theinsider

Magstripe reader article in the new 2600

29 posts in this topic

Just thought I'd give a heads up to everybody about what appears to be a very nice article on building your own magstripe reader in the spring issue of 2600 that just came out.

Basically, it's just a cassette player head wired directly to a headphone plug, so you can record the waveform of the magstripe on your computer and use software to do all the dirty DSP work of decoding it to binary data. Benefits are:

- You can make it *tiny*

- You can read nonstandard tracks, and changing tracks is just a matter of changing the spacing

of where your card swipes past

- You can hook it up to a recorder and record card swipes to be processed later on your computer

Apparently they've been using this to play with the MTA cards in New York lately.

Has anyone built this yet and given it a try? I pulled a head out of an old generic walkman yesterday and when I get back in this evening I'm going to scrounge up a plug for it.

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did acidus write this one?

no, but he knows the person who did. They are working together on some things from what I understand.

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I need one for that thing I saw on that hackaday about cellphones and magnetic cards and how you can encode it to wav then decode it back to the data. I can do the same with my neuros, it has a built in mic and a ADC. probably can make it work with an ipod too

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actually i have yet to see the article but i call plagerism on whomever wrote that article already, if its being build the way you said, thats already been written by a engineer who graduated from my uni, name unknown but i have a copy of his thesis about decoding metrocard using that hardware and matlab for the decoding of the wav files generated, anyone who wants it feel free to ask. its sad to say that a few months ( i think ) after writing it he commited suicide for unknown reasons ( to me ) and unless credited id have to call plagerism on it, but thats just me being a bitch about it, anyone want a copy of the pdf just ask i think i have it on my hdd somewhere.

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anyone want a copy of the pdf just ask i think i have it on my hdd somewhere.

I want a copy of it. I am sure Acidus would love to read it also, so I will pass it on to him too.

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I would like a copy as well. It'll give me a reason to learn Matlab other than class and maybe shed some light on my copier card (damn you Intercard/Emos). I picked up a USB 3 track insert reader and does pretty well for normal cards, not the copier card though.

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oh dude, I would love to read that as well!

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Uhm, no. The article was not plagiarized from the pdf. The pdf was written by this Russian dude who went to Brooklyn Polytechnic University and then, in either late 2001 or early 2002, went crazy, stabed his girlfriend and then killed himself after a large confrontation with the cops. Anyway, the pdf does not have full info on the Metrocards and we think that it refers to the old Blue Metrocards instead of the currently in use yellow metrocards. Also the pdf doesn't mention the actual format of the data stored on the card. I'd post the pdf up right now but the computer upon which it's on is in shambles at the moment and I have to leave for work now.

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Uhm, no. The article was not plagiarized from the pdf. The pdf was written by this Russian dude who went to Brooklyn Polytechnic University and then, in either late 2001 or early 2002, went crazy, stabed his girlfriend and then killed himself after a large confrontation with the cops. Anyway, the pdf does not have full info on the Metrocards and we think that it refers to the old Blue Metrocards instead of the currently in use yellow metrocards. Also the pdf doesn't mention the actual format of the data stored on the card. I'd post the pdf up right now but the computer upon which it's on is in shambles at the moment and I have to leave for work now.

you might be right i-ball, i have yet to read all of it, i got about 60 pages in until the ADD kicked in and i got distracted with something stupid, like school. but the summer is here! ill take a look at it. and i-ball, btw, who is working on the metrocard stuff, i know godsmoke and jax0m were doing some stuff and that emmanual did a spot on OTH recently, oh and that kid that follows emmanual around all the time, was asking me about some stuff that i knew. how do people know waht im working on?!?! it depressing really.

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Trip report:

Well I tried putting this thing together as stated in the 2600 article, wiring up the cassette head to a phono plug, and have yet to get it to work. I used a ruler to measure out where the tracks should be and also as a straight edge to slide the head against. After some tweaking I could get binary out of the dab program, but never anything consistent or anything that could be decoded by the dmsb program.

One of a few things is wrong here:

- The head I ripped out of this crappy generic walkmanesque thing may not be sensitive enough

- Too much interference/noise involved in recording on my laptop

Also, if you want to play with this, test it out on a card you don't care about. I think it may have somehow demagnetized a walmart gift card I was trying it out on, since it didn't scan anymore at walmart the next day, but it could be unrelated since those things go bad on me all the time.

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i think i have issues. the only thing i do on the net anymore is search of mag stripe projects. i keep coming to Luis Padilla Visdómine site and on one of his pages he mentions the stripe erase issue. He suggest putting a capacitor in series with the read head

http://www.gae.ucm.es/~padilla/extrawork/soundtrack.html

never realized how much was out. Just started reading Acidus and Virgil's Blackboard Transaction notes. my college uses the system. i became interested after seeing the inside of laundry room control box.

need to get new 2600 to see what they did with metrocard. i have a card that's not readable by my current reader.

hope this helps

lostbaka

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Um, anyone notice how, 2 people who originally created similar devices both ended their own lives?..... mabey listening to the sounds generated played one after another makes you go nuts... Back to reality, its a shame they are both dead, I think.

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Um, anyone notice how, 2 people who originally created similar devices both ended their own lives?..... mabey listening to the sounds generated played one after another makes you go nuts... Back to reality, its a shame they are both dead, I think.

Wait...what?

2 people? What 2 people?

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From lostbaka's link:

Some sound cards have a stereo socket for the mic input, providing around +5v DC current in the middle connector (jack's ring), although I've seen at least one card with the +5v output in the outer connector (jack's tip), see here for details. If you use a mono jack connector (tip and ring shorted together) then this DC current is applied to the magnetic head and it might be enough to erase magnetic stripes (it happened to me with one sound card, I erased accidentally a couple of magnetic stripes while trying to read them), so you might consider adding a capacitor (around 200 nF should be fine) in series with the head to avoid this DC current. Of course you can use a stereo jack and leave the ring (or the tip) open, but anyway it's a good practice to measure the voltage before connecting the magnetic head to be sure there will be no DC current when you connect the head.

I bet this is exactly what happened with mine. I am using a stereo plug so I'll just disconnect the ring. I'll post my results later.

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ok this maybe as stupid idea but if wanted to encode on a card with the device described in 2600 could you connect it to the speaker port and use a motor to push it thought at a constant speed and "play" the new data by reversiving the reader code. Sorry but im new to all this and just had the idea cant program good. so i have no clue if it would work but just an idea

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You wouldn't need a motor to push it through because there is a clock track. This track tells it when there should be a bit of data.

I'm not sure if that makes sense.

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actually i have yet to see the article but i call plagerism on whomever wrote that article already, if its being build the way you said, thats already been written by a engineer who graduated from my uni, name unknown but i have a copy of his thesis about decoding metrocard using that hardware and matlab for the decoding of the wav files generated, anyone who wants it feel free to ask. its sad to say that a few months ( i think ) after writing it he commited suicide for unknown reasons ( to me ) and unless credited id have to call plagerism on it, but thats just me being a bitch about it, anyone want a copy of the pdf just ask i think i have it on my hdd somewhere.

yeah, i would like one.... cause i know nothing about magstripes and would like to learn...in case...you..wanted...to know...

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ok i understand perfectily but what if you wanted to encode a card with your sound card you will need to push the card passed the magnetic head as a constant rate or the data wount be in the right order on a card right? see the attached picture for a visual becouse i suck at ascII art

post-2358-1123741555_thumb.jpg

Edited by nanobot
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that would be difficult to set up, that is if you can encode it that way. I know that it is quite a bit harder to encode your own cards.

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