[HN Gopher] Embedding information in text documents using glyph ...
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Embedding information in text documents using glyph perturbation
(2018) [pdf]
Author : epilys
Score : 51 points
Date : 2022-04-21 13:26 UTC (9 hours ago)
(HTM) web link (dl.acm.org)
(TXT) w3m dump (dl.acm.org)
| photochemsyn wrote:
| Makes you wonder if the linked pdf itself incorporates this
| method and there's a secret message hidden in it.
| HidyBush wrote:
| A long time ago I thought about a similar method but applied to
| music. What if you injected in every sold or streamed version of
| a song some kind of slightly different version of an instrument?
| Maybe if the piece has a cowbell it could ring at imperceptibly
| different times and frequencies, thus generating a unique
| fingerprint.
| LarsAlereon wrote:
| They already do audio watermarking like this and it can be
| annoyingly audible, it sounds kind of like a warbling or volume
| variation noticeable on sustained notes. At first I thought it
| was Youtube compression and then I started noticing the same
| thing in other streaming services. I switched to listening
| through subscription services offering HD audio which is
| watermarked differently in a way I can't hear.
| woliveirajr wrote:
| Take the letters "a" from the page 3, top right, and combine all
| them in your Gimp [0]. It's amazing how it's hard to distinguish
| those letters without the help of some tool.
|
| I always thought about it when some people question, for example,
| the secrecy of the vote. When you're given the ballot, there's no
| way to know if all them are the same or if each one has some
| codified information without extensive audit. Even scanning all
| the ballots will introduce small imperfections that will make it
| hard to audit everything.
|
| [0] Letters 0 and 1, letters 2 and 3: https://imgur.com/a/9v5W7Ib
| renox wrote:
| In France when I voted with papers, the ballots were in stacks
| and _you_ picked the ballots then went to an isoloir(doesn 't
| know the English word sorry) to fill your envelope: they
| weren't given to you. So this wouldn't work.
| woliveirajr wrote:
| I though in a scenario where the ballots are in a stockpile
| and you pick up the top one. If they are secretly numbered,
| it doesn't matter which one you did pick up: it's just
| necessary to register who was the first to vote and so on.
|
| This can de done by anyone. Example: the person that is
| checking your ID before you pick the ballot.
| renox wrote:
| It wouldn't work: in theory you were indeed supposed to
| take one ballot for each candidate, but in practice some
| made a show to not pick some candidate, other took several
| papers..
|
| I remember opening envelopes where several ballots for the
| same candidate were put together in the same envelope, a
| very bad idea as this meant that this envelope wasn't
| considered a valid vote..
| lifthrasiir wrote:
| Voting booth, I believe. That's indeed really a good idea
| that one can readily implement without a huge cost. Was there
| any incident that prompted such a voting protocol?
| renox wrote:
| If there was one, I'm not aware, sorry. It may just be an
| easy way to handle the 'distribution' of ballots. Obviously
| they _gave you_ the envelope.
|
| Unfortunately now they use electronic voting, a clear
| regression for transparency :-(
| teddyh wrote:
| Are you given a ballot which could be customized for you, or do
| you simply pick one from a pile?
| mdb31 wrote:
| "Provided a text document with specific fonts" is doing a lot of
| heavy lifting here.
|
| Pretty much by definition, text documents don't supply fonts. So,
| reading text documents is still fine, unless your OS "helpfully"
| opens text documents using _rich_ text viewers, in which case:
| please talk to your OS vendor.
|
| For _rich_ text documents, say PDF, the risk of personalized-and-
| or-remote embedded fonts is not exactly new. Maybe this variant
| is, but the general idea definitely isn 't.
|
| So, this, to me, is at best a possibly-novel "how to do DRM with
| PDF" technique. Which is interesting, but not exactly earth-
| shattering.
|
| Or am I missing something here?
| orhmeh09 wrote:
| What's your definition? Here's theirs:
|
| > Our FontCode system embeds in a text document any type of in-
| formation as a bit string. For example, an arbitrary text
| message can be coded into a bit string using the standard ASCII
| code or Unicode. We refer to such a bit string as a plain
| message. In a text document, the basic elements of embedding a
| plain message are the letters appearing in a particular font
|
| I think you're talking about the plain message. There's nothing
| wrong with their definition of text document.
| avisser wrote:
| > There's nothing wrong with their definition of text
| document.
|
| I think we can agree that it could be more specific. Me and
| OP read "text document" and hear "plain-text file".
|
| The article talks about using Word. If someone sent me a Word
| document and called it a "text document" I'd look at them
| cross.
| dwringer wrote:
| Well, if you print it out then it's all kind of embedded on a
| piece of paper.
| epilys wrote:
| > "how to do DRM with PDF" technique
|
| Not DRM, but fingerprinting? Sure. This gives me the idea to
| write a PDF sanitizer that resets glyph rotation and kerning to
| prevent this.
| Hizonner wrote:
| Well, goodness. They appear to have reinvented the Baconian
| cipher. Only what, 417 years late?
| mordechai9000 wrote:
| I remember there was a shareware x86 assembler called A86 back in
| the 90s. It was easier to use than Microsoft's. In the
| documentation, it said it would encode a fingerprint in the
| output opcodes so they could go after anyone using it for
| commercial purposes without a license.
|
| This would be possible (according to them) because there are
| instructions that could be encoded in multiple ways without
| affecting the operation of the code.
|
| I wonder now if they actually bothered, or if it was just there
| in the docs to make cheapskates think twice.
| no-s wrote:
| disturbing, if true...
| sly010 wrote:
| Meh, this wont even survive a xerox :) [0]
|
| [0] http://www.dkriesel.com/en/blog/2013/0802_xerox-
| workcentres_...
|
| TLDR: xeroxes try to compress documents by replacing _similar_
| glyphs with the _same_ glyph.
| btrettel wrote:
| Reminds me of this similar technique using zero-width characters:
|
| https://medium.com/@umpox/be-careful-what-you-copy-invisibly...
|
| https://news.ycombinator.com/item?id=16749422
| adultSwim wrote:
| Bad time to be a whistler blower
| Findecanor wrote:
| Haven't printers for a long time embedded uniquely identifying
| codes into printed pages?
|
| I thought it was standard practice so that FBI would be able to
| match ransom notes and threatening letters with the printers
| they originated from.
| teddyh wrote:
| Color printers, yes. https://www.eff.org/issues/printers
| woliveirajr wrote:
| Video and demonstration:
| https://www.youtube.com/watch?v=dejrBf9jW24
|
| Talk: https://youtu.be/2DAlv8aw34Y
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