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Created September 21, 2023 11:21
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Summary of Single Secret Leader Election paper
The passage introduces the concept of Single Secret Leader Election (SSLE), where a group aims to randomly select one leader without revealing their identity. It presents three constructions of SSLE schemes with varying security and performance properties. The first construction utilizes indistinguishability obfuscation, the second relies on low-depth threshold fully homomorphic encryption (TFHE), and the third is based on the Decision Diffie-Hellman (DDH) assumption and random shuffles.
The passage discusses the practical requirements and restrictions for SSLE schemes, the syntax and security properties of an SSLE scheme, and the algorithms and protocols involved in the leader election process. It also mentions the importance of security, fairness, and unpredictability in SSLE schemes.
One of the constructions presented is a TFHE-based SSLE scheme that uses a weak pseudorandom function (PRF), a threshold FHE scheme, and a random oracle. It explains the expansion of random bits into a vector, the leader selection process, and potential attacks such as duplication and modification attacks. The passage also discusses accommodating unequal election probabilities and PRF instantiation and optimization. It mentions the reduction of on-chain costs in blockchain use cases and proposes a simpler scheme with lower costs but weaker security properties.
In another section, the passage discusses unpredictability and fairness in the context of a Threshold Signature Scheme for Large Ensembles (TSSLE). It introduces threshold FHE to ensure unpredictability and presents a series of hybrids to prove this property. It also explains how fairness is achieved by generating the PRF key inside the threshold FHE and provides hybrids to prove fairness.
The passage further delves into the proof of two theorems related to the security of the system. It proves the uniqueness, fairness, and unpredictability of the system, with unpredictability demonstrated through a series of hybrids. The second theorem shows that if there is a distinction between two systems with a non-negligible advantage, it breaks the weak PRF security.
Lastly, the passage discusses Lemma 32, which states the probability that an adversary wins the unpredictability game is bounded by 1/N^(c) for some constant c. It also mentions modifying the security analysis to apply to a scheme where users' buckets are assigned randomly at registration time and shows that the scheme is (N-c)-unpredictable with at most negligible probability.
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