Private Information Retrieval Research Papers (original) (raw)

2025

We show the possibility of market crash in rational expectations equi- librium due to information-regime switching. As the equilibrium price of an asset decreases in a smooth way due to adverse demand pressure of noise traders, it reaches a critical value at which the information of uniformed competitive traders changes from partial to full, and causes a discontinuous drop of

2025, arXiv (Cornell University)

This paper presents Wally, a private search system that supports efficient search queries against large databases. When sufficiently many clients are making queries, Wally's performance is significantly better than previous systems while providing a standard privacy guarantee of (ϵ, δ)-differential privacy. Specifically, for a database with 3.2 million entries, Wally's queries per second (QPS) is 7-28x higher, and communication is 6.69-31x smaller than Tiptoe, a state-of-the-art private search system. In Wally, each client adds a few fake queries and sends each query via an anonymous network to the server at independently chosen random instants. We also use somewhat homomorphic encryption (SHE) to reduce the communication size. The number of fake queries each client makes depends inversely on the number of clients making queries. Therefore, the overhead of fake queries vanishes as the number of honest clients increases, enabling scalability to millions of queries and large databases.

2025, The Centre for Market and Public Organisation

To what extent should banks, insurance companies and employers be allowed to use personal information about the people whom they lend to, insure or employ in setting the terms of the contract? Even when different treatment is motivated by profit not prejudice, banning discrimination (when combined with mandatory protection against failure) may well be the best way of effecting redistribution of income. Unlike income taxation this policy achieves its goals without much adverse effect on incentives. Public provision of low-powered incentive contracts issued on generous terms is also a potent instrument of efficient redistribution. This is true even if the government cannot observe type but the private sector can.

2025

2025, Social Science Research Network

We analyze strategic leaks due to spying out a rival's bid in a first-price auction. Such leaks induce sequential bidding, complicated by the fact that the spy may be a counterspy who serves the interests of the spied at bidder and reports strategically distorted information. This ambiguity about the type of spy gives rise to a non-standard signaling problem where both sender and receiver of messages have private information and the sender has a chance to make an unobserved move. Whereas spying without counterspy exclusively benefits the spying bidder, the potential presence of a counterspy yields a collusive outcome, even if the likelihood that the spy is a counterspy is arbitrarily small. That collusive impact shows up in all equilibria and is strongest in the unique pooling equilibrium which is also the payoff dominant equilibrium.

2025, International Journal of Game Theory

We analyze price leadership in a Stackelberg game with incomplete information and imperfect commitment. Sequential play is induced by an information system, represented by a spy, that reports the price of one firm to its rival before the latter chooses its own price. However, the Stackelberg leader may secretly revise its price with some probability. Therefore, the spy’s message is only an imperfect signal. This gives rise to a complex signaling problem where both sender and receiver of messages have private information and the sender has a chance to take another action with some probability. We find partially separating and pooling equilibria that satisfy equilibrium refinements such as the intuitive criterion and support collusive outcomes.

2025

The present paper reconsiders licensing by an inside innovator under incomplete information. Contrary to what was claimed in the literature, the optimal mechanism for non-drastic innovations prescribes royalty rates lower than the cost reduction and generally exhibits fixed fees and exclusion; for drastic innovations fixed-fee contracts are optimal under complete information, whereas under incomplete information, it is optimal to combine state dependent royalty rates with state dependent fixed fees, essentially because linking the license fee to a variable that is correlated with the licensee’s private information tends to lower information rents.

2025, SSRN Electronic Journal

2025, Journal of Business Finance & Accounting

The microstructure literature models the mechanisms through which fundamental information is incorporated into market prices. This paper extends previous models by endogenising information production and analysing incentives for costly information production. In contrast to the existing literature, increasing the number of informed traders can result in reduced price informativeness. When prices have an allocative role this has welfare consequences: the regulatory implications of a dichotomy between private and public incentives for information gathering are discussed.

2025, Journal of Corporate Finance

In the …nancial economics literature debt contracts provide optimal solutions for addressing managerial moral hazard problems. We analyze a model with multiple projects where the manager obtains private information about their quality after the contract with investors is agreed. The likelihood of success of each project depends on both its quality and the level of e¤ort exerted on it by the manager. We …nd distributions of the quality shock such that the optimal …nancial contract requires the investor to hold an equity claim. Our model addresses issues that are relevant for …nancial intermediation and corporate governance.

