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back to article How an ancient printer can spill your most intimate secrets

Researchers have devised a novel way to recover confidential messages processed in doctors' offices and elsewhere by analyzing the sounds made when documents are reproduced on dot-matrix printers. This so-called side-channel attack works by recording the “acoustic emanations” of a confidential document being printed, and then …

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Well there's a stroke of luck

And I only just threw out my DM printer too. Fifteen years ago.

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Brilliant

If you're only 2 centimeters away then why not just read it ?

Top boffinry.

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why not just read it from 2cm??

Because you might be noticed, hanging over the counter at the doctors surgery??

They might also have been better off using a different design of microphone as they get further away.

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Re: why not just read it from 2cm??

"Because you might be noticed, hanging over the counter at the doctors surgery??"

Whereas dangling a 7cm long microphone 2cm away from the printer would be far less conspicuous.

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Pint

@Liam Johnson

"Because you might be noticed, hanging over the counter at the doctors surgery??"

So read it by replacing the microphone thats 2cm away with a camera, which could probably be further away.

(Beer because I'm off to the pub in a bit :))

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Boffin

Re: why not just read it from 2cm??

"Whereas dangling a 7cm long microphone 2cm away from the printer would be far less conspicuous."

Bah. Just "forget" a bag with the microphone and recorder near the printer. Depending on the circumstances, it might stay in place for some time before anyone wonders. With suitable camoflaging, the presence of the equipment could also survive the bag being opened by the doctor's assistant.

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Alert

Dot Matrix !

My doctor's surgery in the UK went to laser printer some time ago.

Given the epic handwriting issues with British doctors this was probably a good thing.

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Encryption?

Maybe Doctors have a pen capable of encrypting their writing?

it would explain the jumbled mess they write

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Not only but also..

So who sends old ribbons for secure destruction? some types of ribon show exactly what was typed, (the ribon moves on after each keystroke) all you need to do is unwind the ribbon and hey presto every message ever typed..

anyway today its Thermal Laser and Inkjet that rule the roost, Old News.

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Oh yeah...

Nothing beats a Dot matrix printer when you're required to make a CarbonCopy, or use special multi-page forms with strikethrough.

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Boffin

News for ribbons

Ribbons are typically changed when the ink is diminished. Until then the ribbon has gone under the print heads dozens of times and deciphering text from the ribbon would probably need serious laboratory work.

You could as well ask who sends their laser printer's drum for secure destruction as the last pages printed could be restored as well.

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@ AC "News for Ribbons"

As the GP said, there are SOME types of ribbon ...

I had an IBM "Quietwriter". Its ribbon had a thin polythene (?) substrate with a thin film of ink on it. It was drawn once through from a feed spool to a take-up spool, and advanced after each character typed. Once all through the cartridge had to be thrown away. You could draw out the ribbon afterwards and read every word as transparent characters in the black ink.

Try winding it back for a second run, and the printed characters would miss bits of black where they co-incided with what had been typed on the first run.

It was very wasteful. Even if you had just one character on a line it would still advance the ribbon by the length of a whole line.

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Not all.

Some printers and electric typewiters use a 'one time' ribbon, similar to the ribbons used in labelprinters and such today.

(thin plastic film with a black coating that is transferred to the paper with an electric discharge)

Of course, most of those printers could use 'fax paper' insted of normal paper just by removing the ribbon. but those prints tended to fade over time.

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Two types of ribbon setting for Quietwriter

There was the full quality setting that advanced a complete letter at a time, and there was the draft quality setting, that actually only moved a fraction of a character position. This meant that you may get gaps in the later letters, where there was an overlap, but your ribbons lasted many times longer. This would make it much more difficult (though not impossible) to read from the ribbon.

I think that they were different ribbons, but it may have been a lever setting in the printer. I don't think it was a software setting.

These were actually thermal transfer printers rather than impact printers. This is how they managed to be so quite. Normal whirring from moving the print head and paper, but printing was silent.

Mine only advanced the ribbon for each letter printed (the ribbon was mounted on the print head), not on a per-line basis although mine was a Quietwriter III or IV and could have been different from Nuke's, so was not quite as wasteful as he suggested.

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Anonymous Coward

Carbon Ribbon

This was known as a "carbon ribbon" and such typewriters would be found on the desks of the secretaries of high-ups. The quality of the output was more akin to sharp print, or to the yet-to-be-invented laser printer. More advanced typewriters could do proportional spacing and even justification. Remember the IBM Golf Ball machine? That could even handle mixed faces.

