Multi-User PIR with Cyclic Wraparound Multi-Access Caches.

We consider the problem of multi-access cache-aided multi-user Private Information Retrieval (MACAMuPIR) with cyclic wraparound cache access. In MACAMuPIR, several files are replicated across multiple servers. There are multiple users and multiple cache nodes. When the network is not congested, servers fill these cache nodes with the content of the files. During peak network traffic, each user accesses several cache nodes. Every user wants to retrieve one file from the servers but does not want the servers to know their demands. This paper proposes a private retrieval scheme for MACAMuPIR and characterizes the transmission cost for multi-access systems with cyclic wraparound cache access. We formalize privacy and correctness constraints and analyze transmission costs. The scheme outperforms the previously known dedicated cache setup, offering efficient and private retrieval. Results demonstrate the effectiveness of the multi-access approach. Our research contributes an efficient, privacy-preserving solution for multi-user PIR, advancing secure data retrieval from distributed servers.

Too Healthy to Fall Sick? Longevity Expectations and Protective Health Behaviours during the First Wave of COVID-19.

Longevity expectations (LE) are subjective assessments of future health status that can influence a number of individual health protective decisions. This is especially true during a pandemic such as COVID-19, as the risk of ill health depends more than ever on such protective decisions. This paper examines the causal effect of LE on some protective health behaviors and a number of decisions regarding forgoing health care using individual differences in LE. We use data from the Survey of Health Ageing and Retirement in Europe, and we draw on an instrumental variable strategy exploiting individual level information on parental age at death. Consistent with the too healthy to be sick hypothesis, we find that individuals, exhibiting higher expected longevity, are more likely to engage in protective behaviours, and are less likely to forgo medical treatment. We estimate that a one standard deviation increase in LE increases the probability to comply always with social distancing by 0.6%, to meet people less often by 0.4% and decreases the probability to forgo any medical treatment by 0.6%. Our estimates vary depending on supply side restrictions influencing the availability of health care, as well as individual characteristics such as their gender and the presence of pre-existing health conditions.

On the Existence of XOR-Based Codes for Private Information Retrieval with Private Side Information.

We consider the problem of Private Information Retrieval with Private Side Information (PIR-PSI), wherein the privacy of the demand and the side information are jointly preserved. Although the capacity of the PIR-PSI setting is known, we observe that the underlying capacity-achieving code construction uses Maximum Distance Separable (MDS) codes therefore contributing to high computational complexity when retrieving the demand. Pointing at this drawback of MDS-based PIR-PSI codes, we propose XOR-based PIR-PSI codes for a simple yet non-trivial setting of two non-colluding databases and two side information files at the user. Although our codes offer substantial reduction in complexity when compared to MDS-based codes, the code-rate marginally falls short of the capacity of the PIR-PSI setting. Nevertheless, we show that our code-rate is strictly higher than that of XOR-based codes for PIR with no side information. As a result, our codes can be useful when privately downloading a file especially after having downloaded a few other messages privately from the same database at an earlier time-instant.

Unique equilibrium in contests with incomplete information.

Considered are imperfectly discriminating contests in which players may possess private information about the primitives of the game, such as the contest technology, valuations of the prize, cost functions, and budget constraints. We find general conditions under which a given contest of incomplete information admits a unique pure-strategy Nash equilibrium. In particular, provided that all players have positive budgets in all states of the world, existence requires only the usual concavity and convexity assumptions. Information structures that satisfy our conditions for uniqueness include independent private valuations, correlated private values, pure common values, and examples of interdependent valuations. The results allow dealing with inactive types, asymmetric equilibria, population uncertainty, and the possibility of resale. It is also shown that any player that is active with positive probability ends up with a positive net rent.

Provably Secure Symmetric Private Information Retrieval with Quantum Cryptography.

Private information retrieval (PIR) is a database query protocol that provides user privacy in that the user can learn a particular entry of the database of his interest but his query would be hidden from the data centre. Symmetric private information retrieval (SPIR) takes PIR further by additionally offering database privacy, where the user cannot learn any additional entries of the database. Unconditionally secure SPIR solutions with multiple databases are known classically, but are unrealistic because they require long shared secret keys between the parties for secure communication and shared randomness in the protocol. Here, we propose using quantum key distribution (QKD) instead for a practical implementation, which can realise both the secure communication and shared randomness requirements. We prove that QKD maintains the security of the SPIR protocol and that it is also secure against any external eavesdropper. We also show how such a classical-quantum system could be implemented practically, using the example of a two-database SPIR protocol with keys generated by measurement device-independent QKD. Through key rate calculations, we show that such an implementation is feasible at the metropolitan level with current QKD technology.

Private information conflict: Lasius niger ants prefer olfactory cues to route memory.

