🚀 go-pugleaf

> 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.