2025, SSRN Electronic Journal

In the financial economics literature debt contracts provide efficient solutions for addressing managerial moral hazard problems. We analyze a model with multiple projects where the manager obtains private information about their quality after the contract with investors is agreed. The likelihood of success of each project depends on both its quality and the level of effort exerted on it by the manager. We find that, depending on the distribution of the quality shock, the optimal financial contract can be either debt or equity. JEL-Codes: G300, D860.

2025, Wash. ULQ

I. Introduction The source of stockholder gains in going-private transactions has intrigued scholars and public-policy makers since the advent of these transactions in the early 1970s. 1 The social and economic desirability of these... more

2025, Social Science Research Network

for helpful discussions of the ideas in this paper and detailed comments on earlier versions of the manuscript. Ho-Mou Wu helped me write Section 4.4, Eduardo Perez was very helpful in reading the final version of the manuscript and... more

2025, International Journal of Computer Science and Engineering ( IJCSE)

A key cryptographic technique that promotes cooperative computing while protecting data privacy is called Secure Multi-Party Computation (SMPC). SMPC stands out as a strong way to improve security in the cloud computing environment without depending on neural networks or conventional encryption techniques. This study explores the algorithms, mathematical underpinnings, and particular performance metrics of SMPC with a focus on cloud environments. The SMPC design entails clients encrypting their data, which is then collected by cloud servers, decrypted from the aggregated result, and averaged. Details are provided for important methods such homomorphic encryption, secure sum calculation, oblivious transfer, and Shamir's Secret Sharing. Highlighted are the secure multiplication using Beaver triples, Lagrange interpolation for data reconstruction, and the homomorphic characteristics of the Paillier cryptosystem. The study shows how several clients can compute the average of their private data securely using a comprehensive secure data aggregation methodology. According to the research, SMPC protocols are effective and safe, which makes them perfect for cloud-based applications where security and privacy of data are critical considerations. This study emphasises how SMPC can be used to protect private information when working together on cloud computing tasks.

2025, Social Science Research Network

An important theoretical literature motivates collateral as a mechanism that mitigates adverse selection, credit rationing, and other inefficiencies that arise when borrowers hold ex ante private information. There is no clear empirical evidence regarding the central implication of this literature-that a reduction in asymmetric information reduces the incidence of collateral. We exploit exogenous variation in lender information related to the adoption of an information technology that reduces ex ante private information, and compare collateral outcomes before and after adoption. Our results are consistent with this central implication of the private-information models and support the empirical importance of this theory.

2025, Journal of Monetary Economics

and Cheng Wang for helpful comments. All remaining errors are our sole responsibility. The views expressed in this paper are those of the authors and do not necessarily reflect those of the Federal Reserve Bank of Philadelphia or of the... more

2025

This paper examines equilibrium and welfare in a tractable class of economies with externalities, strategic complementarity or substitutability, and incomplete information. In equilibrium, complementarity amplifies aggregate volatility by increasing the sensitivity of actions to public information; substitutability raises cross-sectional dispersion by increasing the sensitivity to private information. To address whether these effects are undesirable from a welfare perspective, we characterize the socially optimal degree of coordination and the efficient use of information. We show how efficient allocations depend on the primitives of the environment, how they compare to equilibrium, and how they can be understood in terms of a social trade-off between volatility and dispersion. We next examine the social value of information in equilibrium. When the equilibrium is efficient, welfare necessarily increases with the accuracy of information; and it increases [decreases] with the extent to which information is common if and only if agents' actions are strategic complements [substitutes]. When the equilibrium is inefficient, additional effects emerge as information affects the gap between equilibrium and efficient allocations. We conclude with a few applications, including production externalities, Keynesian frictions, inefficient fluctuations, and efficient market competition.

2025, The B.E. Journal of Theoretical Economics

We analyse signalling and sorting in a market with frictions and private information. Buyers are heterogeneous, the sellers choose what quality to produce and post prices. Buyers do not observe quality, but infer it from prices. In equilibrium high-quality sellers signal quality with a price that is higher than under perfect information. Compared to the outcome under perfect information the higher price has two effects. First, it makes production of high-quality goods more attractive increasing its supply. Second, it makes high-valuation buyers worse-off, directing part of them to low-quality sellers. We determine which effect dominates; whether too many or too few sellers produce high quality. We also show that the prices of both high- and low-quality goods are higher, and the sellers do better and the buyers worse under private information. In addition, we show that an increase in the production cost of high quality may lead to higher profits and prices.

