Blockchain Papers

Kazuo Takaragi, Takashi Kubota, Sven Wohlgemuth, Katsuyuki Umezawa · 5 authors

Central bank digital currencies require the implementation of eKYC to verify whether a trading customer is eligible online. When an organization issues an ID proof of a customer for eKYC, that proof is usually achieved in practice by a hierarchy of issuers. However, the customer wants to disclose only part of the issuer's chain and documents to the trading partner due to privacy concerns. In this research, delegatable anonymous credential (DAC) and zero-knowledge range proof (ZKRP) allow customers to arbitrarily change parts of the delegation chain and message body to range proofs expressed in inequalities. That way, customers can protect the privacy they need with their own control. Zero-knowledge proof is applied to prove the inequality between two time stamps by the time stamp server (signature presentation, public key revocation, or non-revocation) without disclosing the signature content and stamped time. It makes it possible to prove that the registration information of the national ID card is valid or invalid while keeping the user's personal information anonymous. This research aims to contribute to the realization of a sustainable financial system based on self-sovereign identity management with privacy-enhanced PKI.

R. Staufenbiel, Ruth Schmitt, A E Müller, Lydia Staufenbiel

INTRODUCTION: Undersupply and oversupply of dairy cows with essential trace elements should be avoided from the point of view of animal health and environmental pollution. The aim of the study was to proof the results faecal analyzes on the nutritional supply situation with essential trace elements in comparison to measurements from total mixed ration (TMR) analyses. Concentrations of iron (Fe), copper (Cu), zinc (Zn), Mangan (Mn), selenium (Se), cobalt (Co), molybdenum (Mo) were measured as representative multicentric random sample in 574 TMR, 600 pooled faecal and blood samples from dairy cows. Trace elements, Fe in 0 %, Se 18 %, Zn 43 %, Cu 52 %, Co 53 % and Mn 59 %, were within the target range. Undersupply was found in 0 to 8 % and an oversupply in 39 to 100 % of the TMR samples. The tolerance limit for Fe was exceeded in 11 % and for Mo in 13 %. The results indicate the need for optimized ration design. The trace element concentrations in the faecal samples varied over a wide range. Results of pooled faecal samples (n=10 per pool) corresponded closely with the mean values calculated from the individual samples (r2 > 0,9). Correlation between element concentrations in the TMR and faecal samples for Fe (r=0,687), Cu (r=0,675), Zn (r=0,635), Mn (r=0,656), Se (r=0,573), Co (r=0,795), and Mo (r=0,708) were highly significant. No correlations were detected between the element concentrations in the TMR and in the blood samples. The regression analyzes showed a highly significant linear adjustment of the measured value distribution around the regression lines over the entire value range including the zero point. Reference values were calculated for the faecal concentrations of Cu, Zn, Mn, Se and Co. Tolerance reference limits in the TMR were calculated for the faecal concentrations of Fe and Mo. The trace element concentrations in the TMR samples reflect the nutritional supply situation. Knowledge of the nutritional supply situation of the herd is of great importance for the stock management of dairy cow. Fecal sample analyzes can be used as an alternative to TMR examinations to assess the nutritional supply situation.

Shashank Joshi, Arhan Choudhury

A knowledge market can be described as a type of market where there is a consistent supply of data to satisfy the demand for information and is responsible for the mapping of potential problem solvers with the entities which need these solutions. It is possible to define them as value-exchange systems in which the dynamic features of the creation and exchange of intellectual assets serve as the fundamental drivers of the frequency, nature, and outcomes of interactions among various stakeholders. Furthermore, the provision of financial backing for research is an essential component in the process of developing a knowledge market that is capable of enduring over time, and it is also an essential driver of the progression of scientific investigation. This paper underlines flaws associated with the conventional knowledge-based market, including but not limited to excessive financing concentration, ineffective information exchange, a lack of security, mapping of entities, etc. The authors present a decentralized framework for the knowledge marketplace incorporating technologies such as blockchain, active inference, zero-knowledge proof, etc. The proposed decentralized framework provides not only an efficient mapping mechanism to map entities in the marketplace but also a more secure and controlled way to share knowledge and services among various stakeholders.

