Blockchain Papers

Lin Chen, Tongzhou Qu, Anqi Yin

No abstract is available for this record.

Zijian Zhang, Xin Lü, Meng Li, Jincheng An · 10 authors

The sealed-bid auction enables bidders to secretly send their bids to the auctioneer, which compares all bids and publishes the winning one on the bid-opening day. This type of auction is friendly for protecting the bid privacy, and sufficiently fair for all bidders if the auctioneer acts faithfully. Unfortunately, the auctioneer may not always be trustworthy. The auctioneer has the ability to deliberately leak any bid information to a part of bidders for raising the final winning price based on the investigation. Meanwhile, the auctioneer can appoint any bidder as the winner, as long as the bidder accepts a higher winning price than the current highest bid. Since bidders cannot obtain any bid information from others, to the best of our knowledge, it is difficult to prevent bid leakage from the auctioneer, and support bidders to verify the bid comparison results without disclosing the winning bid, simultaneously. To alleviate these problems, we first construct a homomorphic encryption(HE)-based bid comparison circuit. All bidders can directly compute a cipher of the winning bid by using this circuit; hence, the winning bid does not need to be exposed to all bidders. Then, we propose a blockchain-based sealed-bid scheme (BSS) by integrating the circuit with commitment and zero-knowledge proof. The auctioneer only obtains the commitments of bids before the bid-opening day, and he has to prove that the winner's bid is the same as the plaintext of the bidders' computed cipher. Thus, the auctioneer can neither leak the bid information nor publish a higher winning price during in the auction. Detailed performance analysis shows that the computational complexity of BSS is linear with the binary length of bids.

Marta Irene García Cid, Dileepsai Bodanapu, Alberto Gatto, Paolo Martelli · 6 authors

A new interactive quantum zero-knowledge protocol for identity authentication implementable in currently available quantum cryptographic devices is proposed and demonstrated. The protocol design involves a verifier and a prover knowing a pre-shared secret, and the acceptance or rejection of the proof is determined by the quantum bit error rate. It has been implemented in modified Quantum Key Distribution devices executing two fundamental cases. In the first case, all players are honest, while in the second case, one of the users is a malicious player. We demonstrate an increase of the quantum bit error rate around 25% in the latter case compared to the case of honesty. The protocol has also been validated for distances from a back-to-back setup to more than 60 km between verifier and prover. The security and robustness of the protocol has been analysed, demonstrating its completeness, soundness and zero-knowledge properties.

S. Sivasankari, Deepak K. Gupta, Ismail Keshta, Ch. Venkata Krishna Reddy · 6 authors

No abstract is available for this record.

Andrea Flamini, Giada Sciarretta, Mario Scuro, Amir Sharif · 6 authors

Verifiable credentials are a digital analogue of physical credentials. Their authenticity and integrity are protected by means of cryptographic techniques, and they can be presented to verifiers to reveal attributes or even predicates about the attributes included in the credential. One way to preserve privacy during presentation consists in selectively disclosing the attributes in a credential. In this paper we present the most widespread cryptographic mechanisms used to enable selective disclosure of attributes identifying two categories: the ones based on hiding commitments - e.g., mdl ISO/IEC 18013-5 - and the ones based on non-interactive zero-knowledge proofs - e.g., BBS signatures. We also include a description of the cryptographic primitives used to design such cryptographic mechanisms. We describe the design of the cryptographic mechanisms and compare them by performing an analysis on their standard maturity in terms of standardization, cryptographic agility and quantum safety, then we compare the features that they support with main focus on the unlinkability of presentations, the ability to create predicate proofs and support for threshold credential issuance. Finally we perform an experimental evaluation based on the Rust open source implementations that we have considered most relevant. In particular we evaluate the size of credentials and presentations built using different cryptographic mechanisms and the time needed to generate and verify them. We also highlight some trade-offs that must be considered in the instantiation of the cryptographic mechanisms.

Yonghua Zhan, Feng Yuan, Rui Shi, Guozhen Shi · 5 authors

Electronic tickets (e-tickets) are gradually being adopted as a substitute for paper-based tickets to bring convenience to customers, corporations, and governments. However, their adoption faces a number of practical challenges, such as flexibility, privacy, secure storage, and inability to deploy on IoT devices such as smartphones. These concerns motivate the current research on e-ticket systems, which seeks to ensure the unforgeability and authenticity of e-tickets while simultaneously protecting user privacy. Many existing schemes cannot fully satisfy all these requirements. To improve on the current state-of-the-art solutions, this paper constructs a blockchain-enhanced privacy-preserving e-ticket system for IoT devices, dubbed PriTKT, which is based on blockchain, structure-preserving signatures (SPS), unlinkable redactable signatures (URS), and zero-knowledge proofs (ZKP). It supports flexible policy-based ticket purchasing and ensures user unlinkability. According to the data minimization and revealing principle of GDPR, PriTKT empowers users to selectively disclose subsets of (necessary) attributes to sellers as long as the disclosed attributes satisfy ticket purchasing policies. In addition, benefiting from the decentralization and immutability of blockchain, effective detection and efficient tracing of double spending of e-tickets are supported in PriTKT. Considering the impracticality of existing e-tickets schemes with burdensome ZKPs, we replace them with URS/SPS or efficient ZKP to significantly improve the efficiency of ticket issuing and make it suitable for use on smartphones.

