A Faster Cryptographer's Conspiracy Santa
Xavier Bultel (LIFO), Jannik Dreier (PESTO), Jean-Guillaume Dumas, (CASC), Pascal Lafourcade (LIMOS)

TL;DR
This paper introduces a secure, distributed method for settling shared expenses in a group gift exchange, significantly reducing transactions without revealing individual gift costs, applicable both physically and digitally.
Contribution
It presents a novel greedy distributed protocol for Conspiracy Santa that minimizes transactions and preserves privacy without relying on a trusted third party.
Findings
Reduces number of transactions to 2n + 1
Ensures no participant learns individual gift prices
Provides a secure solution applicable physically and via cryptocurrency
Abstract
In Conspiracy Santa, a variant of Secret Santa, a group of people offer each other Christmas gifts, where each member of the group receives a gift from the other members of the group. To that end, the members of the group form conspiracies, to decide on appropriate gifts, and usually divide the cost of each gift among all participants of that conspiracy. This requires to settle the shared expenses per conspiracy, so Conspiracy Santa can actually be seen as an aggregation of several shared expenses problems. First, we show that the problem of finding a minimal number of transaction when settling shared expenses is NP-complete. Still, there exist good greedy approximations. Second, we present a greedy distributed secure solution to Conspiracy Santa. This solution allows a group of n people to share the expenses for the gifts in such a way that no participant learns the price of his gift,…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