Dr. Muhammad Zain Abbas

As the digital ecosystem evolves, secure and efficient Digital IdentityManagement Systems (DIMS) have become pivotal in managing identities acrossgovernmental, financial, healthcare, and commercial sectors. This paper offers across-sectoral examination of DIMS, emphasizing security and privacy concerns andtheir mitigation strategies. Drawing on current technologies such as blockchain,biometrics, and zero-knowledge proofs, the study explores how these systems canprotect sensitive information while ensuring interoperability and compliance withregulatory frameworks. Through comparative analysis, graphical insights, and realworld case studies, the paper underscores the need for standardized and resilientidentity infrastructures that balance user privacy and system functionality

Kirk Curnutt

Scott Donaldson, writes James L. W. West III in his short but precise preface to Fitzgerald and the War Between the Sexes, a posthumous collection of essays by the late literary biographer (1928–2020) who was a mainstay of Fitzgerald studies for a half-century, “was an excellent scholar and a good man, generous with his time and knowledge. . . . He brought a newspaperman’s curiosity to his work and an open, accessible style to his writing” (West, “Preface” viii). From the beginning of his career, the prolific Donaldson was also a master of repurposing his wide-ranging contributions to American literary history and its development. Whereas most scholars are content to see an essay or chapter into print in one venue and move on, the author, perhaps most notably of The Impossible Craft: Literary Biography (2015), found inventive ways of repackaging and reconfiguring entries on his vita, sometimes decades after the fact. Twenty years ago, just before the dawn of the e-reader era, such long-out-of-print early efforts as his The Suburban Myth (1968) and Poet in America: Winfield Townley Scott (1972) reappeared under the aegis of the print-on-demand publisher iUniverse, making available in affordable softcover editions valuable studies that remained sequestered in university stacks, unavailable to most readers. This foray into self-(re)publishing soon led to a valuable relationship with Open Road Media, which produced digital versions of his controversy-scarred John Cheever: A Biography (1988) and the unjustly overlooked Archibald MacLeish: An American Life (1992).1 Thanks to the encouragement of the Minnesota Historical Society, the University of Minnesota Press also brought his much-admired Fitzgerald biography, Fool for Love: F. Scott Fitzgerald (1983), back to life for a new generation of scholars and fans.Perhaps most impressively, Donaldson himself rewrote nearly two dozen previously published journal articles to create the essential collection Fitzgerald and Hemingway: Works and Days (2009). It is hard to think of another omnibus of a commentator’s lifework whose contents fit together so seamlessly. By updating each essay’s secondary sources and revising for overall unity and cohesion of voice, Donaldson pulled off the rare feat of compiling a “greatest hits” collection that never sounds dated, whose analyses feel fresh and insightful rather than like time capsules from, say, 1973 (when the well-known essay “Scott Fitzgerald’s Romance with the South” first appeared in the Southern Literary Journal) or 1982 (when the oft-republished “Money and Marriage in Fitzgerald’s Stories” was featured in Jackson R. Bryer’s collection The Short Stories of F. Scott Fitzgerald: New Approaches in Criticism).Fitzgerald and the War Between the Sexes is not, as its title may imply, a focused dissection of a specific theme across an array of Fitzgerald efforts. Rather, it is a gathering of five late efforts either unpublished or uncollected at the time of their author’s death. One main selling point of the book is its compact size and affordability: at a brisk 132 pages and a $15.95 paperback list price, the collection represents an initiative on the part of West and Penn State University Press to produce critical studies of Fitzgerald for the general reader. (West’s own Business Is Good: F. Scott Fitzgerald, Professional Writer, coming in 2023, will be the second book in the series.) The centerpiece here is a sixty-three-page excursion into the gender dynamics of Tender Is the Night, “Tender Is the Night: The War Between the Sexes” (1–63), which West calls “the best close reading of the novel that I have seen” (“Preface” vii). I would agree with this assessment; its core appeal is its neutrality. Ever the journalist, Donaldson declines to take a position on the contentious gender politics in the novel that can make Fitzgerald seem at best an essentialist when it comes to sexual difference and at worst a misogynist in his insistence that modernity eroded the fundamental strengths of manhood.Another