Wezi Bonono Chipeta, Abdullahi Adaviriku Malik

Blockchain technology offers a promising way to improve business processes by providing a secure and transparent transaction platform. However, using this technology brings its own set of challenges, especially when trying to balance user privacy with legal and regulatory needs. This article explores the challenges of keeping user information private, adhering to regulatory frameworks, and fulfilling legal requirements on the blockchain. A key point in this research is the challenge of keeping or maintaining confidentiality while being transparent. The article also discusses the issues of applying legal rules to a system not controlled by one central authority, the risks of privacy and security breaches, and the need to follow data protection laws. The article highlights how some blockchain-based companies have tackled these challenges, mainly through smart blockchain management and innovative technology, by looking at real-world examples from major companies like IBM, Bitpay, Ripple, and Coinbase. The systematic literature review (SLR) methodology involved reviewing literature from the past 15 years (2008-2023) from trusted sources like Google Scholar, ACM Digital Library, IEEE, Springer, and Science Direct. The findings indicate that cutting-edge technologies prioritizing privacy, such as zero-knowledge proofs, ring signatures, and encryption methods, would enable Bitcoin (BTC) platform operations to maintain or balance privacy and transparency. Furthermore, the study indicates the importance of clear privacy guidelines, adhering to relevant regulations, working closely with regulators and law enforcement, and educating users. In summary, it is crucial to approach blockchain carefully, prioritizing user privacy while meeting all legal and regulatory requirements.

Wooyoung Son, Soonhong Kwon, Sung-Heun Oh, Jong‐Hyouk Lee

As the demand and diversity of digital content increase, consumers now have simple and easy access to digital content through Over-the-Top (OTT) services. However, the rights of copyright holders remain unsecured due to issues with illegal copying and distribution of digital content, along with unclear practices in copyright royalty settlements and distributions. In response, this paper proposes an automated OTT service copyright distribution management system using the Open Digital Rights Language (ODRL) to safeguard the rights of copyright holders in the OTT service field. The proposed system ensures that the rights to exercise copyright transactions and agreements, such as trading of copyright, can only be carried out when all copyright holders of a single digital content agree based on the Threshold Schnorr Digital Signature. This approach takes into account multiple joint copyright holders, thereby safeguarding their rights. Furthermore, it ensures fair and transparent distribution of copyright royalties based on the ratio information outlined in ODRL. From the user’s perspective, the system not only provides services proactively based on the rights information specified in ODRL, but also employs zero-knowledge proof technology to handle sensitive information in OTT service copyright distribution, thereby addressing existing privacy concerns. This approach not only considers joint copyright holders, but also demonstrates its effectiveness in resolving prevalent issues in current OTT services, such as illegal digital content replication and distribution, and the unfair settlement and distribution of copyright royalties. Applying this proposed system to the existing OTT services and digital content market is expected to lead to the revitalization of the digital content trading market and the establishment of an OTT service environment that guarantees both vitality and reliability.

Xi Luo, Hepeng Jia, Jingjie Qian

The COVID-19 pandemic reveals an obvious ideological influence on people’s health decisions worldwide. However, little research has examined such an effect on China’s public attitude to health issues. This article tries to fill the gap by examining how conventional factors linked to health behaviours – e.g. perceived threats, scientific knowledge, and trust in science—and ideological beliefs jointly influence the Chinese public’s attitude to the zero-COVID policies. Utilizing a national quota sample (n = 1,021) collected in April 2022 when Shanghai’s lockdown resulted in numerous online protests, this study found that perceived severity of COVID-19 infection, trust in science, left-leaning ideologies, and nationalism scores were associated with supporting the zero-COVID policies. Objective scientific judgments did not influence their views. Moreover, people whose ideological stances were closer to the official lines (political left and nationalism) were less likely to associate a zero-COVID attitude with perceived threats but more likely to link their trust in science to their support for the zero-COVID policy. The findings here provided empirical proof from China to the booming research agenda on the politicization of science and health communication while expanding our understanding of how ideological beliefs may have distorted scientific cognitions and health decisions.

