Dicey Games: Shared Sources of Randomness in Distributed Systems
Pith reviewed 2026-05-16 11:19 UTC · model grok-4.3
The pith
In the four-player Matching Pennies game, a team using only pairwise shared randomness sources can win with probability strictly above one quarter.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Dicey Games formalize team-versus-adversary games in which coordination occurs solely through an allocation of shared randomness sources; for the concrete 4-player Matching Pennies instance, pairwise sharing already yields a win probability strictly greater than 1/4, and the framework supplies existence, representation, and complexity results for optimal strategies under arbitrary allocations.
What carries the argument
Dicey Games, the model in which a team’s coordination graph determines which subsets of players share independent randomness sources, and optimal mixed strategies are computed over the resulting joint distributions.
If this is right
- Optimal strategies exist for any finite Dicey Game and any allocation of shared sources.
- Optimal strategies admit a finite-support representation whose size is bounded by the number of players and sources.
- Finding an optimal strategy is computationally hard in general, but polynomial for fixed numbers of players.
- Given a budget of randomness sources, the problem of choosing the best allocation can be solved by enumeration over graphs.
Where Pith is reading between the lines
- The same pairwise-sharing pattern may improve coordination in other simultaneous-move distributed protocols that already use limited shared randomness.
- Extending the model to sequential games or noisy channels would test whether the >1/4 threshold generalizes.
- Concrete small instances could be implemented on hardware with limited entanglement or shared seeds to measure empirical gains.
Load-bearing premise
The team’s only coordination mechanism is the pre-assigned shared randomness sources; all choices are made simultaneously with no further communication.
What would settle it
An explicit calculation or linear-program solution for the 4-player Matching Pennies instance that reports a maximum win probability of at most 1/4 when each pair of teammates shares one private random bit.
Figures
read the original abstract
Consider a 4-player version of Matching Pennies where a team of three players competes against the Devil. Each player simultaneously says "Heads" or "Tails". The team wins if all four choices match; otherwise the Devil wins. If all team players randomise independently, they win with probability 1/8; if all players share a common source of randomness, they win with probability 1/2. What happens when each pair of team players shares a source of randomness? Can the team do better than win with probability 1/4? The surprising (and nontrivial) answer is yes! We introduce Dicey Games, a formal framework motivated by the study of distributed systems with shared sources of randomness (of which the above example is a specific instance). We characterise the existence, representation and computational complexity of optimal strategies in Dicey Games, and we study the problem of allocating limited sources of randomness optimally within a team.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces Dicey Games, a formal framework for distributed systems in which agents coordinate via allocated shared randomness sources. It analyzes a 4-player Matching Pennies instance in which a team of three players faces the Devil, showing that pairwise shared randomness sources allow the team to win with probability strictly greater than 1/4 (compared with 1/8 for independent randomness and 1/2 for a single shared source). The authors characterize existence, representation, and computational complexity of optimal strategies within the framework and study the problem of optimally allocating a limited number of randomness sources among team members.
Significance. If the characterizations hold, the work supplies a new, self-contained model for reasoning about partial coordination in distributed systems, with direct relevance to multi-agent game theory and distributed computing. The concrete demonstration that pairwise sharing exceeds the 1/4 threshold is nontrivial and falsifiable. The paper provides explicit characterizations of optimal strategies together with complexity results, which constitute a reusable technical contribution.
major comments (2)
- [§3.2] §3.2, the explicit strategy for the pairwise-sharing case: the claimed winning probability >1/4 is stated but the derivation of the exact value and the verification that it is optimal are not cross-referenced to the general representation theorem in §4.1; without this link the central claim rests on an unverified calculation.
- [§5] §5, the complexity result for optimal allocation: the reduction establishing NP-completeness assumes that the number of randomness sources is part of the input, yet the paper does not discuss whether the hardness persists when the number of sources is fixed (a regime relevant to the motivating example).
minor comments (2)
- [Abstract] The abstract asserts a 'surprising (and nontrivial) answer is yes' but does not state the concrete probability achieved by the pairwise strategy; adding this value would improve readability.
- [§2] Notation for the shared-randomness graph (vertices = players, edges = shared sources) is introduced without a small illustrative diagram; a figure would clarify the pairwise-sharing configuration used in the main example.
Simulated Author's Rebuttal
We thank the referee for the positive evaluation and the precise comments. We address each major point below and will revise the manuscript accordingly.
read point-by-point responses
-
Referee: [§3.2] §3.2, the explicit strategy for the pairwise-sharing case: the claimed winning probability >1/4 is stated but the derivation of the exact value and the verification that it is optimal are not cross-referenced to the general representation theorem in §4.1; without this link the central claim rests on an unverified calculation.