of the great pleasures that accounts for the essay’s readability is that Donaldson does not harp on his thesis. Rather, he lets his discussions of key moments in Fitzgerald’s fourth novel flow with a spontaneity that arises in part from his nonchronological analysis. His discussion begins in media res, focusing on the moment in book 2, chapter 14, when Dick Diver treats (not very effectively or with much sympathy) the eczemic “woman in room twenty.” As Donaldson argues, the patient’s inflamed skin is Fitzgerald’s most autobiographical nod to the torments suffered by his wife during the initial months of her protracted hospitalization at Dr. Oscar Forel’s Les Rives de Prangins Clinic in Nyon, Switzerland, a that the to the Dick that is the of the of time who to the and that Fitzgerald his and her in the her novel the and her to and in the that this is as and as the that in gender is Donaldson is the who the the Tender Is the the From the essay on the ways in which the of “the of to Dick Diver by The from the Diver and to a that and the wife and of who as a by a and whose with Fitzgerald’s the to his Donaldson for A on and essential and to Fitzgerald’s 2, chapter a that to on her in the the of Dick and as for the that to by to as the of a as which to Dick to Donaldson not in the have the of his as a for his her own to such as to I to as a from to a from to of the than the during their than a in American Donaldson as part of his the essay also the of which Dick and As Donaldson Fitzgerald’s of the of in the relationship and may have to the the of the of and in that Tender Is the be for in the of the and the of remained a rather for the was the of a a into a a Fitzgerald best his for in which he previously in his first two This of and The and As Donaldson argues, the for of whose for and and from the of which the the in to to and Literary the own in his of his of and the and his to for his from the can the novel and the of the to A on of his “the of his and his into the of politics by a New of of of of his in the in the dissection of the of or is in Donaldson calls the and that can have on of its like who may in the feel to by the of the perhaps the of to have than as the of by and the Diver and the to the for the that one that to the very that that the very as his was in a that Dick is in the the and are to the that into its It may be that the a and is to the but on from for “the of his and and are the main as in a A discussion of book chapter at the that the to an on the that of her in the As Donaldson on de a a at her de in the an their and and A and a after their de was a in a second when her the of was to at a and the of studies that the in the of the to Tender is not and de in their to the novel is not A second to the that a of R. a to in of the to the of the late the of and in Tender was from a also the and the during the two years in which the was to his of is the he that is Fitzgerald’s at than it his in he and in a for that one of this the Donaldson as to the is that Fitzgerald this Donaldson “the that was of it on to his The very on the to which the of and Fitzgerald’s as the essay that Tender Is the is a novel that does not have to take in an to the War Between the Sexes” is such a de that one can it the essays that can but its rather and the American is a of Fitzgerald’s most novel that its general as the at the and Literary in New in an when that was the for book in the the essay a and specific who may not have or to its and pleasures the it can as a American of the novel as “the first that American in Donaldson Fitzgerald to James as a who the and the for and the As he and to the than most who are off by her and that his Donaldson together a of and and an of and is his discussion of as to is for the of As he are at and like the in a that the of the of is the one with which are This of of the the of a literary and her previously appeared as a core chapter in The Impossible that that on literary for for an after nearly years it was first I West to it to make it This is a good for the key of and is a master in the and that into literary From The of Fitzgerald: An American Life Donaldson have and to their of as the of the with was The to the essay is the that the to into his of The and the that an American the of found in is and Scott Fitzgerald, A Marriage by with the and her in of is so in its of that one scholars would its on such say, Fitzgerald’s with Fitzgerald is a of the in the not just his but efforts such as and his The appeared in the of The Fitzgerald in and as the for not one but two in Works and and of The The have from one a into the that is a . . . that articles have published that will be in a book by James L. 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Makhmoor Bashir, Abdulaziz Alfalih, Sudeepta Pradhan

No abstract is available for this record.