2025, Social Science Research Network

We report an experimental test of alternative rules in innovation contests when success may not be feasible and contestants may learn from each other. Following Halac et al. (forthcoming), the contest designer can vary the prize allocation rule from Winner-Take-All in which the first successful innovator receives the entire prize to Shared in which all successful innovators during the contest duration share in the prize. The designer can also vary the information disclosure policy from Public in which at each period, all information about contestants' past successes and failures is publicly available, to Private, in which contestants only know their own histories. In our setting, the optimal contest design in terms of maximizing the probability that at least one innovator is successful depends on the probability of successful innovation, given that innovation is feasible. Under some parameters the designer will prefer a WTA-Public contest; while, under others he will prefer Shared-Private. Our experiments provide evidence that Private disclosure contests behaviorally dominate Public disclosure, regardless of the prize allocation rule, and moreover that Shared-Private contests dominate WTA-Private contests.

2025, arXiv (Cornell University)

With a rapidly increasing number of devices connected to the internet, big data has been applied to various domains of human life. Nevertheless, it has also opened new venues for breaching users' privacy. Hence it is highly required to develop techniques that enable data owners to privatize their data while keeping it useful for intended applications. Existing methods, however, do not offer enough flexibility for controlling the utility-privacy trade-off and may incur unfavorable results when privacy requirements are high. To tackle these drawbacks, we propose a compressive-privacy based method, namely RUCA (Ratio Utility and Cost Analysis), which can not only maximize performance for a privacy-insensitive classification task but also minimize the ability of any classifier to infer private information from the data. Experimental results on Census and Human Activity Recognition data sets demonstrate that RUCA significantly outperforms existing privacy preserving data projection techniques for a wide range of privacy pricings.

2025, Journal of Corporate Finance

We investigate how private information in stock prices impacts quarterly dividend changes. We find that the positive relationship between past returns and current dividend changes strengthens when returns convey more private information. This finding is robust to the use of several price informativeness measures and the inclusion of managerial private information and stock overvaluation measures. Managers seem to learn new information from stock prices that they use when deciding on their dividend policy. This study highlights private information in stock prices as an important determinant of dividend policy and contributes to the literature on the real effects of financial markets.

2025, arXiv (Cornell University)

To prevent implicit privacy disclosure in sharing gradients among data owners (DOs) under federated learning (FL), differential privacy (DP) and its variants have become a common practice to offer formal privacy guarantees with low overheads. However, individual DOs generally tend to inject larger DP noises for stronger privacy provisions (which entails severe degradation of model utility), while the curator (i.e., aggregation server) aims to minimize the overall effect of added random noises for satisfactory model performance. To address this conflicting goal, we propose a novel dynamic privacy pricing (DyPP) game which allows DOs to sell individual privacy (by lowering the scale of locally added DP noise) for differentiated economic compensations (offered by the curator), thereby enhancing FL model utility. Considering multidimensional information asymmetry among players (e.g., DO's data distribution and privacy preference, and curator's maximum affordable payment) as well as their varying private information in distinct FL tasks, it is hard to directly attain the Nash equilibrium of the mixed-strategy DyPP game. Alternatively, we devise a fast reinforcement learning algorithm with two layers to quickly learn the optimal mixed noise-saving strategy of DOs and the optimal mixed pricing strategy of the curator without prior knowledge of players' private information. Experiments on real datasets validate the feasibility and effectiveness of the proposed scheme in terms of faster convergence speed and enhanced FL model utility with lower payment costs.

2025, International Journal for Research in Applied Science & Engineering Technology (IJRASET)

Phishing remains one of the most prevalent and evolving cybersecurity threats, exploiting humanvulnerabilities through deceptive digital communication. This study proposes a dynamic, Windows-specific phishing detection model leveraging Random Forest machine learning techniques. By integrating Term Frequency-Inverse Document Frequency (TF-IDF) vectorization with structured email features, the model classifies phishing and legitimate emails with high accuracy. Using secondary data and publicly available datasets, the model achieved a classification accuracy of 98.31% and demonstrated balanced performance across precision, recall, and F1-score metrics. This research underscores the effectiveness of hybrid feature strategies and ensemble learning for phishing detection while outlining key limitations and future directions, including model generalization and real-world deployment readiness.