Authors: We agree that an explicit link is needed. In the revised version we will add a direct cross-reference from §3.2 to the representation theorem in §4.1, together with a short derivation showing how the pairwise strategy yields a winning probability strictly greater than 1/4 and confirming optimality via the general result. revision: yes
-
Referee: [§5] §5, the complexity result for optimal allocation: the reduction establishing NP-completeness assumes that the number of randomness sources is part of the input, yet the paper does not discuss whether the hardness persists when the number of sources is fixed (a regime relevant to the motivating example).
Authors: The referee is correct that the reduction treats the number of sources as part of the input. We will add a short discussion in §5 noting that, for any fixed constant number of sources, all possible allocations can be enumerated in polynomial time (though evaluating the value of each allocation remains hard); this regime is directly relevant to the 4-player motivating example. revision: yes
Circularity Check
No significant circularity detected in derivation chain
full rationale
The paper introduces Dicey Games as a new formal framework for modeling distributed systems with shared randomness sources, using the 4-player Matching Pennies example to illustrate that pairwise shared randomness yields win probability strictly above 1/4. It then characterizes existence, representation, and computational complexity of optimal strategies within this framework. No equations, fitted parameters, or self-citations are visible that reduce any claimed result to its own inputs by construction; the central claims rest on the newly defined model and its internal analysis rather than self-definitional loops, renamed empirical patterns, or load-bearing prior self-citations. The derivation is therefore self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Players choose simultaneously and payoffs depend only on the tuple of choices.
invented entities (1)
-
Dicey Games
no independent evidence
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We introduce Dicey Games, a formal framework... characterise the existence, representation and computational complexity of optimal strategies
-
IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Theorem 3.7... k-grid strategy... Theorem 4.2... finite representation whose bit-size grows exponentially
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Forward citations
Cited by 1 Pith paper
-
Randomise Alone, Reach as a Team
In concurrent graph games with distributed private randomness, memoryless strategies decide threshold reachability (NP-hard) and almost-sure reachability is NP-complete; IRATL extends ATL for probability thresholds wi...
Reference graph
Works this paper leans on
-
[1]
Alessandro Abate, Julian Gutierrez, Lewis Hammond, Paul Harrenstein, Marta Kwiatkowska, Muhammad Najib, Giuseppe Perelli, Thomas Steeples, and Michael J. Wooldridge. 2021. Rational verification: game-theoretic verification of multi-agent systems.Appl. Intell.51, 9 (2021), 6569–6584. doi:10.1007/S10489- 021-02658-Y
-
[2]
Ricardo Alonso and Odilon Câmara. 2016. Persuading voters.American Economic Review106, 11 (2016), 3590–3605
work page 2016
-
[3]
Robert J. Aumann. 1974. Subjectivity and correlation in randomized strategies. Journal of Mathematical Economics1, 1 (1974), 67–96. doi:10.1016/0304-4068(74) 90037-8
-
[4]
Robert J Aumann. 1974. Subjectivity and correlation in randomized strategies. Journal of mathematical economics1, 1 (1974), 67–96
work page 1974
-
[5]
R. J. Aumann and J. H. Dreze. 1974. Cooperative games with coalition structures. Int. J. Game Theory3, 4 (Dec. 1974), 217–237. doi:10.1007/BF01766876
-
[6]
Saugata Basu, Richard Pollack, and Marie-Françoise Roy. 1994. On the Com- binatorial and Algebraic Complexity of Quantifier Elimination. InFOCS. IEEE Computer Society, 632–641. doi:10.1109/SFCS.1994.365728
-
[7]
Saugata Basu, Richard Pollack, and Marie-Françoise Roy. 1996. On the combi- natorial and algebraic complexity of quantifier elimination.Journal of the ACM (JACM)43, 6 (1996), 1002–1045
work page 1996
-
[8]
Saugata Basu, Richard Pollack, and Marie-Françoise Roy. 1997. On Computing a Set of Points Meeting Every Cell Defined by a Family of Polynomials on a Variety. Journal of Complexity13, 1 (1997), 28–37. doi:10.1006/jcom.1997.0434
-
[9]
2006.Algorithms in Real Algebraic Geometry(2nd ed.)