Alex Lombardi, Fermi Ma, Nicholas Spooner

When do classical zero-knowledge protocols remain secure against quantum attacks? In this work, we develop the techniques, tools, and abstractions necessary to answer this question for foundational protocols:1)We prove that the Goldreich-Micali-Wigderson protocol for graph non-isomorphism and the Feige-Shamir protocol for NP remain zero-knowledge against quantum adversaries. At the heart of our proof is a new quantum rewinding technique that enables extracting information from multiple invocations of a quantum adversary without disturbing its state.2)We prove that the Goldreich-Kahan protocol for NP is post-quantum zero knowledge using a simulator that can be seen as a natural quantum extension of the classical simulator.Our results achieve negligible simulation error, appearing to contradict a recent impossibility result due to Chia-Chung-Liu-Yamakawa (FOCS 2021). This brings us to our final contribution:3.We introduce coherent-runtime expected quantum polynomial time, a simulation notion that (a) precisely captures all of our zero-knowledge simulators, (b) cannot break any polynomial hardness assumptions, (c) implies strict polynomial-time ε-simulation and (d) is not subject to the CCLY impossibility. In light of our positive results and the CCLY negative results, we propose coherent-runtime simulation to be the appropriate quantum analogue of classical expected polynomial-time simulation.

Huancheng Lin, Zhehan Wang, Tong Xu, Shanyue Zhou · 6 authors

Recently passwordless authentication such as zero-key authentication or zero-knowledge access control is becoming popular among businesses prioritizing their users' and employees' security and digital experience. A challenge-response mechanism and public key infrastructure (PKI) cryptography are employed to perform the zero-key authentication or zero- knowledge access control that authorizes user access to an online service without a password or any shared secret required. Using a large quantum computer, a quantum algorithm could break the hard mathematical problems underlying PKI. The National Institute of Standards and Technology (NIST) has launched a program and competition to standardize one or more post-quantum cryptographic (PQC) algorithms to fight against quantum attacks. In this paper, we have conducted the first-ever mathematical analysis of lattice-based and polynomial-based PQC by introducing the relationship between automorphism and homomorphism. This analysis can help enterprises and organizations leverage NIST-selected PQC algorithms to safeguard their online services from quantum attacks. We performed the simulation to illustrate brute force broken probability for polynomial-based or multivariate-based PQC to validate our mathematical analysis of PQC.

Chao Wang, Zhongyuan Yao, Yong Zhang, Shangkun Guo · 6 authors

Blockchain technology is currently a research hotspot in the computer field. However, with the rapid development of blockchain technology, poor storage scalability limits its further application. In response to this problem, this paper proposes a multi-chain storage scheme based on hash calendar and recursive zero-knowledge proof, which consists of two parts: off-chain and on-chain. The off-chain part uses hash calendar technology to store account information, and through recursive zero-knowledge proof of account state transitions, ensures the verifiability of off-chain state transitions and improves the security of the solution; and sets up proof generators and transactions The two roles of the executor improve the efficiency of transaction execution. A dynamically addable main and sub-chain array is designed on the chain. The sub-chains store the brief information of transactions and the world state. The main chain is responsible for verifying the correctness of off-chain state transitions. On-chain and off-chain collaborative storage reduces the space occupied by data., to realize the storage expansion of the blockchain. Finally, simulation experiments show that this scheme can effectively realize the storage expansion of blockchain.

Junbeom Park, Seongju Chang

The Internet of Things (IoT) and blockchain technologies characterizing the era of the fourth industrial revolution have enabled smart home networks to support their various systems and services. In a blockchain-based smart-home network environment, all connected IoT devices must be controlled safely and efficiently. Nevertheless, existing block-chain-based smart-home IoT systems pose a delay issue due to the necessary block generation time. In addition, IoT devices installed in smart homes should be able to prevent forgery attacks such as spoofing because they are often directly associated with personal information. In this study, we proposed an enhanced method to control smart home devices safely and efficiently by applying the zero-knowledge proof combined with a blockchain-based IoT system to protect the public keys of home network devices and the communication among them. The proposed model was approximately 10 s faster than the block generation-based model when it communicated three times in rinkeby, which is one of the test networks of Ethereum.