2025

This paper addresses the question of how public announcements can affect social welfare in an experimental asset market with costly private information acquisition. More specifically, we analyze how public information affects (i) the aggregate profits and (ii) the level of inequality in the distribution of profits across subjects. Using the data of Ruiz-Buforn et al. (2018), we show that public information disclosure always increases aggregate profits, since it crowds out private information reducing the informational costs. Nevertheless, the effects on the level of wealth inequality are ambiguous. They depend on the relative precision of public and private information and, interestingly, on the realization of the public signal. Thus, public information disclosure leads to a trade-off between increasing aggregate profits and reducing the inequality level.

2025

In this paper, we study experimentally the information aggregation process in a market as a function of the access to different sources of information, namely an imperfect, public and costless signal into a market where the participants have access to costly and imperfect private information. Our results show that the release of public information provokes a crowding out effect on the traders' information demand while it keeps constant market informativeness, but significantly reduces price informativeness. Traders overrely on public information, which has a significant negative impact on the overall market performance. We detect the emergence of the overrelying phenomenon, despite the absence of an explicit incentive to the subjects to coordinate, demonstrating, therefore, that the adverse effects of releasing public information in a financial market are more relevant than generally assumed, based on the results of previous experiments inspired by simple coordination models. Ou...

2025, The European Journal of Finance

We conduct laboratory experiments to study whether increasing the number of independent public signals in an economy with endogenous private information is an effective measure to promote the acquisition of information and to enhance price efficiency. We observe that the release of public information crowds out the traders' demand for private information under a single disclosure while favoring private information acquisition under multiple disclosures. The latter measure improves price accuracy in forecasting the asset fundamental value. However, multiple disclosures do not eliminate the adverse effect of market overreaction to public information, becoming a potential source of fragility for the financial system.

2025, Network Theory and Agent-Based Modeling in Economics and Finance

This paper studies the effects on the asset price of the introduction of a public signal in the presence of asymmetric private information in a decentralized market. We introduce an artificial market model populated by boundedly rational agents with heterogeneous levels of reasoning: sophisticated and naive traders. The model captures the main impacts of public information analyzed in the laboratory experiments reported by Ruiz-Buforn et al. (2019). Public information, when correct, coordinates market activity, improving price convergence to the fundamentals. By contrast, unwarranted public information pushes prices away from fundamentals. This strong influence of public information on prices is primarily driven by its common knowledge property.

2025

Las últimas palabras que escribo en esta tesis son para todas esas personas con las que he compartido esta estapa tan importante de mi vida. Una etapa llena de aventuras, alegrías y porqué no, también algunos momentos difíciles. Pero sobre todo, una etapa de descubrimiento y crecimiento personal. En primer lugar me gustaría darles las gracias a mis directores, Simone Alfarano y Eva Camacho Cuena. Gracias por darme la oportunidad de trabajar con vosotros, por vuestros consejos y por transmitirme la pasión por investigar. Por todo lo que he aprendido de vosotros. Vuestro apoyo y confianza me han llevado a descubrir mundo y conocerme un poco más a mí misma. También agradecer a Andrea Morone su participación en esta tesis e invitarme a pasar unos días en la Università Aldo Moro di Bari. I am grateful to Prof. Cars Hommes and other members of Center for Nonlinear Dynamics in Economics and Finance (CeNDEF) for their hospitality during my research visit at the University of Amsterdam in 2017. I would also thank Prof. Douglas D. Davis for allowing me to visit the Commonwealth University in 2018. Thanks for his kindness and advice, and his colleagues from the VCU. Specially, I would like to thank John Lightle for his friendship and the great moments shared with him. I hope our roads cross again. Me gustaría dar la gracias a los miembros del departamento de Economía de la Universitat Jaume I por el buen ambiente, los consejos y las palabras de ánimo sobre todo durante el final de esta etapa. En especial, quiero dar las gracias a mis compañeros y amigos con quienes he compartido cada día de estos años: Isabel, Lidia,

2025, Journal of Banking & Finance

We experimentally study the information aggregation process in a laboratory financial market when a public signal is released. The public disclosure crowds out information demand and reduces price informativeness. The latter effect is primarily caused by the overweighting of public information into prices. We are the first in providing evidence that strategic pricing concerns trigger the overweighting effect and the consequent market overreaction to public disclosures. From an economic policy perspective, we give support that, when deciding their communication strategy, the regulator can mitigate the market overreaction by properly setting the level of information transparency.