Saugata Basu, Richard Pollack, and Marie-Françoise Roy. 2006.Algorithms in Real Algebraic Geometry(2nd ed.). Springer. doi:10.1007/978-3-540-30140-0
-
[10]
Mokhtar S. Bazaraa, Hanif D. Sherali, and C. M. Shetty. 2006.Nonlinear Pro- gramming: Theory and Algorithms(3rd ed.). John Wiley & Sons, Hoboken, New Jersey
work page 2006
-
[11]
Mihir Bellare, Wei Dai, and Phillip Rogaway. 2020. Reimagining Secret Sharing: Creating a Safer and More Versatile Primitive by Adding Authenticity, Correcting Errors, and Reducing Randomness Requirements. InProceedings on Privacy En- hancing Technologies (PoPETs), Vol. 2020. 461–490. doi:10.2478/popets-2020-0081
-
[12]
Dirk Bergemann and Stephen Morris. 2016. Bayes correlated equilibrium and the comparison of information structures in games.Theoretical Economics11, 2 (2016), 487–522
work page 2016
-
[13]
Dirk Bergemann and Stephen Morris. 2019. Information design: A unified per- spective.Journal of Economic Literature57, 1 (2019), 44–95
work page 2019
-
[14]
Markus Bläser, Julian Dörfler, Maciej Liśkiewicz, and Benito van der Zander. 2024. The Existential Theory of the Reals with Summation Operators. InISAAC 2024 (LIPIcs, Vol. 322). Schloss Dagstuhl – Leibniz-Zentrum für Informatik, 13:1–13:19. doi:10.4230/LIPIcs.ISAAC.2024.13
-
[15]
Florian Brandl, Felix Brandt, and Hans Georg Seedig. 2016. Consistent probabilis- tic social choice.Econometrica84, 5 (2016), 1839–1880. doi:10.3982/ECTA13322
-
[16]
Felix Brandt. 2019. Collective choice lotteries. InStudies in Economic Design. Springer, 51–73. doi:10.1007/978-3-030-18050-8_9
-
[17]
Eric Budish, Yeon-Koo Che, Fuhito Kojima, and Paul Milgrom. 2013. Designing random allocation mechanisms: Theory and applications.American Economic Review103, 2 (2013), 585–623. doi:10.1257/aer.103.2.585
-
[18]
George E. Collins. 1974. Quantifier elimination for real closed fields by cylindrical algebraic decomposition–preliminary report.SIGSAM Bull.8, 3 (Aug. 1974), 80–90. doi:10.1145/1086837.1086852
-
[19]
1838.Recherches sur les principes mathématiques de la théorie des richesses
Antoine Augustin Cournot. 1838.Recherches sur les principes mathématiques de la théorie des richesses. L. Hachette, Paris. English trans: Researches into the Mathematical Principles of the Theory of Wealth (1897)
-
[20]
Leonardo de Moura and Nikolaj Bjørner. 2008. Z3: an efficient SMT solver. Tools and Algorithms for the Construction and Analysis of Systems4963, 337–340. doi:10.1007/978-3-540-78800-3_24
-
[21]
Yossi Gilad, Rotem Hemo, Silvio Micali, Georgios Vlachos, and Nickolai Zel- dovich. 2017. Algorand: Scaling Byzantine Agreements for Cryptocurrencies. InProceedings of the 26th Symposium on Operating Systems Principles (SOSP ’17). ACM, 51–68. doi:10.1145/3132747.3132757
-
[22]
2010.A Primer on Pseudorandom Generators
Oded Goldreich. 2010.A Primer on Pseudorandom Generators. University Lecture Series, Vol. 55. American Mathematical Society. doi:10.1090/ulect/055
-
[23]
Friedrich August Hayek. 1945. The use of knowledge in society.The American economic review35, 4 (1945), 519–530
work page 1945
-
[24]
J.V Howard. 1992. A social choice rule and its implementation in perfect equi- librium.Journal of Economic Theory56, 1 (1992), 142–159. doi:10.1016/0022- 0531(92)90073-Q
-
[25]
Fritz John. 1948. Extremum Problems with Inequalities as Subsidiary Conditions. InStudies and Essays Presented to R. Courant on his 60th Birthday, K. O. Friedrichs, O. E. Neugebauer, and J. J. Stoker (Eds.). Interscience Publishers, New York, 187–204
work page 1948
-
[26]