Nikos Fotiou, Vasilis Kalos, Yannis Thomas, George Xylomenos · 6 authors

Information-Centric Networking (ICN) is a Next Generation Internet architecture that facilitates content sharing. ICN natively supports content multi-sourcing, allowing content items to be stored in multiple storage nodes. In order to ensure data integrity, data owners can sign their content items. This, however, prevents storage nodes from sharing partial content items. We present a data sharing scheme where data owners store structured data items (e.g., IoT measurements) in semi-trusted storage nodes. We allow data consumers to express interest for a portion of a data item and we enable storage nodes to “hide” the remaining item without invalidating its integrity. We achieve our goal by leveraging BBS+ digital signatures that support selective data disclosure through Zero-Knowledge Proofs. We define a protocol for data owners to issue authorizations in the form of Verifiable Credentials, which indicate which parts of the data a consumer is allowed to access, and a protocol for consumers to send these authorizations inside ICN Interests. This allows storage nodes to implement fine grain access control, without having access to the secrets of the data owners, while data consumers can still verify the authenticity and integrity of the partially revealed data. In addition to its security advantages, our solution requires significantly less storage and communication overhead compared to an approach that relies on commonly used digital signature algorithms.

Qiwei Hu, Yueyue Dai, Shuo Li, Tao Jiang

Blockchain-enabled IoT Access Control (BIAC) is a promising paradigm to achieve reliable and automatic access control management for IoT systems. Due to the involvement of blockchain which is transparent, account privacy is easily violated in BIAC. Motivated by the recent progress of utilizing Zero Knowledge Proof (ZKP) to protect account privacy in cryptocurrencies, this article systematically investigates a ZKPbased privacy-enhancing BIAC architecture. We summarize the design principles as authenticating transactions with ZKP proofs instead of digital signatures so that permissions are linked to off-chain secrets rather than on-chain accounts. However, since the ZKP proofs are stored on the blockchain, an adversary may launch replay attacks to access resources illegally. To tackle this challenge, we carefully design two account-hiding transactions as well as validation rules for the classical capability-based AC (CBAC) model, where all ZKP proofs expire once used. The enhanced system preserves all necessary functions of CBAC while achieving permission invisibility and requester anonymity. We implement the designed ZKP operations, where the evaluation results demonstrate our solution incurs low overheads.

Peifang Ni

Zero-Knowledge Contingent Payment presents how Bitcoin contracts can provide a solution for the so-called fair exchange problem.Banasik, W. et al. first presented an efficient ZeroKnowledge Contingent Payment protocol for a large class of NP-relations, which is a protocol for selling witness. It obtains fairness in the following sense: if the seller aborts the protocol without broadcasting the final message then the buyer finally gets his payment back. However, we find that the seller in the protocol could refuse to broadcast the final signature of the transaction without any compensation for the buyer. As a result, the buyer cannot get the witness from the final signature of the transaction and has the payment for the witness locked until finishing the large computation for a secret signing key. In this paper, we fix this problem by augmenting the efficient Zero-Knowledge Contingent Payment protocol. We present a new protocol where the seller needs to provide the deposit before the zero-knowledge proof of knowledge of the witness being sold. And then the buyer could obtain the seller's witness if the seller broadcasts the final signature of the transaction and gets the payment and his deposit. Otherwise, the buyer could get back the payment and obtain the seller's deposit. This new augmented protocol is constructed without any new assumptions.