Authors unavailable

Due to complex network threats, network security faces unprecedented challenges in a rapidly changing environment. These details highlight the importance of cryptography in protecting networks from today's threats. The development of technology has led to the increase in connected devices, the expansion of parking areas and the need for security measures. Honest and confidential information is protected by encryption technology using complex methods and algorithms. The brief reviews state-of-the-art cryptographic techniques and highlights the importance of quantum-resistant mechanisms against the threat of quantum computing. It explores how cryptography can be used together with technologies such as blockchain, artificial intelligence and the Internet of Things, and emphasizes its importance in ensuring the security of these areas. It envisions the development and implementation of post-quantum cryptography, covers concepts such as homomorphic encryption and zero-knowledge proofs, and addresses issues of cryptographic efficiency and creative control. It aims to protect networks from new threats and ensure secure data exchange by meeting the need for strong cryptographic protection in the evolving business environment.

Prof. Arpit Jain

Artificial Intelligence (AI) models are increasingly integrated into high-stakes domains such as finance, healthcare, autonomous systems, and legal decision-making. As their influence expands, concerns about accountability, fairness, transparency, and regulatory compliance have become central to both researchers and practitioners. One of the key challenges is auditing AI models in a manner that is tamper-proof, verifiable, and compliant with evolving regulatory frameworks. Traditional auditing mechanisms rely heavily on centralized logs and organizational trust, which creates vulnerabilities in terms of manipulation, incomplete records, and opacity in data flows. Blockchain technology—owing to its immutable, decentralized, and transparent nature—offers a powerful paradigm for establishing data provenance in AI auditing. By ensuring traceability of datasets, model updates, training logs, and inference outcomes, blockchain can provide regulators, stakeholders, and organizations with reliable audit trails. This paper presents a comprehensive exploration of blockchain-powered data provenance for AI model audits. It analyzes the limitations of current audit systems, evaluates how distributed ledger systems can strengthen accountability, and proposes an integrated framework that combines blockchain with cryptographic verification, zero-knowledge proofs, and federated logging to ensure verifiability without exposing sensitive data. The study synthesizes contributions from literature, presents a methodology for deploying blockchain-based provenance systems in AI pipelines, and evaluates potential results in terms of efficiency, compliance traceability, and security. Simulation experiments suggest that blockchain-enabled audits improve transparency, reduce fraudulent activities in AI operations, and enhance compliance readiness by more than 50% compared to traditional audit approaches.

Pawn, Rookie, Zhuan Cheng

NuLink provides privacy-preserving technology for decentralized applications via APIs. Users can securely store its valuable data, trade with others and so on. To ensure the privacy and security of service provided by NuLink, (zero-knowledge) proof systems are necessary. Zero-knowledge proof systems allow the prover to make the verifier believe that a certain conclusion is correct without providing any useful information to the verifier. In NuLink, we are going to use (zero-knowledge) proof system in the following three methods: 1. Users store their data through NuLink in a decentralized manner. To ensure that the storage clients are indeed storing the data, we employ proof of storage systems. In this system, users prepare certain challenges that can only be correctly answered by those who are actually storing the data. 2. Users have the option to outsource computations to NuLink. To verify the correctness of the computation results provided by the compute node, we require the node to provide a proof of correctness via SNARK systems. When sensitive parameters are used as inputs for computation, we utilize zk-SNARKs to prevent any potential leakage of these parameters. 3. Users may choose to trade their data through NuLink. To confirm that the buyer has sufficient digital funds and the seller possesses the desired data, both parties can provide a proof via zk-SNARKs. This builds confidence and prevents cheating during transactions. Using zero-knowledge proof systems, we can ensure that all nodes in NuLink behaves honestly and avoid cheating in the whole system.

Yuan Su, Yuheng Wang, Jiliang Li, Zhou Su · 6 authors

The Public Key Infrastructure (PKI) system is the cornerstone of today's security communications. All users in the service domain covered by the same PKI system are able to authenticate each other before exchanging messages. However, there is identity isolation in different domains, making the identity of users in different domains cannot be recognized by PKI systems in other domains. To achieve cross-domain authentication, the consortium blockchain system is leveraged in the existing schemes. Unfortunately, the consortium blockchain-based authentication schemes have the following challenges: high cost, privacy concerns, scalability and economic unsustainability. To solve these challenges, we propose a scalable and privacy-preserving cross-domain authentication scheme called Bifrost-Auth. Firstly, Bifrost-Auth is designed to use a decentralized oracle to directly interact with blockchains in different domains instead of maintaining a consortium blockchain and enables mutual authentication for users lying in different domains. Secondly, users can succinctly authenticate their membership of the domain by the accumulator technique, where the membership proof is turned into zero knowledge to protect users' privacy. Finally, Bifrost-Auth is proven to be secure against various attacks, and thorough experiments are carried out and demonstrate the security and efficiency of Bifrost-Auth.