2025, Computational Complexity

We show that any 1-round 2-server Private Information Retrieval Protocol where the answers are 1-bit long must ask questions that are at least n -2 bits long, which is nearly equal to the known n -1 upper bound. This improves upon the... more

2025, SSRN Electronic Journal

We study consumption risk sharing when individual income shocks are persistent and not publicly observable, and individuals can default on contracts at the price of financial autarky. We find that, in contrast to a model where the only friction is limited enforcement, our model has observable implications that are similar to those of an Aiyagari (1994) self-insurance model and therefore broadly consistent with empirical observations. However, some of the implied effects of changes in policy or the economic environment are noticeably different in our model compared to self-insurance.

2025, Springer eBooks

We analyse the coarse, the fine, and the private information core allocation of an exchange economy with differential information. The basic questions that we address are whether the above concepts are: (i) coalitionally incentive compatible, i.e., does truthful revelation of information in each coalition occur; and (ii) take into account the information superiority or information advantage of an agent. Moreover, the above three concepts are examined in the presence of externalities and a comparison and interpretation of all of these core notions is provided. We wish to thank Stefan Krasa and Anne Villamil for several useful suggestions. Obviously we are responsible for all errors.

2025, Springer eBooks

The private core of an economy with differential information, (Yannelis (1991)), is the set of all state-wise feasible and private information measurable allocations which cannot be dominated, in terms of ex ante expected utility functions, by state-wise feasible and private information measurable net trades of any coalition. It is coalitionally Bayesian incentive compatible and also takes into account the information superiority of an individual. We provide a noncooperative extensive form interpretation of the private core for three person games. We construct game trees which indicate the sequence of decisions and the information sets, and explain the rules for calculating ex ante expected payoffs. In the spirit of the Nash programme, the private core is thus shown to be supported by the perfect Bayesian equilibrium of a noncooperative game. The discussion contributes not only to the development of ideas but also to the understanding of the dynamics of how coalitionally incentive compatible contracts can be realized.

2025, Economic Theory

proved the existence of a competitive equilibrium for differential information economies with finitely many states. We extend this result to economies with infinitely many states of nature.

2025, Journal of Global Research in Computer Science

Anyone can send a confidential message by just using public information, but the message can only be decrypted with a private key, which is in the sole possession of the intended recipient. It is really appreciable method to provide high security to the medical image or patient's information. Which provide us integrated secure transmission of medical information like Image, Audio, Video etc. with a common key. We also use lossless compression technique like SEQUITUR for efficient utilization of communication channel. The combination of encryption with compression provides confidentiality in the transmission.

2025

Our goal is to elucidate the interaction of banks' screening e¤ort and strategic information production in loan-backed asset markets using a general equilibrium framework. Asset quality is unobserved by investors, but banks may purchase error-prone ratings. The premium paid on highly rated assets emerges as the main determinant of banks' screening e¤ort. The fact that rating strategies re ‡ect banks' private information about asset quality helps keep this premium high. Conventional regulatory policies interfere with this decision margin, thereby reducing signaling value of high ratings and exacerbating the credit misallocation problem. We propose a tax/subsidy scheme that induces e¢ciency.

2025

We investigate the welfare implications of the Miller/Coors joint venture, which merged the second and third largest brewers of beer in the United States. We show that retail prices are stable about a small downward trend for at least seven years prior to the merger but that, four months after the merger, the prices of MillerCoors and Anheuser-Busch Inbev (ABI) increase abruptly by six percent. The prices of more distant substitutes continue at trend. We estimate a structural model and show that emergent tacit collusion between MillerCoors and ABI best explains the data, under reasonable identifying restrictions. Counterfactual simulations indicate that (i) consumer surplus loss from the merger is due to coordination, as merger-specific marginal cost reductions roughly counter-balance changes in unilateral pricing incentives; and (ii) the merger increases total surplus, despite higher retail prices, due to the magnitude of marginal cost reductions.