Foraging animals use a variety of information sources to navigate, such as memorised views or odours associated with a goal. Animals frequently use different information sources concurrently, to increase navigation accuracy or reliability. While much research has focussed on conflicts between individually learned (private) information and social information, conflicts between private information sources have been less broadly studied. Here, we investigate such a conflict by pitting route memory against associative odour cue learning in the ant Lasius niger. Ants were alternatingly trained to find a high-quality scented food source on one arm of a Y-maze, and a differently scented low-quality food source on the opposite arm. After training, ants were presented with a Y-maze in which the high- and low-quality-associated scents were presented on opposite arms than during training. The ants showed an extremely strong preferential reliance on the odour cues, with 100% of ants following the high-quality odour and thus moving towards the side associated with low-quality food. Further experiments demonstrated that ants also learn odour associations more rapidly, requiring only one visit to each odour-quality combination to form a reliable association. Side associations in the absence of odours, by contrast, required at least two visits to each side for reliable learning. While much attention has been focussed on visual route learning in insect navigation and decision-making, our results highlight the overwhelming importance of odour cues in insect path choice.

[The Japanese legal system and the applicability of laws and regulations on private information protection and research ethics relating to medical research].

Objectives　To clarify the structure, applicability, and objectives of the current Japanese legislation for private information protection and research ethics and to examine the clauses of the related laws/regulations for academic research purposes.Methods　The research design is a descriptive study based on a systematic literature review. Using the "e-Gov" database, the laws/regulations relating to private information protection and research ethics that apply to medical research involving human subjects and human genome/gene analysis research were included in the research. The Drugs Law (Law No. 145 of 1960) and related GCP/GPSP regulations and laws/regulations on administrative organizations, management, and procedures were excluded. Furthermore, the guidelines and Q&A relating to these laws/regulations and all 47 prefectural regulations on private information protection have been selected from the websites of the related ministries, government organizations, and prefectures.Results　Our study demonstrated that the current legal system on private information protection consists of three layers and that the applicability of the laws/regulations in this area varies according to the type of research organization. Additionally, the applicability of the laws/regulations on research ethics is different depending on the research area. While the Private Information Protection Law (PIPL) for the private sector contains two objectives, PIPL for administrative organizations and PIPL for independent administrative organizations both include three objectives. For academic research purposes, PIPL for the private sector sets out a holistic exemption clause, whereas the other two PIPLs stipulate three specific exemption clauses. Furthermore, our research revealed that the clauses of the prefectural regulations demonstrated many variances.Conclusion　This study suggests that the current Japanese legal system relating to private information protection could be defined as a "mixed model," wherein the laws/regulations concerned are not necessarily consistent. The protection of medical information is solely regulated by a few specific laws with a narrow scope of application; the ethical guidelines are not directly based on any laws; and identifying applicable laws/regulations, depending on the category of research organization, is complicated, especially in the case of collaborative research involving researchers from various organizations. Therefore, in the larger framework of legislation, it is indispensable to reconsider the protection of private medical information and its effective use, including the ethics of this process because of the sensitive and useful nature of private medical information.

Advantageous Selection, Moral Hazard, and Insurer Sorting on Risk in the U.S. Automobile Insurance Market.

This study quantifies the role of private information in automobile insurance policy choice using data on subjective beliefs, risk preference, reckless driving, the respondent's insurer and insurance policy characteristics merged with insurer-specific quality ratings distributed by independent organizations. We find a zero correlation between ex post accident risk and insurance coverage, reflecting advantageous selection in policy choice offset by moral hazard. Advantageous selection is partly attributable to insurer sorting on consumer attributes known and used by insurers. Our analysis of insurer sorting reveals that lower-risk drivers on attributes observed by insurers obtain coverage from insurers with higher-quality ratings.

A solution for private assessment in indirect reciprocity using solitary observation.

Although indirect reciprocity is a fundamental mechanism in the evolution of human cooperation, most studies assume public assessment in which individuals are not permitted to obtain private assessments of others. Existing studies on private assessment have used individual-based simulations because of the analytical difficulty involved. Here, we develop an analytical method using solitary observation to solve private assessment in indirect reciprocity problem without any approximation. In this study, we formulate a model of solitary observation and calculate the replicator dynamics systems of five leading norms of indirect reciprocity. Indirect reciprocity in private assessment provides a different result to that in public assessment. According to the existence proofs of cooperative evolutionarily stable (CES) points in the system, strict norms (stern judging and shunning) have no CES point in private assessment, while they do in public assessment. Image scoring does not change the system regardless of the assessment types because it does not use second-order information. In tolerant norms (simple standing and staying), the CES points move to co-existence of norms and unconditional cooperators. Despite the fact that there is no central coercive assessment system in private assessment, the average cooperation rate at the CES points in private assessment is greater than that in public assessment. This is because private assessment gives unconditional cooperators a role. Our results also show the superiority of the staying norm. Compared with simple standing, staying has three advantages in private assessment: a higher cooperation rate, easiness of invasion into defectors, and robustness to maintain cooperative evolutionarily stable situations. Our results are applicable to general social dilemmas in relation to private information. Under some dilemmas, norms or assessment rules should be carefully chosen to enable cooperation to evolve.