Armando Cruz

Zero-knowledge proofs (zk-Proofs) are communication protocols by which a prover can demonstrate to a verifier that it possesses a solution to a given public problem without revealing the content of the solution. Arbitrary computations can be transformed into an interactive zk-Proof so anyone is convinced that it was executed correctly without knowing what was executed on, having huge implications for digital currency. Despite this, interactive proofs are not suited for blockchain applications but novel protocols such as zk-SNARKs have made zero-knowledge ledgers like Zcash possible. This project builds upon Wolfram's ZeroKnowledgeProofs paclet and implements a zk-SNARK compiler based on Pinocchio protocol.

Yongkai Fan, Binyuan Xu, Linlin Zhang, Gang Tan · 7 authors

Model prediction based on machine learning is provided as a service in cloud environments, but how to verify that the model prediction service is entirely conducted becomes a critical challenge. Although zero-knowledge proof techniques potentially solve the integrity verification problem when applied to the prediction integrity of massive privacy-preserving Convolutional Neural Networks (CNNs), the significant proof burden results in low practicality. In this research, we present psvCNN (parallel splitting zero-knowledge technique for integrity verification). The psvCNN scheme effectively improves the utilization of computational resources in CNN prediction integrity, proving by an independent splitting design. Through a convolutional kernel-based model splitting design and an underlying zero-knowledge succinct non-interactive knowledge argument, our psvCNN develops parallelizable zero-knowledge proof circuits for CNN prediction. Furthermore, psvCNN presents an updated Freivalds algorithm for a faster integrity verification process. Experiments show that psvCNN is practical and efficient in terms of proof time and storage, generating a prediction integrity proof with a proof size of 1.2MB in 7.65s for the structurally complicated CNN model VGG16. psvCNN is 3765 times faster than the latest zk-SNARK-based non-interactive method vCNN, and 12 times faster than the latest sumcheck-based interactive technique zkCNN in terms of proving time.

Smita Dhote, Priya Maidamwar, Shruti Thakur

The issuance of Tamper-Proof Certificates for Authentic Credentials is a cornerstone for establishing trust in various domains, including academia, government, and industry. Despite the pivotal role these certificates play, there is limited consensus on the most secure, cost-effective, and scalable models for their issuance. An empirical review of existing security models used for generating and distributing these critical assets. This study employs a multi-dimensional evaluation framework, focusing on four key metrics: security robustness, deployment cost, operational complexity, and scalability. The analysis not only encompasses traditional methods but also examines emerging technologies like blockchain and Zero-Knowledge Proofs. After a rigorous evaluation, there are strengths and weaknesses for each model, providing a comprehensive comparison. The findings reveal that while no single model excels in all metrics, certain approaches offer a more balanced trade-off among the evaluated criteria. In conclusion by offering well-grounded recommendations on which methods are superior when considering individual and combined metrics, thus providing invaluable insights for stakeholders in making informed decisions for implementing tamper-proof certificate issuance systems.

Fen Liu, Yongqiang Li, Huiqin Chen, Lin Jiao · 6 authors

With the growing practical applications of fully homomorphic encryption (FHE), secure multi-party computation (MPC), and zero-knowledge proofs (ZK), there has been an increasing need to design and analyze symmetric primitives that have low multiplication complexity and depth. In this paper, we propose a permutation constructed upon a 4-round nonlinear feedback resistor over$ \mathbb {F}_{q}^{4}$. Our proposed permutation has a multiplication depth of 2 and a multiplication complexity of 4. Significantly, its maximum differential/linear probability is bounded by$q^{-2}$. Based on this nonlinear function, we propose a new family of block ciphers over$ \mathbb {F}_{q}^{16}$called$ \mathsf {YuX}$, whose decryption circuit is highly efficient for FHE evaluation. We further provide specific instantiations, denoted as$ \mathsf {Yu_{2}X}$and$ \mathsf {Yu_{\mathrm {p}}X}$, wherein$q$takes the form of either$2^{n}$or a prime$p$, respectively. Furthermore, we conduct a comprehensive security analysis of$ \mathsf {YuX}$within certain parameters against various cryptanalysis methods employing automatic analysis tools, including the differential attack, linear attack, impossible differential attack, zero-correlation attack, and integral attack, as well as Gröbner basis and linearization attacks. Our research indicates that$ \mathsf {YuX}$maintains a robust security margin against those attacks. Finally, we present a detailed implementation of$ \mathsf {Yu_{2}X}$and$ \mathsf {Yu_{\mathrm {p}}X}$employing the BGV homomorphic encryption scheme. In comparison to ciphers over a field of characteristic 2, the outcomes evince that$ \mathsf {Yu_{2}X}$-8 (over$ \mathbb {F}_{2^{8}}^{16}$) and$ \mathsf {Yu_{2}X}$-16 (over$ \mathbb {F}_{2^{16}}^{16}$) achieve remarkably competitive throughputs, boasting performance approximately 12 times, 17 times, and 9 times superior to AES-128, CHAGHRI, and LowMC-128 (under 128-bit security), respectively. Furthermore, when juxtaposed with ciphers over a field of characteristic$p$, the outcomes affirm that the throughput of$ \mathsf {Yu_{\mathrm {p}}X}$-65537 (over$ \mathbb {F}_{65537}^{16}$) retains considerable competitiveness, registering an approximate fivefold enhancement relative to HERA. Evidently,$ \mathsf {YuX}$exhibits superior throughput compared to a majority of symmetric ciphers within this category.