Kai-Uwe Kühn. 2001. Fighting collusion–Regulation of communication between competitors.Economic Policy16, 32 (2001), 168–204
work page 2001
-
[27]
Marta Kwiatkowska, Gethin Norman, David Parker, and Gabriel Santos. 2018. Equilibria-based Probabilistic Model Checking for Concurrent Stochastic Games. Formal Methods in System Design53, 3 (2018), 261–294
work page 2018
-
[28]
I. E. Leonard and J. E. Lewis. 2016.Geometry of Convex Sets(1st ed.). Wiley- Blackwell, Hoboken, New Jersey, United States. 336 pages
work page 2016
-
[29]
Mangasarian and Stan Fromovitz
Olvi L. Mangasarian and Stan Fromovitz. 1967. The Fritz John Necessary Op- timality Conditions in the Presence of Equality and Inequality Constraints.J. Math. Anal. Appl.17, 1 (1967), 37–47. doi:10.1016/0022-247X(67)90163-1
- [30]
-
[31]
Saptarshi Mukherjee and Hans Peters. 2022. Self-implementation of social choice correspondences in Nash equilibrium.Social Choice and Welfare59, 4 (November 2022), 1009–1028. doi:10.1007/s00355-022-01420-8
-
[32]
Roger B. Myerson. 1999. Nash Equilibrium and the History of Economic Theory. Journal of Economic Literature37, 3 (September 1999), 1067–1082
work page 1999
-
[33]
John F. Nash. 1950. Equilibrium points in 𝑛-person games.Proceedings of the National Academy of Sciences36, 1 (1950), 48–49. doi:10.1073/pnas.36.1.48
-
[34]
Marcus Schaefer. 2013. Realizability of Graphs and Linkages. 461-482 pages. doi:10.1007/978-1-4614-0110-0_24
-
[35]
Gustavus J. Simmons. 1984. The Prisoners’ Problem and the Subliminal Channel. InAdvances in Cryptology, Proceedings of CRYPTO ’83 (Lecture Notes in Computer Science, Vol. 196). Springer, 51–67. doi:10.1007/978-1-4684-4730-9_5
-
[36]
Ewa Syta, Philipp Jovanovic, Eleftherios Kokoris-Kogias, Nicolas Gailly, Linus Gasser, Ismail Khoffi, Michael J. Fischer, and Bryan Ford. 2017. Scalable Bias- Resistant Distributed Randomness. In2017 IEEE Symposium on Security and Privacy (SP). IEEE, 444–460. doi:10.1109/SP.2017.34
-
[37]
2010.Stochastic multiplayer games: theory and algorithms
Michael Ummels. 2010.Stochastic multiplayer games: theory and algorithms. Ph. D. Dissertation. RWTH Aachen, Germany
work page 2010
-
[38]
2010.Information and learning in markets: the impact of market microstructure
Xavier Vives. 2010.Information and learning in markets: the impact of market microstructure. Princeton University Press
work page 2010
-
[39]
1944.Theory of Games and Economic Behavior
John von Neumann and Oskar Morgenstern. 1944.Theory of Games and Economic Behavior. Princeton University Press, Princeton, NJ. A Useful theorems We state here some geometry theorems that we use in our proofs. Note that, in the references cited, the theorem that is proven is often more general: we state it here in a form that fits our purposes. Theorem A.1...
work page 1944
-
[40]
(1−𝑏 ℭ 11) +𝜆 1𝜆2 (1−𝜆 3) (1−𝑏 𝔄
-
[41]
(1−𝑏 ℭ 12) +𝜆 1 (1−𝜆 2)𝜆3 (1−𝑏 𝔄
-
[42]
(1−𝑏 ℭ 11) +𝜆 1 (1−𝜆 2) (1−𝜆 3) (1−𝑏 𝔄
-
[43]
(1−𝑏 ℭ 12) + (1−𝜆 1)𝜆2𝜆3 (1−𝑏 𝔄
-
[44]
(1−𝑏 ℭ 21) + (1−𝜆 1)𝜆2 (1−𝜆 3) (1−𝑏 𝔄
-
[45]
(1−𝑏 ℭ 22) + (1−𝜆 1) (1−𝜆 2)𝜆3 (1−𝑏 𝔄
-
[46]
(1−𝑏 ℭ 21) + (1−𝜆 1) (1−𝜆 2) (1−𝜆 3) (1−𝑏 𝔄
-
[47]
(1−𝑏 ℭ 22) (8) ∀𝑖∈ {1,2,3},0≤𝜆 𝑖 ≤1(9) C Proof of Theorem 3.7 Theorem 3.7(App. C).Let D be a dicey game. Let 𝑘 be the number of actions available for the Devil. Then, for every collective strategy, there exists a𝑘-grid strategy whose value is at least as large. Proof. This proof follows the structure of that of Lemma 3.3 and generalises it: it first defin...
work page 2017
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.