Efficient and secure outsourcing of genomic data storage.

BACKGROUND: Cloud computing is becoming the preferred solution for efficiently dealing with the increasing amount of genomic data. Yet, outsourcing storage and processing sensitive information, such as genomic data, comes with important concerns related to privacy and security. This calls for new sophisticated techniques that ensure data protection from untrusted cloud providers and that still enable researchers to obtain useful information. METHODS: We present a novel privacy-preserving algorithm for fully outsourcing the storage of large genomic data files to a public cloud and enabling researchers to efficiently search for variants of interest. In order to protect data and query confidentiality from possible leakage, our solution exploits optimal encoding for genomic variants and combines it with homomorphic encryption and private information retrieval. Our proposed algorithm is implemented in C++ and was evaluated on real data as part of the 2016 iDash Genome Privacy-Protection Challenge. RESULTS: Results show that our solution outperforms the state-of-the-art solutions and enables researchers to search over millions of encrypted variants in a few seconds. CONCLUSIONS: As opposed to prior beliefs that sophisticated privacy-enhancing technologies (PETs) are unpractical for real operational settings, our solution demonstrates that, in the case of genomic data, PETs are very efficient enablers.

Dominance and social information use in a lizard.

There is mounting evidence that social learning is not just restricted to group-living animals, but also occurs in species with a wide range of social systems. However, we still have a poor understanding of the factors driving individual differences in social information use. We investigated the effects of relative dominance on social information use in the eastern water skink (Eulamprus quoyii), a species with age-dependent social learning. We used staged contests to establish dominant-subordinate relationships in pairs of lizards and tested whether observers use social information to more quickly solve both an association and reversal learning task in situations where the demonstrator was either dominant or subordinate. Surprisingly, we found no evidence of social information use, irrespective of relative dominance between observer and demonstrator. However, dominant lizards learnt at a faster rate than subordinate lizards in the associative learning task, although there were no significant differences in the reversal task. In light of previous work in this species, we suggest that age may be a more important driver of social information use because demonstrators and observers in our study were closely size-matched and were likely to be of similar age.

Generating unique IDs from patient identification data using security models.

BACKGROUND: The use of electronic health records (EHRs) has continued to increase within healthcare systems in the developed and developing nations. EHRs allow for increased patient safety, grant patients easier access to their medical records, and offer a wealth of data to researchers. However, various bioethical, financial, logistical, and information security considerations must be addressed while transitioning to an EHR system. The need to encrypt private patient information for data sharing is one of the foremost challenges faced by health information technology. METHOD: We describe the usage of the message digest-5 (MD5) and secure hashing algorithm (SHA) as methods for encrypting electronic medical data. In particular, we present an application of the MD5 and SHA-1 algorithms in encrypting a composite message from private patient information. RESULTS: The results show that the composite message can be used to create a unique one-way encrypted ID per patient record that can be used for data sharing. CONCLUSION: The described software tool can be used to share patient EMRs between practitioners without revealing patients identifiable data.

Private Information and Insurance Rejections.

Across a wide set of non-group insurance markets, applicants are rejected based on observable, often high-risk, characteristics. This paper argues that private information, held by the potential applicant pool, explains rejections. I formulate this argument by developing and testing a model in which agents may have private information about their risk. I first derive a new no-trade result that theoretically explains how private information could cause rejections. I then develop a new empirical methodology to test whether this no-trade condition can explain rejections. The methodology uses subjective probability elicitations as noisy measures of agents beliefs. I apply this approach to three non-group markets: long-term care, disability, and life insurance. Consistent with the predictions of the theory, in all three settings I find significant amounts of private information held by those who would be rejected; I find generally more private information for those who would be rejected relative to those who can purchase insurance; and I show it is enough private information to explain a complete absence of trade for those who would be rejected. The results suggest private information prevents the existence of large segments of these three major insurance markets.

Sexually transmitted infections with semi-anonymous matching.

We analyze the spread of sexually transmitted infections in an environment where individuals search for a sexual partner and, when found, cannot verify whether his partner is infected. Decisions are based on a variety of factors including the proportion infected, the likelihood of safe sex, the rate of detection and treatment, the cost of infection, and the length of search. The model demonstrates how directed search induces a separating equilibrium and, as a result, supports empirical evidence demonstrating the importance of sero-sorting. Furthermore, the model reinforces arguments that decreasing the costs of infection increases the infection rate. The model is calibrated, and the policy implications are analyzed within the context of men who have sex with men.