Lu Zhou, Abebe Diro, Akanksha Saini, Shahriar Kaisar · 5 authors

Identity sharing systems, regardless of their architectural models, share common vulnerabilities. These systems compel users to divulge personal information and furnish proof of identity for accessing services, leaving them susceptible to data breaches that can culminate in identity theft and jeopardize online data security. While blockchain technology offers a potential remedy, delivering enhanced security, immutability, and traceability, it simultaneously raises pertinent concerns surrounding privacy and transparency. The integration of zero-knowledge proof (ZKP) technology has emerged as a promising solution, particularly in enhancing privacy within the transparent blockchain ecosystem. Our paper conducts an exhaustive survey of the existing literature, with a particular focus on the assimilation of ZKP technology into blockchain for the secure sharing of user identities. We undertake a critical evaluation of the advancements achieved in this domain, pinpoint the formidable challenges that must be confronted, and uncover nascent opportunities for further exploration. Our contribution transcends the realms of mere summarization and analysis; we go a step further by offering recommendations drawn from real-world case studies and delineating future research directions.

Martin Dietrich Brauch

Ambitious and comprehensive public policies are needed to drive and regulate climate investment by the public and private sectors. Policies are also needed to ensure a just transition, in line with human rights requirements and the sustainable development goals. As Brazil seeks to play a leadership role in the global race to net zero, and given the country’s unique emissions profile, what should its climate policy package look like?