Peizheng Yan, Kaixi Wang, Xiaozhu Jia

In the distributed environment, when all parties carry out the cooperative computing, there are problems of low scalability and privacy leakage. To solve the above problems, this paper proposes a scheme that integrates the secret sharing and distributed steganography. Arnold transform is performed to encrypt the secret before the communication, and this transform can effectively improve the robustness of secret transmission. After a secret is embedded in a cover, the scheme uses random numbers to generate multiple sub-stego-objects, then carries out the distributed storage and communication for these sub-stego-objects. The identity of the sender is verified by the receiver using Schnorr zero-knowledge proof at the local, which reduced interaction between the sender and the receiver, and no more information is not obtained by the receiver except the stego-object. As a result, the receiver does not communicate directly with the sender, which, to some extent, can avoid the attention of the steganography from external attackers. Additionally, this scheme can still work even in the case that some users were disconnected from the system after a stego-object is transmitted. After analyzing how the scheme supports more senders, the correctness of the scheme is also proved in detail.

Shuhao Zheng, Yanxi Lin, Yang Yu, Ye Yuan · 6 authors

Auditing the information leakage of latent sensitive features during the transborder data flow has attracted sufficient attention from global digital regulators. However, there is missing a technical approach for the audit practice due to two technical challenges. Firstly, there is a lack of theory and tools for measuring the information of sensitive latent features in a dataset. Secondly, the transborder data flow involves multi-stakeholders with diverse interests, which means the audit must be trustless. Despite the tremendous efforts in protecting data privacy, an important issue that has long been neglected is that the transmitted data in data flows can leak other regulated information that is not explicitly contained in the data, leading to unaware information leakage risks. To unveil such risks trustfully before the actual data transfer, we propose FIAT, a Fine-grained Information Audit system for Trustless transborder data flow. In FIAT, we use a learning approach to quantify the amount of information leakage, while the technologies of zero-knowledge proof and smart contracts are applied to provide trustworthy and privacy-preserving auditing results. Experiments show that large information leakage can boost the predictability of uninvolved information using simple machine-learning models, revealing the importance of information auditing. Further performance benchmarking also validates the efficiency and scalability of the FIAT auditing system.