2025, Social Science Research Network

In this paper we study contracts with two-sided incomplete information. Prior literature on contract remedies does not formally account for the non-breaching party's option to not sue for damages upon breach, when her expected payoff from suing is negative, given the contractual terms and her private information about her post breach loss. With this option incorporated into the analysis, we show that: First, courts should commit to awarding fixed damages, because awarding flexible damages based on ex post information will distort the incentives to breach. This result is not driven by the information forcing effect of basing damages on ex ante expectations, ̀ la Hadley vs. Baxendale. Second, the option of acquiescing to the breach expands the breach set under specific performance, which can be more efficient than other remedies. Third, the efficiency advantage of ex ante expectation damages over ex post actual damages is further enhanced when we account for the possibility of renegotiation. The main results are robust when we account for verification cost of plaintiff's damages and for parties' litigation cost.

2025, RePEc: Research Papers in Economics

In the following paper we analyze the strategic competition between fast and slow traders. The model of Kyle (1985) is adapted to analyze the effect of speed in such a model. A High Frequency Trader (HFT) is defined as a trader that has the ability to react to information faster than other informed traders and as a consequence can trade more than other traders. This trader benefits from low latency compared to slower trader. In such a setting, we prove the existence and the unicity of an equilibrium with fast and slow traders. We find that the speed advantage of High Frequency Traders (HFTs) has a beneficial effect on market liquidity as well as price efficiency. The positive effect on liquidity is present only if there are 2 or more HFTs. However, despite those effects slower traders are at a disadvantage as they are not able to trade on their private information as many times as their HFTs counterpart . When they are able to trade on it, most of their private information has been incorporated into prices due to the latency of HFTs. This implies that slower traders are worse off when HFTs are present. The speed differential benefits HFTs as they earn higher expected profits than their slower counterparts and also benefits liquidity traders. We find the existence of an optimal level of speed for HFT.

2025, SSRN Electronic Journal

In the following paper we analyze the strategic competition between fast and slow traders. A fast or High Frequency Trader (HFT) is defined as a trader that has the ability to react to information faster than other informed traders and as a consequence can trade more than other traders. This trader benefits from low latency compared to slower trader. In such a setting, we prove the existence and the unicity of an equilibrium with fast and slow traders. We find that the speed advantage of HFTs has a beneficial effect on market liquidity as well as price efficiency. The positive effect on liquidity is present only if there are 2 or more HFTs. However, despite those effects slower traders are at a disadvantage as they are not able to trade on their private information as many times as their HFTs counterpart. Once they can, most of their private information has been incorporated into prices due to the lower latency of HFTs. This implies that slower traders are worse off when HFTs are present. The speed differential benefits HFTs as they earn higher expected profits than their slower counterparts and also benefits liquidity traders. We find the existence of an optimal level of speed for HFT.

2025

We study a two-period entry model where the incumbent, privately informed about his cost of production, makes a long run investment choice along with a pricing decision. Investment is costreducing and its effects are assumed to differ across incumbent’s types, as a result investment plays a double role as a commitment variable and, along with price, as a signal. We ask whether and how investment decisions allow the incumbent to limit entry into the market. We find that the incumbent will never undertake strategic investment to deter profitable entry, because when incumbent’s costs are private information the signaling role of investment cancels out its value of commitment.

2025, RePEc: Research Papers in Economics

We obtain a closed-form solution to rational expectations equilibrium with transaction costs in the framework of [On the impossibility of informationally efficient markets. American Economic Review 70, 543-566]. Individual private information incorporated into prices is reduced due to suppressed trading activities by transaction costs. The equilibrium fraction of informed traders increases (decreases) with transaction costs when the costs are low (high). The informativeness of prices decreases with transaction costs.

2025

As computer and other technologies advance and various data and information are pervasively available, preservation of private information embedded in volume data are facing more and more challenges than ever before. Although there are available mechanisms in database management systems limiting access to some sensitive and private information, some inference techniques might still be able to bypass the access control mechanisms to acquire these unauthorized information inappropriately. This paper will propose an active approach to limiting disclosure of sensitive and private information.