Lisa Downing

In Materialism from Hobbes to Locke, Stewart Duncan provides a lucid and judicious investigation of some central episodes in the history of materialism in seventeenth-century Britain. The book begins with an examination of Thomas Hobbes’s defense of materialism. Duncan then considers three significant critics of Hobbes’s materialism: Henry More, Ralph Cudworth, and Margaret Cavendish. Last, he turns to a four-chapter treatment of issues surrounding materialism in John Locke. A brief epilogue considers Locke’s influence on Toland and Collins.In chapters 1 and 2, Duncan displays his expertise concerning Hobbes on language and ontology. Chapter 1 focuses on Hobbes contra Descartes in the Objections and Replies to the Meditations. This is a helpful context for understanding Hobbes’s materialism, as well as providing critical background for any discussion of ontology in the early modern period. In addition to the obvious topic of the nature of finite minds, a critical topic of disagreement is what we can and cannot have ideas of, and why. Here Duncan highlights the perhaps surprising connection drawn between imagism about ideas and materialism (vs. dualism) in the period. Chapter 2 digs into Hobbes’ defenses of materialism in the Elements of Law, De Corpore, and the Leviathan, critically evaluating both Hobbes’s arguments for materialism and his prospects for providing a materialist account of mind.In chapters 3 and 4, Duncan considers several less canonical figures who articulate important positions in the debate over materialism. Cudworth, More, and Cavendish all criticize Hobbes and find his materialist ontology lacking, while, further, agreeing that Descartes’s dualist and mechanist view is inadequate to explain the physical world. Of course, their positive views are quite different: Ralph Cudworth and Henry More endorse a dualism of immaterial spirits and material bodies, and they posit one (More’s spirit of nature) or many (Cudworth’s plastic natures) nonrational spirit(s) to order the physical world—whereas Margaret Cavendish endorses a vitalist or panpsychist materialism, one that posits three degrees of matter (inanimate, sensitive, and rational), with all three degrees intermingled in all actual matter. Duncan does a fine job introducing these figures and zeroing in on their relation to Hobbes’s materialism, though the reader may sometimes wish for more detail. (For example, what is animadversion? How is More’s critique of Hobbes on gravity supposed to work, and how does it relate to standard criticisms of Descartes on gravity?) Nevertheless, what Duncan does intriguingly investigate may prompt readers to pursue these topics further: for example, the different groundings of Cudworth and More’s arguments for the inadequacy of mechanism, the tensions in Cavendish’s views about a place for immaterial substances in her system.All this is a terrific context to bring to bear on Locke, whose Essay is strongly influenced by Hobbes throughout, as well as being even more obviously influenced by the strongest influence on Hobbes, namely, Descartes. And, by the standards of his time, Locke comes perilously close to endorsing the plausibility of Hobbesian materialism, while nevertheless doing his very best to critically distinguish himself from Hobbes.To consider Locke’s views about dualism versus materialism, one needs to consider his understanding of mind, of matter, and of their relation. On all three topics, Locke criticizes and rejects or revises Descartes. Or, as Duncan puts it, the version of dualism that Locke thinks might be true is not Descartes’s dualism. In chapter 5, Duncan provides an insightful tour of Locke’s anti-Cartesian responses to two questions: Is the idea of God innate? Is the soul always thinking? In considering the first question, he illuminates further the rather subtle connections between denying innate ideas and affirming materialism in the period. In considering the second, he clarifies the way in which Locke’s thinking thing is definitely not Descartes’s.In chapter 6, Duncan begins by considering the rather tortured question of Locke’s views about substance qua substratum, and our ideas thereof. Here Duncan argues, surprisingly briefly and quite persuasively, that Locke is addressing a psychological question of how we think about substance, and he gives a “bare substratum” account of that. While there is surely more to say about the extent to which some of Locke’s claims have metaphysical implications, Duncan’s core contentions here seem correct and exceedingly helpful. Duncan proceeds to demonstrate how useful it is to consider Locke’s discussion of substance in 2.23 in the light of Henry More, and, further, Duncan shows that there are strong indications that Locke was influenced by More’s The Immortality of the Soul. One upshot is the observation that both More and Locke are interested in rejecting Hobbes’s view that the notion of spirit as incorporeal substance is incoherent and unusable. More remarkable, though, is the way Duncan uses More to counter prominent interpretive claims1 that Locke is not considering a bare substratum view, and moreover, that such a view was not one that Locke’s relevant near predecessors or contemporaries would have taken seriously. Here Duncan argues that More is relevant context and that More seems to clearly articulate a bare substratum notion of substance. This is a very effective argument, and one that should attract discussion. It is worth emphasizing here, perhaps even more than Duncan does, that Locke is giving us his account of the idea of substance as substratum, which does not commit him to positing any bare particulars, and is also compatible with the (arguably Lockean) thought that this is a problematic idea that we use for want of a better. Last, Duncan sets up the next chapter by examining Locke’s 2.23 account of how we construct an idea of God.In chapter 7, Duncan adroitly defends a consistent and integrated set of positions on highly debated territory via a succinct discussion of 4.10, Locke’s defense of our knowledge of God’s existence. As part of this account, Locke argues that God must be immaterial. Many commentators (myself included) have thought that Locke’s argumentation here is in interesting tension with his position that human minds might, for all we know, be material; for in 4.10, Locke seems to raise deep objections to supposing that mere matter could ever think. Duncan discusses the full proof but attends most closely to the sections that argue, first, that the eternal being and first cause must be a cogitative being and, second, that that cogitative being cannot be material. Duncan warns us that Locke should not, by his own standards, be relying on an assumption that inconceivability implies impossibility, and he suggests that what is doing the real argumentative work is a principle of perfection: the more perfect cannot be caused by the less perfect.2 The principle of perfection, which Duncan shows can be traced to Cudworth, straightforwardly explains 4.10.10: an incogitative being cannot produce a cogitative one. For the principle to justify 4.10.16, Duncan seems to imply, Locke would have to be eliding a possible distinction between efficient causation and a synchronic grounding relation. (It appears that a criticism of Locke is implicit here, which one might wish had been made explicitly.). But if the principle of perfection implies that matter can never produce thought, this seems to require a strong reading of the “superaddition” in Locke’s famous remark that God might “superadd” thought to matter. That is to say, Duncan holds that the tension must be resolved by interpreting Locke as holding that if matter thinks, God must be the cause of that thought, in keeping with the principle of perfection. Here Duncan makes an extremely helpful distinction between “voluntarist” and “naturalist” interpretations of superaddition, based on whether or not thought is supposed to flow from the essence of body. Duncan nicely points out that the naturalist has a problem accommodating the principle of perfection. He argues that this rules out mechanist naturalism and complicates the prospects for a not-merely-mechanist naturalism (such as my own; see Downing 2007).3 The chapter is a genuine tour de force, in that along with defending a particular account of how the arguments of 4.10 are supposed to work, Duncan argues effectively for a particular account of what kind of materialism about human beings Locke thought might (for all we know) be true.Chapter 8 takes up another question about Locke’s relation to materialism: Did he think dualism or materialism more likely, or should we see him as neutral, affirming only that we cannot rule out either position with certainty? Duncan argues cogently for the neutral interpretation, despite the fact that Locke claims at one point that dualism is more probable, and despite the fact that many interpreters from Locke’s time on have seen Locke as unofficially inclined toward materialism.4 Interestingly, Duncan concludes by emphasizing how much Locke does in the Essay by way of defending philosophical views about the mind that are consistent with materialism and indeed make manifest its possibility.From the point of view of Locke scholarship, the book as a whole does a terrific job of succinctly supplying an illuminating context for considering Locke’s connections to materialism and, via judicious distinctions and arguments, motivating a specific and original set of interpretive claims. More broadly, it is a book that carefully investigates some varieties of materialism and responses to it in seventeenth-century Britain, while also indicating the rich tangle of issues connected to materialism (physical, metaphysical, epistemological, and religious issues, among others) that propelled arguments for and against. It’s a book that anyone interested in Locke or early modern materialism will want to read.

