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It it legal to publish a list of cryptographic hashes of words and two- and three-word phrases from an article, in random order? "Lorem ipsum dolor sit amet" would become:

  • Lorem
  • Ipsum
  • Dolor
  • Sit
  • Amet
  • Lorem ipsum
  • Ipsum dolor
  • Dolor sit
  • Sit amet
  • Lorem ipsum dolor
  • Ipsum dolor sit
  • Dolor sit amet

The words and phrases would then be hashed with an algorithm such as MD5, and the hash list would be published in a random order. They will be mixed with such lists from thousands of other articles with no correlation between hashes and articles, so it will be virtually impossible to recover an article's text, even after recovering the words and phrases with a dictionary or brute-force attack.

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  • The fact that you're using MD5 already destroys the original data. So I'd say that even if you MD5 an entire protected work without any word shuffling, distributing just the MD5 is "not" a form of copyright infringement. Two related posts on this: law.stackexchange.com/questions/67593/… and law.stackexchange.com/questions/66668/…
    – Brandin
    Nov 24 at 9:53
  • However, if you MD5 each word or each short phrase, it's technically feasible to build a dictionary out of those hashes, so then you're possibly approaching copyright infringement territory. If I hash each word or phrase of an e-book, and then shuffle it with some well known algorithm, and then give you the result, then it's probably not too hard for someone to show how to reverse that well-known shuffling algorithm, and then to show how to reverse the hashes of all the words with a hash dictionary, to arrive back at the original e-book, thus proving copyright infringement.
    – Brandin
    Nov 24 at 9:58
  • What if the hashes are shuffled with those from thousands of other articles?
    – kj7rrv
    Nov 25 at 15:51
  • It's becoming more of a cryptographic and technical question, but I think it depends on the total length and the likely number of such phrases. Extensive dictionaries of the English language contain anywhere from 500k-1 million words/phrases, for example. Nowadays it is a trivial computational task to calculate hashes for 100 million words or phrases, and to store the result on your disk. Afterwards you would be able to use that result instantly to reverse your hashes back into words. Hence the purpose that you wanted to achieve from hashing (secrecy, anonymity) is lost.
    – Brandin
    Nov 28 at 7:08

1 Answer 1

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It is legal to publish clear-text words and short phrases from an article, because word and short phrases are not protected by copyright. It is therefore legal to publish a transformation of such words and phrases.

You can consider a given novel to be a sequence of words and short phrases. It is not legal to sequentially publish the words and phrases of a protected novel, for example as a web page with a million sequentially numbered chapters each containing a couple words of original text. It would be legal to alphabetically list all of the words employed in a novel, along with a token count.

In order to prove copyright infringement, the plaintiff in the lawsuit would have to prove that the allegedly-infringing work as a certain degree of similarity to the protected work. Suppose that the fifth word of the original and supposed copy is "the" – that is not sufficient similarity to prove copying. The question of degree of similarity is a very fact-intensive inquiry.

If a novel is in fact copied and run through the blender to produce unrecognizable word slurry, the plaintiff has the burden of proving the necessary degree of similarity between the original and the copy. This involves exposing the reconstruction procedure. Given any sufficiently large database of words (the word-count list mentioned above), one can also select words from the database so that the selection procedure maximally matches the original text (then you devise a mapping post hoc that "reconstructs" the original text from the slurry). The defense can counter this argument by positing a different algorithm that converts the slurry into Mother Goose rhymes. Whether not the plaintiff's argument that there was copying depends crucially on the uniqueness of the reconstruction.

So, the summary. First, words and phrases are not protected by copyright law. Second, entire works, which contain words and phrases, cannot be copied at all regardless of any transformations you apply. The law is stated in terms of copying, and not in terms of "creating a text that has a particular relation to a protected word". However, the law also has to deal with the known facts, and cannot require time-travel as a means of proving that there was copying. Therefore, the law takes "similarity" as a substitute for direct knowledge of an action in the past. It is therefore possible that a person can get away with actual copying, if the plaintiff cannot prove that the basis of the secondary text must have been the plaintiff's protected text.

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    If we consider just the clear text list of phrases, I think we'd have to run this through a fair use factor analysis to get a better idea of whether this is copyright infringement. A major consideration is the purpose of the use (which is not specified in this question). For example, if the purpose is to allow someone else (who knows how the list was shuffled) to reshuffle the list of phrases back to the original, then I'd say that is definitely not fair use.
    – Brandin
    Nov 24 at 10:03
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    "the plaintiff has the burden of proving the necessary degree of similarity between the original and the copy" - what is your basis for saying this? Buden of proof was a concept more appropriate for criminal cases. For a case of suspected copyright infringement, I believe the concept used is the "prepondorence of the evidence," I.e. the burden is not as high as you imply. In this example, if one can show that there is a 51% chance or greater that the "word salad" can be reshuffled back into an original (infringing) work, then that may indeed count as copyright infringement.
    – Brandin
    Nov 24 at 11:29

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