The IBM electric typewriters of the day had a keyboard that was so sensitive that even breathing too hard produced a string of gibberish on the paper. Those who tamed it could type very fast on it.

Oh... I guess this was about Dot-Matrix printers, not typewriters!

Distinctive sounds, yes... I used to dance to them, in the office, while waiting for print to finish. You can't do that with a laser!

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Happy

Very good

Now I have to admit, that's pretty cool as 'ID theft' tricks go!

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Black Helicopters

If there's no audio sheilding...

...Then what's to stop the whole doctor-patient conversation being eavesdropped?

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Boffin

First side channel attack

I recall reading an article indicating remote reading of moving head hard drives going back to 1967.

Note the drives in question were the size of a twin tub washing machine.

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Easy to block...

This requires the words and letters to be written in sequence...

It shouldn't be too difficult to make the printer write a few characters, skip a few, write a few more, backtrack and fill in (part of?) the hole and so on.

Or, you could have it write the upper half of a line, then the bottom half on the return pass. Or maybe do an 'even/odd' dot pass?

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Megaphone

add noise generator to printer

rather than an acoustic hood (expensive, big, traps heat, makes access awkward), just add a small speaker to the printer that generates acoustically similar random noise while printing - it will be no louder than the print noise itself, and will mask the acoustic signature of the print head.

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Interesting

Interesting and Im glad some chap has had a brainwave, sat down and worked it out - alas while it is a nice bit of thinking I cannot see any pratical use for it. I myself use dot matrix printers at work to print out hire contracts on carbon copy paper - it certainly wouldnt be the end of the world if someone found out what was being printed...

Still, its nice to know it can be done!

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Anonymous Coward

And typewriters

According to Viktor Suvorov (if I recall correctly) in the specially suspended secure room inside a Soviet embassy, with noise generators between it and the surrounding walls, reports had to be written with a pencil as the sound of a typewriter, should it despite all the precautions be recorded by the enemy, could perhaps be analysed to discover what was being typed.

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Joke

title

"should it despite all the precautions be recorded by the enemy, could perhaps be analysed to discover what was being typed."

I've seen a certain Chicago living, wolf owning Canadian do this...

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Welcome

Don't mention the....

I, for one, welcome our carbon paper wielding, dot punching overlords.

Heil Merkel

Oh, sorry they tried something like that 60 years ago, after having tried it about 30 years before, and it didn´t really work.

(Why is there no "bad taste" icon?)

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Coat

Back when...

.. dot matrix printers were common I was doing computer maintenance. I could usually tell the type of printer they were using from the noise, even across the phone. The Epson MX-80 in particular made a hell of a din.

Ok the sun's out but I'll get it anyway.....

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Ho ho "Vorsprung Durch Technik" ?

So, technology has advanced beyond the physical carbon paper copy stage to the point where you can just tell your printer to print 2 copies (or even more if you want) and yet the Germanics are still using carbon paper and impact printing.

It's not like you couldn't simply print something different onto carbon paper, so it's not like it's a guarantee of anything.

More like "Rucksprung Durch Schreiberei".

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Anonymous Coward

Or, perhaps, using the "Technik" appropriate to the problem

"So, technology has advanced beyond the physical carbon paper copy stage to the point where you can just tell your printer to print 2 copies (or even more if you want) and yet the Germanics are still using carbon paper and impact printing."

Multi-part stationary is used for a reason - it makes things a little harder to forge, for a start...

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Anonymous Coward

could you not simply

be sure to run two or more dot matrix printers at the same time?

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Sure, today it's inkjey and laser

But one has to start somewhere, and it seems rather logical to use the most obvious system to weed out the errors first.

After all, what input is being used may have little influence once the patterns have been defined.

Thus, the next step of this boffinry is to ensure that recognition gets boosted to at least 95% in all cases.

After that, all that is needed is to define the patterns of an inkjet printer and presto ! Industrial espionage via the secretary's personal paper waster.

It's a work in progress, don't knock it.

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Joke

"The attack so far works only on English text"

But only if the printer types VE-RY SLOW-LY AND VE-RY LOUD-LY.

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Very slow and very loud

That would be the old Apple Imagewriter then.

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Boffin

Unfortunately

An Apple Imagewriter is actually just a rebranded C-Itoh.

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I suppose after they'd finished the research...

... they had to return the dot matrix printers to the Boston Computer Museum.

Pity they didn't think of doing this research in the 1970s, when it might have been relevant.

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Pint

Rather than bash the printing tech

I would like to congratulate what sounds like an amazing piece of coding!

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Joke

An amazing piece of coding?

They probably just found a Python module to do it.