Bob Price, Bev Maleeff

Dear colleagues, we have a Cressington 108 carbon coater that uses carbon rods. After shaping the rods, I use sandpaper to make a flat surface and I wipe the powder away from the surface with a cloth. We use the maximal distance, approximately 10 cm, 4 volts and 10 seconds (we repeat 6-8 times with 1 minute pause in-between). Sometimes, there are sparks coming from the shaped rod and I don't know what I can do to avoid them. Quite frankly, this doesn't seem to affect the quality of the coating but still I wonder (1) why they appear (2) how they can affect my sample and (3) how to avoid them. Any thoughts? Stephane Nizet [email protected] If you have a shutter and the sparks are coming in the beginning or at a specific time: use it. Maybe a longer burn time and a shutter will do the trick. Stefan Diller [email protected] I suspect that it has something to do with the structure of the rod and the bonds between particles. I have come to expect them and to live with them. As you say, they don't seem to affect the bulk of the coating. I do try to limit the number of sparks. I control the current/voltage to allow a few per second. If there are none, it seems that the coating rate is very low. If the rate gets too high, the rod often fails too quickly. Warren Straszheim [email protected] You can try rinsing the rod with EtOH and then air gas blow-drying before use. Also, you can try a light burn (rod fire-red) for a few seconds before increasing the current. I don't believe the sparks will ruin your coating. Mike Delannoy [email protected] The sparks are basically glowing chunks of carbon coming from the arc. My experience is that the higher the current the more chunks are present. Generally, the chunks don't significantly affect the final product. So, like Mike Delannoy, I would set the current so occasional “sparks” are present as the optimum for deposition. You don't want a spray of sparks like a fireworks sparkler. Henk Colijn [email protected] I usually find it is because there is loose carbon on the tip. We use a folded paper towel. When the end of the flat carbon is scraped across an emory paper to remove embers from the last coating, it is always wiped on the paper towel. If we use a rod we have sharpened to a point, again we wipe off any loose carbon on the paper towel. Elaine Humphrey [email protected] You may need to shape the carbon rod with a carbon rod shaper for sharpening the 6.5 mm carbon rods into 3.5/3 mm cylindrical tips and 1.75/1.50 mm (3 diameters). It is important that the carbon rod has a reduced diameter at the tip. It is best to increase the voltage to 0.5 V. Abdelyamine Naitbouda [email protected] Dear EM Experts, some of my crystallographer colleagues and I wonder about the fundamentally different appearance of density histograms in EM Coulomb potential maps versus X-ray electron density maps. Here is the question: What I've noticed is that they are on different scales. That is understandable, as e/A3 is different than V. But there are papers showing that these values are somewhat proportional to each other for lower resolutions. But the other thing that I have noticed is that electron density maps have close to normally distributed value distributions, whereas cryoEM maps have a sharp spike and a very long tail. As a result, an electron density blob in an X-ray map looks nice somewhere around 3 sigma, whereas for cryoEM it's sometimes 10 sigma, 17 sigma, 20 sigma, all over the place. I'm thinking of using thresholds based on percentiles rather than sigmas, but my main question is: shouldn't the values on cryoEM maps also be approximately normally distributed? What is the cause of this non-normality? Sharpening? The raw experimental data themselves? Here is a potential partial answer: In cryo-EM, there is no absolute scaling, which means that density values can vary significantly. This variability can explain why different sigma values are consistently encountered. I can confirm that the density value distribution behaves as described, and I have also observed this. However, I cannot provide a definitive answer as to why this occurs. My best guess is that it may be related to B factor weighting in motion correction, but I cannot provide a conclusive explanation. What are we missing here? Ben Rupp [email protected] According to PDB/EMDB validation reports, this spike in the voxel value histogram is caused by masking. One validation report I have says: “A spike in this graph at zero usually indicates that the volume has been masked”. You can probably also find this note in validation reports of released PDB/EMDB entries. Opening a map from 3D refinement and one of the two half-maps from the same job seems to confirm this. The map’s histogram shows this spike at zero, but the half-map’s histogram doesn’t. Half-maps are never filtered nor masked, whereas the main map is masked (in cryoSPARC this is done by default, unless one turns off automatic masking and doesn’t provide any mask). The fact that there is no absolute scale for contour level in cryoEM maps is indeed annoying (I would like to compare maps without worrying that maybe I chose inadequate contour levels). My understanding is that it is caused at least in part by the fact that the size of the box enclosing the particle is arbitrary. Different amounts of low-value voxels between different maps give them different voxel value histograms, therefore choosing a contour level in terms of a certain number of standard deviations above the mean produces different results with different maps. Electron density maps from crystallography don’t have this variability because the box always spans a full unit cell, without this variable padding around the region of high density. At least this is how I understand Tom Goddard’s explanation in this discussion from last month on the Chimerax-users list. Maybe there are other reasons adding to this. I hope this helps. Guillaume Gaullier [email protected] Unfortunately, a fundamental mistake has been made in the much-cited paper by Erickson and Klug (1971) [https://doi.org/10.1098/rstb.1971.0040] more than 50 years ago. They assumed that the EM amplitude contrast of the (stained) biological object is proportional to the phase contrast of the same object over all spatial frequencies. If that were indeed the case, one single transfer function would suffice to describe how the linear imaging device would generate an output image. In reality, the amplitude contrast and phase contrast are two separate properties of the complex transmission function of the object, and these are associated with different physical properties [HA Ferwerda and MG van Heel (1978) https://doi.org/10.1007/978-1-4757-0665-9_47]. The problem is that the proportionality error has crept into almost all popular CTF determination programs where, say, 10% or 15% amplitude contrast is suggested ab initio. Any percentage of amplitude contrast erroneously causes the average density of the cryo-EM 3D reconstruction to deviate from zero. Any phase-contrast image must yield a zero average as it should be for any phase contrast image where what is measured is the difference in phase between any point in the back focal plane of the system with respect to the phase at the origin! That means that the phase at the origin must be zero. (Zero being the average density over the image around which the phase information is a to the transfer function will the of the CTF and the values in programs longer the That results no longer to each other and will also any with density maps in X-ray more Heel [email protected] I would be so with that paper from is always a certain level of experimental and as as I understand it at that time and level it as amplitude and phase be As you point this is the case, and I may a we years into the CTF for an filtered Here a CTF to and the in the experimental and CTF an contrast contrast by the is I for the quality of the but it the best we to with that very at that I may a of to all too that uses this at present. 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Rubana A.Khan, Bhavna Sharma, Nita M.Thakare

