Suppose I want to talk with a co-worker about a movie called "The Twist Movie". I know the movie contains an interesting twist, and bringing up the movie in a discussion about twists in movies might spoil the first time experience of someone who has not watched that movie, because now the viewer knows to expect the twist.

Is there an algorithm so that both parties can verify beforehand that both know the movie without sharing the information about the movie? (So neither side gets spoiled by mentioning the movie)

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    $\begingroup$ Hey I saw the movie. Good I didn't. Now don't spoil. What is the need here? $\endgroup$ – kelalaka Aug 22 '19 at 14:40
  • $\begingroup$ In your security game is the goal to avoid to spoil someone who didn't see the movie but pretend to have seen it? $\endgroup$ – Ievgeni Aug 22 '19 at 14:42
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    $\begingroup$ Hash commitments of the written plot. Perhaps with fuzzy hashing. Multiparty computation to compare written plots for similarity. Private set intersection for a set of plot points (with identifying numbers for ordering), perhaps paired with a Zero-knowledge proof against a hash commitment against your set to prove no repetitions (requires exact canonical encodings to ensure no disagreement based on terminology). $\endgroup$ – Natanael Aug 22 '19 at 19:21
  • $\begingroup$ How can we get you to write more answers, Natanael? Don't worry if they are partly incorrect, we'll comment, edit or - of course - downvote them to heck :P $\endgroup$ – Maarten Bodewes Aug 22 '19 at 21:52
  • $\begingroup$ @MaartenBodewes I'm writing from my phone, I'm to lazy to post as answers $\endgroup$ – Natanael Aug 22 '19 at 23:02

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