
Spraying Magnetic Stripe Cards with Iron Filings - charlieirish
http://www.tetherdcow.com/another-science-experiment/
======
Animats
Yeah, the ShooTag thing is totally bogus.

Viewing magnetic recordings with magnetic particles used to be a standard
maintenance tool. It was used to check tape drive head alignment. There was a
liquid with iron particles in suspension into which you could dip a strip of
tape. When the solvent evaporated, you could see the data tracks. A non-
destructive version was a hand-held viewer, with a window on top and a thin
plate on the bottom, filled with a fluid containing iron particles. You could
press this against a tape and view it.

These were sometimes used in data centers during the transition from 7 to 9
track tape drives, when an incoming tape had an unknown format.

~~~
rtanaka
The liquid (also comes in spray form) still exists. It's called a Magnetic
Developer:
[https://en.wikipedia.org/wiki/Magnetic_developer](https://en.wikipedia.org/wiki/Magnetic_developer)

~~~
seanp2k2
Wow, never heard of this. Gotta love the old-skool tech!

~~~
MichaelCrawford
The very first time I wrote an interrupt handler, it was in octal, entered by
a numeric keypad into an LSI-11 with DEC's ODT - "Octal Debugging Technique".

I wish I could say I was paid to do that but it was for UC Davis' Intro to
Computer Architecture Class.

I got a C because I cratered the final.

------
nkurz
A beautiful story about the inner workings of a patent-pending species-
specific insect repellent based on a small strip of magnetic strip. As one
might guess, it involves encoding the words "FLEA" and "TICK" on the strip. Or
maybe "AELF" and "KCIT" to properly actuate the quantum polarity? The story
was written in 2010 while the patent was still pending. But surely it's been
rejected by now. Nope. Also as one might guess, the patent was granted by the
USPTO with the the main claim intact:
[https://www.google.gg/patents/US8382001](https://www.google.gg/patents/US8382001)

Have you ever thought to yourself "Sure, this advertisement says 'patent-
pending', but that only means that someone was able to scrape together enough
money to file a patent. It's not like someone has vetted the technology and
actually granted them a patent." Well, now you see that you can safely shorten
that to "Sure, this advertisement says 'patented', but that only means that
someone was able to scrape together enough money to file a patent. It's not
like someone has vetted the technology."

This is probably not surprising to anyone who understands the role of patents.
They aren't designed to act as evidence that a technology is useful, or even
possible. Instead, they are designed to "promote the Progress of Science and
useful Arts", which seems to be interpreted as to "create a secondary market
for dubious patents". I was surprised though to see that they had been granted
a second patent, covering the ornamental design of the tag:
[http://www.google.com/patents/USD626704](http://www.google.com/patents/USD626704)

I was aware that design patents existed to cover essential innovations such as
the rounded corners of a "portable display device"
([http://www.google.com/patents/USD670286](http://www.google.com/patents/USD670286)),
but I hadn't realized how broadly they could be applied. Is there a threshold
that needs to be exceeded when determining how much the grant of a design
patent will "promote the Progress of Science and useful Arts"? Or can one
expect to receive design patents for any design variation you can dream up?

~~~
DanBC
The article is from 2010. Amazingly shootag is still on sale at Amazon. $35
for two! They have 150 reviews. 42% 5 star, 12% 4 stars and 31% 1 star.

The reviews seem to have many genuine people who _absolutely believe_ these
work - even though these things clearly can't work. Reading the reviews makes
me a bit angry and a bit sad.

~~~
steve19
Rational wiki points out that it is vaugly possible they do work, although not
by the mechanism claimed. if they were heavily coated with chemicals they
might work... while possibly poisoning the pet they are being used on.

~~~
0942v8653
> shoo!TAG is a revolutionary chemical-free way to protect your pets from
> fleas and ticks

I don't think so. But I _highly_ doubt the card is actually chemical-free, so
they're lying either way. Also, I think they would be more afraid of lawsuits
by people whose pets were poisoned than for false advertising.

~~~
madaxe_again
The card comprises a unique matter-free pocket universe. Or at least it had
better, or they're lying.

~~~
eru
As long as it's not atoms, but eg just neutrinos, it's not really chemistry.

------
DanBC
You used to be able to buy magnetic field viewers to inspect tape. Here's a
picture of one: [http://nickapedia.com/2011/02/21/back-to-the-geek-future-
coo...](http://nickapedia.com/2011/02/21/back-to-the-geek-future-cool-old-
stuff/)

Another fun thing you can do is put the iron filings in a jar with mineral
oil. Give it a good shake, then put a strong magnet on the side. You'll be
able to see the magnetic field in 3D.

------
3JPLW
Don't miss the comment where they decode the ShooTag magstripe to contain the
DEC-SIXBIT ASCII strings "FLEA" and "TICK":
[http://www.tetherdcow.com/another-science-
experiment/#commen...](http://www.tetherdcow.com/another-science-
experiment/#comment-297446)

Sure to repel them, that.

Also, note (2010).

~~~
rotten
I wonder if you made one that said "hot babe" it would be a chick magnet.

~~~
dkersten
Chick repellant.

------
Others
What I'm confused about here is why the ShooTag actually has any data on it at
all. Surely it would be cheaper to just make part of the plastic card black,
instead of actually going to the trouble of encoding something on it.

~~~
tikhonj
One thing to consider is that the creators might very well believe it works
themselves.

It's easy to fool yourself into believing something you _want_ to believe.
They might even have done some informal, poorly structured tests and gotten
the results they were expecting for other reasons, reinforcing their beliefs.
Hell, I've done this to myself (ie when debugging) so I can totally empathize.

~~~
freehunter
I would probably die of embarrassment if anyone ever saw the number of lines
in my code that say

x = x //this doesn't need to be here but it breaks if you remove it

~~~
moron4hire
Wouldn't it be better to figure out _why_ it breaks?