Due to exponential demand in IoT based healthcare, the demand for robust mechanisms to ensure data privacy, security, and scalability with the increasing dependence on cloud-based healthcare systems is immensely felt. Current approaches to dealing with health-care data in cloud settings lack the potency to tackle challenges emanating from the distribution of non-IID data, dynamic access control requirements, and secure cross-chain data analysis. These methods could not provide a holistic solution to adapt with the heterogeneous nature of healthcare data while maintaining advanced privacy and security levels over the distributed networks. In this way, the present work proposes to offer a secure and scalable protocol that is based on the blockchain for healthcare cloud data samples. It integrates the following four new methodologies: Adaptive Federated Learning for Healthcare Data, Secure Homomorphic Blockchain Encryption, Dynamic Attribute-Based Encryption for Healthcare, and Proof of Healthcare Privacy (PoHP) consensus based cross-chain federated Analytics with Zero Knowledge Protocol (ZKP) for healthcare. AFL-HD would work with optimal model training over the distributed healthcare data and thereby handle the challenges that are non-IID in nature, while reducing the communication overhead by 30-40%. SHBE would ensure a 1.5x improvement in encryption and decryption times and also enable secure computations on encrypted data samples. Thus, DABE-HC enables dynamic access control policy management in blockchains, while ensuring access control precision in excess of 99%, with near-instant policy updating. CCFA-HC supports X-blockchain privacy-preserving analytics, thereby reducing the cross-chain communication overhead by 20-30%. In this protocol, therefore, cloud healthcare data management is made more scalable, secure, and private. It allows tackling challenges in the healthcare domain and gives a holistic solution supporting meaningful and secure, efficient, and collaborative healthcare data processing and analytics across distributed environments. The impact of this work is immense in providing a foundation for the next generation of secure healthcare data systems.

Martin Pastyřík

Zero-knowledge SNARKs have become an extremely studied topic in cryptography due to their recent applications in modern cryptocurrencies. Most of these protocols are created using Polynomial Commitment Schemes such as the KZG protocol by Kate, Zaverucha, and Goldberg (ASIACRYPT 2010). Until recently, the known proofs of ex- tractability of the KZG protocol were either in idealized models or under very strong assumptions. This year, Lipmaa, Parisella, and Siim (EUROCRYPT 2024) proved the KZG protocol to be Special Sound and Black-Box Extractable in the standard model under their new ARSDH assumption. In this thesis, we build upon the work of Lipmaa et al. to prove Special Soundness for the bivariate version of the KZG polynomial commitment. To this end, we generalise their ARSDH assumption and define Special Soundness for the Bivariate KZG polynomial commitment. We then prove that the Bivariate KZG polynomial commitment achieves the Special Soundness under the ARSDH assumption and our generalisation of the AR- SDH assumption. Finally, we give a more refined analysis of the running time of the black-box extractor from Lipmaa et al. 1

Dennis Hofheinz, Kristina Hostáková, Roman Langrehr, Bogdan Ursu

No abstract is available for this record.