TY - GEN

T1 - Fair leader election for rational agents in asynchronous rings and networks

AU - Yifrach, Assaf

AU - Mansour, Yishay

N1 - Publisher Copyright:
© 2018 Copyright held by the owner/author(s). Publication rights licensed to ACM.

PY - 2018/7/23

Y1 - 2018/7/23

N2 - We study a game theoretic model where a coalition of processors might collude to bias the outcome of the protocol, where we assume that the processors always prefer any legitimate outcome over a non-legitimate one. We show that the problems of Fair Leader Election and Fair Coin Toss are equivalent, and focus on Fair Leader Election. Our main focus is on a directed asynchronous ring of n processors, where we investigate the protocol proposed by Abraham et al. [4] and studied in Afek et al. [5]. We show that in general the protocol is resilient only to sub-linear size coalitions. Specifically, we show that Ω(n log n) randomly located processors or Ω(3 n) adversarially located processors can force any outcome. We complement this by showing that the protocol is resilient to any adversarial coalition of size O(4 n). We propose a modification to the protocol, and show that it is resilient to every coalition of size Θ(n), by exhibiting both an attack and a resilience result. For every k ≥ 1, we define a family of graphs Gk that can be simulated by trees where each node in the tree simulates at most k processors. We show that for every graph in Gk, there is no fair leader election protocol that is resilient to coalitions of size k. Our result generalizes a previous result of Abraham et al. [4] that states that for every graph, there is no fair leader election protocol which is resilient to coalitions of size ⌈n 2 ⌉.

AB - We study a game theoretic model where a coalition of processors might collude to bias the outcome of the protocol, where we assume that the processors always prefer any legitimate outcome over a non-legitimate one. We show that the problems of Fair Leader Election and Fair Coin Toss are equivalent, and focus on Fair Leader Election. Our main focus is on a directed asynchronous ring of n processors, where we investigate the protocol proposed by Abraham et al. [4] and studied in Afek et al. [5]. We show that in general the protocol is resilient only to sub-linear size coalitions. Specifically, we show that Ω(n log n) randomly located processors or Ω(3 n) adversarially located processors can force any outcome. We complement this by showing that the protocol is resilient to any adversarial coalition of size O(4 n). We propose a modification to the protocol, and show that it is resilient to every coalition of size Θ(n), by exhibiting both an attack and a resilience result. For every k ≥ 1, we define a family of graphs Gk that can be simulated by trees where each node in the tree simulates at most k processors. We show that for every graph in Gk, there is no fair leader election protocol that is resilient to coalitions of size k. Our result generalizes a previous result of Abraham et al. [4] that states that for every graph, there is no fair leader election protocol which is resilient to coalitions of size ⌈n 2 ⌉.

KW - Asynchronous unidirectional ring

KW - Fair coin toss

KW - Fair leader election

KW - Rational distributed agents

UR - http://www.scopus.com/inward/record.url?scp=85052462313&partnerID=8YFLogxK

U2 - 10.1145/3212734.3212767

DO - 10.1145/3212734.3212767

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AN - SCOPUS:85052462313

SN - 9781450357951

T3 - Proceedings of the Annual ACM Symposium on Principles of Distributed Computing

SP - 217

EP - 226

BT - PODC 2018 - Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing

PB - Association for Computing Machinery

T2 - 37th ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing, PODC 2018

Y2 - 23 July 2018 through 27 July 2018

ER -