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I want to work on a project where you could replace a magstripe with another item which can change the data stored on it via a PIC but still be read by a magstripe reader. This means that the PIC could 'write' another value to the different tracks on a magstripe to replicate different cards. So what method could be used to do this? Would a magstripe be used?

tyblu
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Seidleroni
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3 Answers3

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The basic hardware behind magstripes is really the same as a tape recorder. It is divided into several tracks, and has a strobe track to sync everything up. You can buy the reader hardware, and I am aware of variants that are designed for writing. Check digikey. Make sure the reader/writer hardware you buy can read/write the track you intend.

wackyvorlon
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  • I'm looking for more of the physics of it. For instance, if I wanted to manually create a record, how would I do it? Would I create a voltage across a section of the tape? How much voltage? – Seidleroni Nov 29 '09 at 22:28
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    A coil is positioned very near the tape, to write a 1, the coil is energized and it magnetizes that spot on the tape. Reading is conducted similarly, the magnetized place on the tape induces a small current in the read head. – wackyvorlon Nov 29 '09 at 23:02
  • Could the magstripe be "simulated" by having metal strips with a small amount of voltage applied to them for the duration that they're read? Each strip would represent a "bit" for instance. – Seidleroni Nov 29 '09 at 23:30
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    @wackyvorlon: where are you getting your information? I'm pretty sure (but cannot find references online) that bits are encoded on magnetic strips using Manchester encoding, and NOT static levels, so that it is possible to use clock recovery techniques. I am also pretty sure that there are not several tracks and a strobe, but rather a single track. In any case it's useless to hypothesize unless someone can find a reputable source of information. – Jason S Nov 29 '09 at 23:31
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    hmm... found this: it appears you may be correct. http://www.epanorama.net/documents/smartcard/magcard.html – Jason S Nov 29 '09 at 23:33
  • It's pretty old-school technology. – wackyvorlon Nov 30 '09 at 15:29
  • Yes, but is there a way to replicate a magstripe using a PCB (and either coils in PCB wire to represent 1's or 0's when they are on or off?) – Seidleroni Dec 01 '09 at 00:39
  • I'm not certain there is. It's hard to figure the behavior of a coil on the PCB, and whether it would produce enough magnetic flux. On the normal device, the coil is wrapped around a laminated iron core that has a split where it contacts the magnetic strip. This creates much more flux than just the wire itself, and allows the flux to be better focused. I wouldn't hold out high hopes for a PCB with circular tracings producing enough flux. – wackyvorlon Dec 05 '09 at 20:16
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I remember watching a presentation by Acidus on his Stripe Snoop project... but I can't remember which con it was at. He had various types of readers, but he had one constructed out of an old cassette tape head. The head was manually moved to read the multiple tracks on the card. I know this is not quite the answer you are looking for, but it may help point you in the right direction! Here are some links to DIY mag card reading, software and hardware:

http://stripesnoop.sourceforge.net/hardware/hardware.html

morgellon
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  • this may help too, this is a setup using an arduino and a mag reader. part lists and schematics may help with your PIC project! http://hackmiami.org/2008/12/21/magnetic-stripe-card-reader/ – morgellon Dec 01 '09 at 07:32
  • these links may help as well... http://www.instructables.com/id/Magnetic_stripe_card_spoofer/ http://www.instructables.com/id/SMBGT71FJBYZ4QP/ – morgellon Dec 01 '09 at 07:35
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Sounds like you want to build a device like John Connor's ATM card/Atari Portfolio hack from the start of Terminator 2. Try googling mag stripe card spoofer.

Robert Atkins
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