drawing power off it. It’s quite a bit more complicated than emulating the card, which was designed to be simple and dirt cheap and not really worth the effort when a turnkey solution is available.

This card hack is kind of cool mainly because there is no pretense of it being practical, and you could theoretically use it to clone a card, which with the read only cards is generally assumed to be impossible.

I’m not proficient with RFID as in, I’ve never done any work with them personally, but I understand their basic function and use. But would it be possible to brute force copies of “read only” cards? Obviously this would be a slow and tedious process, much like any form of brute force hack. But, just to enlighten me, the idea of brute force hacking RFID is still a “possibility”, correct? Would a “rainbow table-esque” be a “feasible” project? I have zero intention, but, as any hacker, i’m just trying to broaden my knowledge.

Not only does Parallax have an RFID unit ready for sale, the following thread on their forums is a very nice DIY implementation:

http://forums.parallax.com/forums/default.aspx?f=25&m=287204

An $8 Propeller plus some junkbox parts = win.

How ironic then that this is an entry on instructables.com, the site that turned so repressive and no doubt would see us all tagged.

Nothing about 13.56Mz cards?
they have more feature (internal memory, password protection, sectors, anti-collision).
I’m trying to inteface my arduino to serial reader, but i’m also interested to make a spoofer..

@skinner
As klulukasz said there are a ton of possible combinations and it would take a long time to go through them all. I’ve heard though that some companies buy batch of cards that end up being sequential. If that’s the case, then if you can just read one card from a location, then you could work from there. In many cases if you have one working ID (the one you were able to read) you don’t need any more, but in other cases different cards give access to different locations. So, if your ID doesn’t work for a door, you could try several IDs around the one you’re using.

@Lorenzo
I’m not sure an Arduino is fast enough to emulate a 13.56Mhz card (it’s about100 times faster). I’m curios if this could be done with a Maple (Arduino clone using an ARM processor) or with a Butterly Uno (FPGA that you can program using the Arudino stuff). I’m guessing you could do something similar to the 125KHz one, I’m going to try it with my Maple and see how it goes.

I’d love to see a cheap DIY reader. The Propeller one is really cool. It would be awesome to combine that reader with this emulator. It would be even cooler if you could do it the reading and emulation all on the Arduino, which I bet you can (I’m sure you could do it all on a Propeller).

By the way, you should be able to modify the sketch so you can also hook the Parallax reader up to it for reading (which would then effectively make it a cloner). There were a couple of reasons I didn’t do this. First, I wanted to keep the project really simple so others could build on it and add whatever they wanted. Second, the Parallax reader reads EM4100 tags. It does read a lot of tags, but I was hoping to figure out a more generic reader, because you should be able to clone more tags using it.

By the way, when I picked up my reader a couple of weeks ago it was on sale at Radio Shack, the marked price was $49.99 but when they rung it up it was only $29.99. It looks like it’s been removed from their website so I think they’re closing them out.