2025, arXiv (Cornell University)

We study the problem of weakly private information retrieval (W-PIR), where a user wishes to retrieve a desired message from N non-colluding servers in a way that the privacy leakage regarding the desired message's identity is less than or equal to a threshold. We propose a new code construction which significantly improves upon the best known result in the literature, based on the following critical observation. In previous constructions, for the extreme case of minimum download, the retrieval pattern is to download the message directly from N -1 servers; however this causes leakage to all these N -1 servers, and a better retrieval pattern for this extreme case is to download the message directly from a single server. The proposed code construction allows a natural transition to such a pattern, and for both the maximal leakage metric and the mutual information leakage metric, significant improvements can be obtained. We provide explicit solutions, in contrast to a previous work by Lin et al., where only numerical solutions were obtained.

2025, Journal of Business Ethics

There are two types of stock price manipulation examined in the theoretical literature: 1) insider trading, which involves private information that is true; and 2) the public spreading of fraudulent false information. While there is a large empirical literature on insider trading, this is the first empirical paper to examine the impact of false, fraudulent public information on stock prices and trading volume. We find that such false information, even after being denied by a credible source such as the SEC, generates both abnormal returns and abnormal trading volume. We also find that the effects of the false information on security returns and volume can be persistent for at least two weeks. In addition, we show that perpetrators of false news attacks can make potentially large profits from such market manipulations.

2025, Lecture Notes in Computer Science

Assuming a cryptographically strong cyclic group G of prime order q and a random hash function H, we show that ElGamal encryption with an added Schnorr signature is secure against the adaptive chosen ciphertext attack, in which an attacker can freely use a decryption oracle except for the target ciphertext. We also prove security against the novel one-more-decyption attack. Our security proofs are in a new model, corresponding to a combination of two previously introduced models, the Random Oracle model and the Generic model. The security extends to the distributed threshold version of the scheme. Moreover, we propose a very practical scheme for private information retrieval that is based on blind decryption of ElGamal ciphertexts.

2025, Proceedings of the AAAI Conference on Artificial Intelligence

We study learning statistical properties from strategic agents with private information. In this problem, agents must be incentivized to truthfully reveal their information even when it cannot be directly verified. Moreover, the information reported by the agents must be aggregated into a statistical estimate. We study two fundamental statistical properties: estimating the mean of an unknown Gaussian, and linear regression with Gaussian error. The information of each agent is one point in a Euclidean space.Our main results are two mechanisms for each of these problems which optimally aggregate the information of agents in the truth-telling equilibrium:• A minimal (non-revelation) mechanism for large populations — agents only need to report one value, but that value need not be their point.• A mechanism for small populations that is non-minimal — agents need to answer more than one question.These mechanisms are “informed truthful” mechanisms where reporting unaltered data (truth-tell...

2025, Theory and Decision

In this study, we are concerned with how agents can best amalgamate their private information about a binary state of Nature. The agents are heterogeneous in their "ability", the quality of their private information. The agents cannot directly communicate their private information but instead can only vote between the two states (say "Innocent" or "Guilty" on a criminal jury). We first describe possible methods of sequential majority voting, and then we analyze a particular one: the first n -1 jurors vote simultaneously and, in the case of a tie, the remaining juror has the casting vote. We prove that when n = 3 (a common situation for a tribunal of three judges), the probability of a correct verdict is maximized when the agent of median ability has the casting vote.

2025, Journal of Economic Behavior & Organization

This paper reports the evidence from an experiment which takes advantage of the rich informational structure of the so-called Chinos Game, a traditional parlour game played in many countries. In the experiment subjects receive a binary private signal and have to guess the sum of these signals. We compare two constant-sum versions of the Chinos Game. In one version, which we call Preemption Scenario, the first player who guesses right wins the prize. In the alternative version, called the Copycat Scenario, the last player who guesses right wins the prize. While it is straightforward to see that the Preemption Scenario has a unique and fully revealing equilibrium, in all the equilibria of the Copycat Scenario first movers optimally hide their private information. However, our experimental evidence shows that subjects "lie" in the Copycat Scenario (i.e., systematically distort behavior relative to equilibrium play) and they are successful at doing it, despite that benefits from lying are diminishing as the game proceeds.