Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!zaphod.mps.ohio-state.edu!mips!apple!portal!cup.portal.com!mmm From: mmm@cup.portal.com (Mark Robert Thorson) Newsgroups: sci.electronics Subject: Re: credit-card encoding (was Re: Wiegand wires?) Message-ID: <34388@cup.portal.com> Date: 29 Sep 90 20:21:25 GMT References: <5770030@hpscdc.scd.hp.com> <10960034@hpldola.HP.COM> <1990Sep25.153854.2812@zoo.toronto.edu> Organization: The Portal System (TM) Lines: 30 > Magnetic encoding is also quite a lot more difficult to duplicate than > optical encoding would be (without going to UV or someother such thing) > for your average (read "non-electronics hacker") person. Not necessarily. I've seen some very low tech gadgets for duplicating cards. Imagine a plexiglas box with a few strips of plexiglas on top to form two parallel channels, each the width of a card. Under each channel, inside the box, are two tape heads. An amplifier is connected from one tape head to the other. A card is duplicated by running the blank and the master through the channels while the amplifier is on. No mechanism is needed for feeding the cards through -- you slide them through using the same hand, so that both cards travel the same speed at the same time, even if the speed varies a little. Making a high-density optical card would be much harder, if lasers or holograms were needed. Even darkroom work would be harder than building a card duplicator from scratch. An even simpler way to duplicate a magnetic card is to place two cards together, with the blank on top. (You make a card blank by wiping a magnet across it.) Then quickly wipe a hot iron across the top card. This briefly heats the magnetic stripe above its Curie point. When it cools down, it picks up the field of the card on the bottom. WRT non-hacker types doing this, I heard about the iron technique several years ago, when it was rumored that tickets for the Bay Area Rapid Transit (BART) system were being duplicated in this way by the average citizens of places like Oakland. Note that BART tickets are heavy paper, like a postcard; this technique probably wouldn't work with a plastic credit card because of the thickness.