Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with A. Steger, D. Steurer and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Tuesday, March 05, 2024, 12:15 pm

Duration: 30 minutes

Location: OAT S15/S16/S17

Speaker: Seth Pettie (University of Michigan)

Algorithms Should Have Bullshit Detectors! (or Polynomial Time Byzantine Agreement with Optimal Resilience)

One thing that distinguishes (theoretical) computer science from other disciplines is its full-throated support of a fundamentally adversarial view of the universe. Malicious adversaries, with unbounded computational advantages, attempt to foil our algorithms at every turn and destroy their quantitative guarantees. However, there is one strange exception to this world view and it is this: the algorithm must accept its input as sacrosanct, and may never simply reject its input as illegitimate. But what if some inputs really are illegitimate? Is building a "bullshit detector" for algorithms a good idea?

In this talk I will present a protocol for asynchronous Byzantine Agreement against the "strongest" adversary, which is omniscient, computationally unbounded, and can adaptively corrupt players as the protocol progresses. The protocol reduces Byzantine Agreement to a coin-flipping game in which the nominal goal is to collectively flip a fair coin, in the presence of malicious parties that attempt to fix its outcome. However, in the short term the malicious parties have an insurmountable advantage. The true goal of the game is to build a sound "bullshit detector" that identifies which parties are not playing according to protocol, and "blacklist" them.

https://arxiv.org/abs/2206.15335. J. ACM, 2024.


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