Is there a protocol for conducting a Secret Santa without a central authority? Precisely, we want to sample uniformly a permutation that has no one-cycles and reveal to each member his or her successor without revealing any other part of the permutation. Alternatively, we can uniformly sample an $n$-cycle, where $n$ is the number of participants in the Secret Santa.

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    $\begingroup$ rodrigosetti.com/cryptography/cryptographic-secret-santa $\endgroup$ – Carlo Beenakker Dec 18 '17 at 20:39
  • $\begingroup$ This is precisely what I wanted! I have a followup question. Is there a protocol that doesn't rely on encryption? Preferably one that could be used in person without a computer, like the protocol for secure addition. $\endgroup$ – Vodka Dec 18 '17 at 20:46

Cryptographic Protocols with Everyday Objects (section 5)

Typical cryptographic Secret Santa protocols require a fully homomorphic encryption system. These protocols are thus suitable for those with some planning, some expertise and access to computational assistance, but not to a group of friends without access to computers. Here we present an alternative solution, which does not lower the security requirements, and does not require anything beyond card, envelopes and pens.

  • $\begingroup$ math.stackexchange.com/a/1054676/30836 gives an equivalent protocol which may be physically slicker. $\endgroup$ – Micah Dec 18 '17 at 21:51
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    $\begingroup$ @Micah: Personally, I find the envelope-based solution quite a bit more practical than anything that involves cutting up cards and stapling them together (not to mention trying to shuffle the stapled-up cards). But I guess that's a matter of taste. $\endgroup$ – Ilmari Karonen Dec 18 '17 at 22:10

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