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Be careful what you copy: Invisibly inserting usernames into text

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Re: Be careful what you copy: Invisibly inserting usernames into text

#21

Post by ry_ry »

zbobet2012 wrote: post #9

I did this (non-publicly) many years ago for my eve online alliance. A substantial problem exists in that forging the identity of _someone else_ is fairly easy in a naive scheme if someone detects these characters. That means you can sow chaos by blaming innocent folks. In practice you'll want to "sign" the inserted data as well. Also because of the overhead here and the fact that you will want the signature to occur…

Later, we just told select people we had implemented some crazy undetectable watermarking, and the leaks stopped - effectively identifying the culprits in the process.

Re: Be careful what you copy: Invisibly inserting usernames into text

#22

Post by ChuckMcM »

IBM did something similar with unused high order bits in a firmware image that Memorex was accused of copying. This was the first time I've seen zero width characters used, presumably you could build a brainfuck compiler that would let you write code as zero width spaces :-) Then you could have an invisible script inside your document. Fun but not particularly useful.

EDIT: Or a whitespace interpreter (https://en.wikipedia.org/wiki/Whitespace_(programming_langua...)

Re: Be careful what you copy: Invisibly inserting usernames into text

#23

Post by zbobet2012 »

elaus wrote: post #17
zbobet2012 wrote: post #9

I did this (non-publicly) many years ago for my eve online alliance. A substantial problem exists in that forging the identity of _someone else_ is fairly easy in a naive scheme if someone detects these characters. That means you can sow chaos by blaming innocent folks. In practice you'll want to "sign" the inserted data as well. Also because of the overhead here and the fact that you will want the signature to occur…

> There are other, far more interesting ways, to watermark text than this that are both harder (to impossible) to detect that produce better results. This sounds interesting, could you elaborate?

The post above mentions some. One good way is synonym replacement. In this method the actual _text_ is altered every time to produce a unique arrangement of synonyms used through out the text. For example I can replace "two" with "2" or "fast" with "quick" to obtain a bit to embed things in. See here for examples:

http://failheap-challenge.com/showthread.php?16311-Taking-th...

Another is to alter the _frequency_ of certain letters occurring in the text to produce a unique watermark. For example the "number of i's" that occur in the text can be used to produce a unique text per user. This is a very hard attack to detect or do anything about because even _summaries_ of the associated text tend to carry letter and word frequencies forward.

These methods are also impervious to "screenshot" etc. And because the embedded value can simple be a 64bit key to lookup the users/session info with attacks that attempt to impersonate other are impossible.

Re: Be careful what you copy: Invisibly inserting usernames into text

#24

Post by [deleted] »

zbobet2012 wrote: post #23
elaus wrote: post #17

Earlier quoted context omitted.

> There are other, far more interesting ways, to watermark text than this that are both harder (to impossible) to detect that produce better results. This sounds interesting, could you elaborate?

The post above mentions some. One good way is synonym replacement. In this method the actual _text_ is altered every time to produce a unique arrangement of synonyms used through out the text. For example I can replace "two" with "2" or "fast" with "quick" to obtain a bit to embed things in. See here for examples: http://failheap-challenge.com/showthread.php?16311-Taking-th... Another is to alter the _frequency_ of c…

[deleted]

Re: Be careful what you copy: Invisibly inserting usernames into text

#25

Post by avree »

zbobet2012 wrote: post #9

I did this (non-publicly) many years ago for my eve online alliance. A substantial problem exists in that forging the identity of _someone else_ is fairly easy in a naive scheme if someone detects these characters. That means you can sow chaos by blaming innocent folks. In practice you'll want to "sign" the inserted data as well. Also because of the overhead here and the fact that you will want the signature to occur…

which alliance were you in? :)

Re: Be careful what you copy: Invisibly inserting usernames into text

#26

Post by Mashimo »

ry_ry wrote: post #21
zbobet2012 wrote: post #9

I did this (non-publicly) many years ago for my eve online alliance. A substantial problem exists in that forging the identity of _someone else_ is fairly easy in a naive scheme if someone detects these characters. That means you can sow chaos by blaming innocent folks. In practice you'll want to "sign" the inserted data as well. Also because of the overhead here and the fact that you will want the signature to occur…

Later, we just told select people we had implemented some crazy undetectable watermarking, and the leaks stopped - effectively identifying the culprits in the process.

You could say, you snuffed them out!

Re: Be careful what you copy: Invisibly inserting usernames into text

#28

Post by spicyj »

zbobet2012 wrote: post #23
elaus wrote: post #17

Earlier quoted context omitted.

> There are other, far more interesting ways, to watermark text than this that are both harder (to impossible) to detect that produce better results. This sounds interesting, could you elaborate?

The post above mentions some. One good way is synonym replacement. In this method the actual _text_ is altered every time to produce a unique arrangement of synonyms used through out the text. For example I can replace "two" with "2" or "fast" with "quick" to obtain a bit to embed things in. See here for examples: http://failheap-challenge.com/showthread.php?16311-Taking-th... Another is to alter the _frequency_ of c…

How do you synthetically alter the frequencies of letters?

Re: Be careful what you copy: Invisibly inserting usernames into text

#29

Post by ry_ry »

Mashimo wrote: post #26
ry_ry wrote: post #21

Earlier quoted context omitted.

Later, we just told select people we had implemented some crazy undetectable watermarking, and the leaks stopped - effectively identifying the culprits in the process.

You could say, you snuffed them out!

Kings of lowsec watermarking.
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