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Beating the unique identifiers that printers can add to documents for security purposes is possible: you just need to add extra dots beyond those that security tools already add. The trick is knowing where to add them.
[...] researchers from the Technical University of Dresden [...] Timo Richter, Stephan Escher, Dagmar Schönfeld, and Thorsten Strufe reckon they've cracked the challenge of knowing how to anonymise printed documents, and presented their work to the Association of Computer Machinery's 6th ACM Workshop on Information Hiding and Multimedia Security in Innsbruck, Austria [the week of June 22].
In this paper, the TU Dresden researchers explain that they tested 1,286 documents printed on machines from 18 manufacturers, creating an extraction algorithm to identify well-known dot-patterns--and at the same time, discovering four previously undiscovered patterns coding at 48, 64, 69, and 98 bits.
Identifying new patterns is important, from a privacy point of view, since as the authors points out, an activist in a dictatorship could easily be unmasked by their printer (unless they happen to use a Brother, Samsung, or Tektronix printer, none of which seemed to carry tracking codes, the researchers said).
[...] The group has published [a] toolkit that automates the obfuscation workflow, here.
Previous: "Printer Dot Sanitisation" Software Seeks to Cleanse Yellow-Dot Watermarks
(Score: 3, Insightful) by martyb on Thursday June 28 2018, @09:24PM (12 children)
So, assuming for the sake of argument that we cannot block the introduction of watermarking dots -- be they yellow or B&W -- how effective would it be to print the same document on multiple printers?
What I mean is:
Alternatively:
One could even have a network of folk who print reams of blank pages and exchange these reams among themselves for re-re-reprinting!
All are off the top of my head, so I must be missing something?
Wit is intellect, dancing.
(Score: 3, Funny) by frojack on Thursday June 28 2018, @09:37PM (1 child)
I thought of the same thing.
But even in the your best case, they now have to track down three printers. If they all are owned by you, or a couple of your friends, it won't take long.
Print at the library, or coffee shop that keeps lousy records? Might work better.
Most librarians go out of their way to not keep records like that.
Still picking up your print while wearing surgical gloves and a Guy Fawkes mask is bound to attract attention.
No, you are mistaken. I've always had this sig.
(Score: 4, Insightful) by vux984 on Thursday June 28 2018, @10:43PM
"But even in the your best case, they now have to track down three printers. If they all are owned by you, or a couple of your friends, it won't take long"
No, in the best case, it would be useless.
Imagine, for example, that the printer printed a barcode on each page; if they printed a binary id as series of black and blank spaces.
( This is essentially what they are doing. )
So if you ran it through multiple printers, each printing different barcodes or binary strings over top of the previous, the resulting barcode would not scan at all, or the binary string would just have more and more of its 'bits' set to black. Figuring out which combinations of barcodes summed together are resulting in the the final result might be a very large range of possibilities. (ideally, with barcodes, after you ran it through enough printers, you'd have a solid black bar, or a solid black binary code (e.g. all 1s)... which would tell you very very little, since practically infinite combinations of printers would get you that "pattern" or result.
(Score: 4, Interesting) by NewNic on Thursday June 28 2018, @10:33PM
Your idea is probably only going to make it easier to identify you.
The patterns of marks won't be aligned, so there will now be 3 identifiable sets of marks, which will indicate 3 printers. Tracking down who has access to the set of 3 printers is likely to lead to a smaller set of people.
lib·er·tar·i·an·ism ˌlibərˈterēənizəm/ noun: Magical thinking that useful idiots mistake for serious political theory
(Score: 1, Informative) by Anonymous Coward on Thursday June 28 2018, @10:42PM (3 children)
Easiest option: buy printer second hand for cash and dispose of it after the printing.
(Score: 0) by Anonymous Coward on Friday June 29 2018, @04:38AM (2 children)
This is the best idea here. Not highly technical. Anyone can do it. It's not illegal. It's easy to find a second hand printer. It's not expensive.
Win!
(Score: 0) by Anonymous Coward on Friday June 29 2018, @05:33PM (1 child)
Except, as someone pointed out above, your printer driver is collecting serial numbers and chatting away merrily to Windows Update server.
Lose!
(Score: 0) by Anonymous Coward on Saturday July 07 2018, @05:02AM
Who says they use Windows? Or the proprietary drivers?
(Score: 3, Funny) by Snotnose on Friday June 29 2018, @12:17AM
Ahhh, CSB time. Around 1990, when copiers where the size of a washing machine/dryer set and came with service contracts, our printer got the name Bob Marley cuz it was always jammin. Tech came out and spent a full day tearing it down to bare metal, and the next day putting it all back together. He ran a ream of paper through it printing a test pattern, then went to a conference room to do his paperwork. I took that ream of test patterns out of the trash, put it into the paper bin, and ran a few copies. Took my copy superimposed over the test pattern to the tech, said "scuze me but" and showed him. He turned white. I held it together for maybe 2 seconds before busting up laughing.
When the dust settled America realized it was saved by a porn star.
(Score: 2) by maxwell demon on Friday June 29 2018, @04:24AM (3 children)
I've got a simpler idea: If your goal is not artistic, you might simply use a solid yellow background. That way there's no place where the yellow printer dots could be printed.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by deimtee on Friday June 29 2018, @06:49AM (2 children)
The logic is probably smart enough to XOR the dots. You will print a solid yellow with the same pattern of holes in it. And it doesn't just print once, it repeats all over the page. Even if you know what you're looking for, it's almost invisible to the naked eye. Once you know, it is easily viewed with a X10 magnifier.
The ones I have seen (Xerox digital publishing machines) it looks like a string of 4 x 4 grids of dots, only some of which print. I assume the grid makes it easy to identify, and the missing/present dots encode the info. (I think it was 4x4, it's been a while, might have been 5x5). Pretty sure it wasn't one character per grid though, the strings were way too short to encode a unique SN 1 to 1.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by maxwell demon on Friday June 29 2018, @07:23AM (1 child)
In that case, make the background yellow random noise.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by deimtee on Friday June 29 2018, @09:12AM
The thing is, it is a very regular pattern of precisely sized dots that repeats multiple times. While you might obscure a random point on a grid, extracting a repeating signal buried in background noise is pretty much a solved problem.
If you cough while drinking cheap red wine it really cleans out your sinuses.