Blockchains and Publicly-Verifiable Lotteries
summary
Describes concrete constructions and tradeoffs: classic commit–reveal needs penalties or an honest majority to prevent last-player aborts, threshold-signature MPCs tolerate minority failure but require many participants, and the modern square-and-prove VDF (Pietrzak/Wesolowski 2018) gives one-party honesty sufficiency but forces a long sequential delay and costly hardware. Gives real examples (50,000 diversity visas vs 3–5 million applicants; 366 draft capsules bias; NIST beacon 512 bits every 60 seconds) and notes Ethereum foundations pledge millions to fund VDF hardware.
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chapters (30)
- 0:00Intro
- 0:59The randomness beacon
- 4:35Negative lotteries
- 6:01Timeline for a verifiable lottery
- 8:34Randomness and zero-knowledge proofs
- 9:10Beacon-based zero-knowledge proofs
- 11:50Communication-efficient consensus protocols
- 13:21Historical example: sortition
- 17:11Consensus trilemma Communication efficient
- 17:59Nakamoto consensus uses random selection
- 20:04Natural beacons typically aren't unanimous
- 21:53Trusted third-party beacons
- 23:53Physical randomness generation
- 25:29Physical randomness can fail quietly
- 27:58Historical inspiration: The numbers game
- 29:34Financial market data
- 30:47Cryptographic randomness protocols
- 31:11Commit-reveal protocols
- 33:25The last-revealer problem
- 36:16Publicly-verifiable secret sharing (PVSS)
- 38:42Related approaches
- 44:40Comparison of approaches
- 46:56Blockchain-based beacons
- 47:25VDFs in one slide
- 48:57Observe: removing any of V,D,F is easy • Not verifiable: chained one-way function
- 51:51Exponent proofs in groups of unknown order
- 53:33VDF engineering challenges
- 53:49Candidate groups of unknown order
- 55:53Incentive questions: who computes the VDF?
- 56:57Non-traditional adversaries
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