>>>import listen_to_printer

>>>params = {"Epson":"MX-80"}

>>>print listen_to_printer.whats_it_saying(params)

It looks like the printer is printing a suicide note. Would you like me to help?

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FAIL

@parax

"anyway today its Thermal Laser and Inkjet that rule the roost, Old News."

Err, not when you want 24/7 unsupervised logging on contiuous paper they don't. And when you want a printer than can go 2 weeks doing said logging without bitching about a new toner/ink cartridge being required and refusing to work until its replaced. DMs will happily carry on printing no matter what the state of the ribbon.

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Oh really?

"DMs will happily carry on printing no matter what the state of the ribbon." -- maybe 9-pin ones. But 24-pin dot matrix printers are more sensitive, and a seriously-worn ribbon can bend a pin. Been through two print heads that way .....

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Doh

And just to prove the pointlessness of the research.. you give a '24/7 unsupervised' printer as an example of one that could be 'spied' upon! Doh! hardly difficult spying on that..

Of course there are specialist devices for specialist jobs. but today surely DM is less than 2% of printers.. hence does not rule in the world of printers.

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Who needs sound?

You don't need sound to monitor a dot matrix printer remotely - plenty of electromagnetic radiation from the print head drivers and it probably goes through windows and walls better as well. Even inkjet and laser printers, especially those in plastic cases, will probably radiate well enough to reveal their output to a suitably-equipped remote listener.

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Ignobel Prize Winner!

Great achievement guys. Usefulness in the real world - zero.

For your next trick, how's about traffic light sensors to detect a horse and cart waiting? Or a lightweight flashing red light as an improvement to the flag carried by the chap walking in front of your Model T Ford? Maybe even a gadget to let you know that your rapier is properly seated in its scabbard?

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FAIL

Retard

Guess this one didn't bother reading the "60% of doctors still use" part of the article.

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no history

Government Agencies, Doctors, Automotive Repair, Police Departments, ad infinitum are still using Dot Matrix printers. These printers are preferred due to low maintenance, low user intervention, and ability to print NCR forms. Sure, you can have your laser/inkjet print multiple copies, but there still runs the risk of it printing one form differently than the others (think contract law and legal proceedings).

As for a stoplight that can detect Horse & Buggy, such a sensor would be useful for motorcycles, cars made with non-ferrous materials, and even the, you know, Horse and Carts that are still seen in some parts of the country.

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"the rate dropped to about four per cent when the distance reached two meters."

Interesting proof of concept, but probably not so useful for espionage. Given the age of dot-matrix hardware, it might be simpler to look a little dongle between the printer and the parallel port? Hell, these days you could probably put a tiny microcontroller and an 8Gb flash chip in the parallel plug, record everything between "servicings".

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Boffin

Two words:

Laser mic. There are mics that work based on the vibration of the target - not the sound. They are used in surveillance, where You can point one to a closed window and "hear" what's going on inside.

Why not point one of these at the printer itself? Works from dozens (hundreds?) of meters.

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Bitch all you want about "old tech"...

But you can still buy Epson LX-300s new. OK, a £30 inkjet printer would knock the socks off it for quality and speed but an LX-300 will noisily bang away until the end of time itself. Perfect for logging jobs.

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Paris Hilton

Paris

San ld LX-300 would bang away noisily for years" - hope you nicknamed the printer Paris then (cos some had to. It's the law)

What will the massivly paranoid comd up with next. Work out how to steal some one's credcit card details by analysing someone's shit and work out which restaurant they ate at! Do these people ever leave their faraqday sheilded panic rooms

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Stop

Dot matrix printers aren't dead yet...

Whilst most of the world has moved on, I know a fair few UK Government departments are still relying on dot matrix printers to produce cheques...

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Happy

And they still use IE6 too...

...wait a minute.....

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Carbon copies

Why do we still rely on carbon copy paper? Surely this dates back to a time of no printers, or printers which were too slow to print everything out twice. Is there some antiquated law which dictates that carbon copy paper must still be used for certain things? If so, it's about time it was rescinded.

I suppose there is the case where you might require two copies of one signature. But then there has been plenty of times when I've had to sign certain paperwork multiple times.

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Pedantic, I know

but legally, there is a difference between two copies printed at the same time using multi-part stationery, and two copies printed one-after-another. There is no guarantee that the two serially printed sheets are identical, because they could just be one print after another, with the second one slightly different. How would you know unless you minutely compared them?

And yes, I know that the lower copies in a multi-part *could* have been pre-printed, but that is why they come bound together with tear-off sprockets, so that you can tell whether the lower copy has been tampered with.

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