~~~
jrockway
The five whys should be applied to successes in addition to failures.
[https://en.wikipedia.org/wiki/5_Whys](https://en.wikipedia.org/wiki/5_Whys)

If you figure out some amazing workaround, ask yourself why it works. If you
don't know, don't trust the workaround.

~~~
freehunter
If you question it, you might find a way that works better. Then you have to
redo all of it, and that's more work, so just keep plugging away, blissfully
ignorant!

------
luck87
For the same reason, the ferromagnetic nature of the magstripe, it is possible
to read, store and playback the data information on the stripe. You need only
few $ for the reader or a simple Square reader. This is an alternative
solution to spoof Magnetic stripe cards on Android:
[http://cosmodro.me/blog/2011/mar/25/rhombus-square-
iskewedi/](http://cosmodro.me/blog/2011/mar/25/rhombus-square-iskewedi/)

~~~
flax
Hey, cool, it's nice to see my stuff get referenced by someone that isn't me!

Rhombus only _reads_ magnetic stripe data. It won't write it. But yes, you
could totally write to a low-coercivity stripe with the right hardware.

Before you run out and get a Square reader, they're all encrypted now and
don't return the raw data necessary for Rhombus to work. You can still get
unencrypted readers from China on alibaba pretty easily.

~~~
luck87
There are same crazy nerd which enjoy themself (I don't know why) to decrypt
credit card data coming off of a magnetic stripe scanner:
[https://www.parthenonsoftware.com/blog/how-to-decrypt-
magnet...](https://www.parthenonsoftware.com/blog/how-to-decrypt-magnetic-
stripe-scanner-data-with-dukpt/)

But I agree with you, an un-encrypted reader of magnetic stripe is very easy
to find or build. The security is like a door in the desert.

------
madez
Question:

    
    
        Will this interfer with their invisible fence collars?
    

Answer:

    
    
        I wouldn't know the answer to that for sure - but would not
        hesitate to use with an invisible fence. This is not an electric
        type mechanism but rather one of kinetic energy - thus based
        on the dogs movement...as they move they create body energy
        and the tag works to keep critters away...not related to any
        electrical devices etc. I believe on the Shoo Tag site you can
        reach out to them and there are FAQ's, I'm sure they can
        clarify 100%.
    

Source: [http://www.amazon.com/interfer-their-invisible-fence-
collars...](http://www.amazon.com/interfer-their-invisible-fence-
collars/forum/Fx29K5XDBM2ROGB/TxFT1NCVR7Y0JB/1/ref=cm_cd_ql_tlc_al?_encoding=UTF8&asin=B0021L8XBO)

Where, again, was the possibility to opt out of being human? I really
should’ve had been paying more attention.

------
stephengillie
It might be interesting to perform this same experiment with a Coin Card. It
would be cool to see the patterns shift as it remagnetizes its bars.

------
codezero
In one of my experimental physics courses we built a circuit to digitize the
data on magnetic cards. It really blew my mind when I realized how it was
designed to allow variable swipe speeds. If you think about it, it's very
cool.

------
omgitstom
Metal filings can wreck havoc on your lungs / eyes - please use safety
precautions if you are attempting this at home

------
PirateDave
When he pulled the ShooTag out I thought he was totally going to write the
card data to it. Nonetheless, interesting article.

------
atamyrat
You can use laser printer toners to get same effect! They are magnetic as well
and might be easier to get.

It's also easy to get better contrast - apply transparent tape to magnetic
strip, remove the tape and put it on top of white paper. You can clearly see
strips.

------
mgrennan
Nothing new here. I was doing this back in the 80 to check on the alignment of
8" floppies and backup tapes.

~~~
nkurz
I downvoted your comment, but then noticed that you have only made two
comments here, so this felt needlessly cruel. So I upvoted your first comment
as recompense. Your first one was a fine comment. This one is not.

I'd be glad to hear more about using this technique to check alignment of
floppies. In fact, the top rated comment on this page is about that. But
saying "Nothing new here" is unwarranted and crass. While this may be old hat
to you, it's interesting to many who might not have considered it.

Perhaps more importantly, only the first part of the article is about visually
checking the magnetic strip. The rest is about enhancing it using image
enhancement, decoding it by guessing likely parity codes, and then detailing
years of unsuccessful attempts to discourage people from buying this
fraudulent product.

Anyway, welcome to HN and please stick around to share your experience by make
more comments like your first one.

~~~
sebastianavina
he is a true veteran, he doesnt care if his comments are popular or not

------
aplc0r
There is also magnetic developer:
[https://en.wikipedia.org/wiki/Magnetic_developer](https://en.wikipedia.org/wiki/Magnetic_developer)

This is what is usually used today to diagnose issues with magnetic stripe
encoding/reading.

------
pbreit
Is there a learning here that something so simple and reliable can work so
well for 60+ years despite constant ridicule from in-the-know tech and
supposed "insecurity"?

~~~
freehunter
If it's stolen as often as it is, it doesn't really "work so well". It worked
well up until it started being used and stored on Internet-accessible
machines. As soon as that happened, it utterly failed to "work so well".

If you want to know about its "supposed" insecurity, maybe read any of the
hundreds of articles online about Target, Staples, Home Depot, PF Changs,
Neiman Marcus, Goodwill, Global Payments, UPS, Michaels, and dozens more. I'm
not sure what you're arguing, that magstripe is safe enough?

~~~
TeMPOraL
Magnetic stripe is about as secure as your door key. It's all great as long as
it sits in your pocket, but post a close-up photo of it accompanied by your
address to Twitter and see how long it takes until the things from your flat
start mysteriously appearing on Craigslist.

