Revision History for: Leader Election
- 2025-05-15 at 14:56 by Mina Doosti
Functionality Description
Leader Election is a multi-party cryptographic functionality that allows a group of parties to securely and fairly elect a single leader from among themselves[1,2]. It’s a core building block in distributed systems and blockchain protocols where coordination is required but trust is minimal. The functionality ensures that the elected leader is selected according to well-defined fairness criteria, and crucially, that adversaries cannot unduly influence or predict the outcome.
Protocols
No protocols implement this functionality yet.
Classical Analogues
Leader Election is an originally classical functionality, and so there exist many classical protocol that implements it.
In classical distributed systems, leader election is often used in consensus protocols such as Paxos or Raft, where the leader coordinates agreement on the system state. These protocols assume crash or benign faults, and typically don’t offer cryptographic privacy or unpredictability guarantees. In modern decentralized and adversarial environments (e.g., blockchains), these assumptions break down. Leader election must defend against adversaries who might try to influence the election or implement other attacks, such as denial-of-service attacksClassical cryptographic approaches generally include:
- Public randomness-based selection and coin-flipping-based protocols
- Leader rotation or round-robin mechanisms
- Verifiable Random Functions (VRFs) in systems like Algorand
- Proof-of-stake leader selection in Cardano and Ouroboros.
Real-world Use Cases
Cryptocurrencies and Blockchains:
- Electing block proposers or validators in protocols like Ouroboros, Algorand, and Ethereum 2.0
- Preventing adversarial targeting of leaders (SSLE[3])
Anonymous Coordination:
- Electing a party to initiate a sensitive task without revealing their identity in advance (e.g., whistleblower or keyholder activation)
Decentralized Randomness and Committees:
- Choosing a subset of participants for committee-based protocols
Resilient Multi-Party Computation
- Selecting a party to initiate or finalise computations while maintaining privacy
Properties
Leader election schemes may have different properties, but the main important ones include:
Uniqueness: The protocol always results in the election of a unique leader (possibly secret).
Fairness: All honest participants have an equal or statistically close probability of being selected.
Unpredictability: The outcome should not be predictable by any party (including adversaries) before a fixed revelation phase.Some additional properties include:
Secrecy (SSLE-specific): The identity of the elected leader remains hidden unless and until they choose to reveal themselves. This prevents pre-emptive attacks, censorship, and bribes.
Censorship Resistance: Because the leader is initially secret, adversaries cannot censor or prevent them from publishing or acting during their window.
Grinding Resistance: Protocols should ensure adversaries cannot increase their odds by trying many inputs (e.g., different randomness, keys).
Further Information
A particularly important refinement of this primitive, introduced in [3], is Single Secret Leader Election (SSLE). In SSLE, the identity of the elected leader remains secret until the leader voluntarily reveals themselves. This is a critical security feature in decentralized settings where public knowledge of leadership could enable censorship, bribery, or denial-of-service attacks. SSLE can be formalised using ideal functionalities in the Universal Composability (UC) framework
References
- Gallager, Robert G., Pierre A. Humblet, and Philip M. Spira. “A distributed algorithm for minimum-weight spanning trees.” ACM Transactions on Programming Languages and systems (TOPLAS) 5, no. 1 (1983): 66-77.
- Korach, Ephraim, Shay Kutten, and Shlomo Moran. “A modular technique for the design of efficient distributed leader finding algorithms.” ACM Transactions on Programming Languages and Systems (TOPLAS) 12, no. 1 (1990): 84-101.
- Boneh, Dan, Saba Eskandarian, Lucjan Hanzlik, and Nicola Greco. “Single secret leader election.” In Proceedings of the 2nd ACM Conference on Advances in Financial Technologies, pp. 12-24. 2020.