Anais Querol Cruz

Internet fue concebido hace décadas como un protocolo de intercambio de información telemáticamente a través de redes de máquinas interconectadas. Pero hace tiempo que sufre de problemas estructurales como la centralización de servicios y el alto nivel de confianza que se debe depositar en los servidores; perpetuando cuellos de botella y ciberataques. En este escenario nació blockchain, una tecnología descentralizada y transparente que ha llegado para mejorar la web que conocemos. Las cadenas de bloques, son listas de registros enlazados entre sí, securizados utilizando métodos criptográficos y repartidos a lo largo de los nodos de la red. Su utilidad principal es la de almacenar información de una forma verificable e inmutable; es decir, que un usuario pueda comprobar la integridad de los datos de las mismas. Si bien parece que la transparencia no puede conjugarse con la naturaleza de los datos más sensibles, la criptografía moderna ofrece herramientas como las pruebas de conocimiento cero (ZKPs), que permiten armonizar privacidad y transparencia. Eso es, verificar propiedades de la blockchain sin filtrar información privada. Además, otros mecanismos como los argumentos sucintos (SNARKs), permiten comprobarlo de forma eficiente sin perder seguridad. Junto con metodologías basadas en compromisos criptográficos (CP), es posible combinar estos métodos para construir sistemas para demostrar afirmaciones cada vez más complejas. El objetivo de mi tesis es mejorar estos métodos para que se puedan aplicar a casos de uso realistas. Para ello, propongo unos bloques modulares que respetan la privacidad y se combinan entre sí de forma fácil y segura con un compilador para que los desarrolladores puedan crear blockchains transparentes y descentralizadas con todas las garantías de privacidad y seguridad de forma eficiente. Para ello, propongo una serie de CP-SNARKs eficientes para verificar propiedades frecuentes a la hora de diseñar estos sistemas, como lo son multiplicaciones matriciales, relaciones lineales, chequeo de sumas o autopermutaciones. Estos módulos se pueden interconectar para construir argumentos más complejos. Gracias a nuestro compilador podemos reutilizar SNARKs con conocimiento cero (zkSNARKs) existentes. Combinando nuestros componentes, presentamos el primer zkSNARK universal con clave lineal. Por otra parte, diseñamos una familia de zkSNARKs universales, actualizables y lineales (y sus variantes CP-SNARKs) para un nuevo sistema de restricciones de propósito general llamado R1CS-lite más eficiente que R1CS. Nuestro mecanismo funciona en dos fases: la primera, pruebas para un objeto abstracto llamado PHPs; la segunda, compilación a zkSNARKs mediante CP-SNARKs modulares para tres relaciones principales—apertura de compromisos polinomiales, igualdad de ecuaciones, y grado de polinomios. Las distintas configuraciones derivan en las distintas variantes de nuestros esquemas. Por último, nos interesamos en el estudio de zkSNARKs en entornos distribuidos. Aquí, la prueba se genera de forma fragmentada por los distintos nodos y es agregada por un único coordinador, preservando la privacidad entre entidades. Mostramos un mecanismo para obtener PHPs bivariables, que se compilan a zkSNARKs paralelas. ----------ABSTRACT---------- The Internet was conceived decades ago as a protocol for the telematic interchange of information through networks of interconnected machines. But it has been some time since it suffers from some structural problems such as services centralization and the high level of trust to be deposited on servers; perpetuating bottlenecks and cyberattacks. In this scenario blockchain was born, a decentralized and transparent technology that has arrived to improve the web we all know. Blockchains, as their name suggests, are lists of linked registers, secured using cryptographic methods and disseminated across the nodes of the network. Their main utility is to store data in a verifiable and immutable way: meaning, that users can check the integrity of this information. Even if it looks like transparency cannot marry to the nature of sensitive data, modern cryptography offers tools such as zero-knowledge proofs (ZKPs), which can harmonize privacy and transparency. That is, verifying properties of the blockchain filtering no private information. Moreover, other mechanisms like succinct arguments (SNARKs), allow for checking them efficiently without detriment to security. Together with the commit-and-prove (CP) approach, these methods can be put together to build systems to prove even more complex claims. The goal of my thesis is to enhance these methods so that they can be applied to realistic use cases. To this effect, I propose some privacy-preserving modular blocks (CP-SNARKs) that can be combined with each other easily and in a secure way with a compiler, so as that developers can create transparent and decentralized blockchains with all guarantees of privacy and security in an efficient manner. With this goal in mind, I propose a series of efficient CP-SNARKs to verify frequent properties when designing these systems, such as matrix multiplications, linear relations, sum-checks, or self-permutations. These modules can be interconnected to build more complex arguments. Thanks to our compiler we can also reuse other existing zeroknowledge SNARKs (zkSNARKs). Combining our components, we present the first universal zkSNARK with linear length keys. On the other hand, we design a family of universal and updateable zkSNARKs with linear SRS (and their CP-SNARKs variants) for a new general-purpose constraint system called R1CS-lite which is more efficient than R1CS. Ours is a two-fold mechanism: first, proofs for an abstract object called PHPs; second, compiling to zkSNARKs through modular CP-SNARKs for three main relations—opening of polynomial commitments, equality of equations, and degree of polynomials. Distinct configurations derive from the different variants of our schemes. Lastly, we put our focus on the study of zkSNARKs in distributed environments. Here, the proof is generated in a fragmented way by the independent nodes and is aggregated by an only coordinator, preserving privacy among entities. We show a mechanism to obtain bivariate PHPs, which can be compiled to parallel zkSNARKs using our previous compiler.

Lijie Chen, Ramis Movassagh

Recently Chen and Movassagh proposed the quantum Merkle tree, which is a quantum analogue of the well-known classical Merkle tree. It gives a succinct verification protocol for quantum state commitment. Although they only proved security against semi-honest provers, they conjectured its general security. Using the proposed quantum Merkle tree, they gave a quantum analogue of Kilian's succinct argument for NP, which is based on probabilistically checkable proofs (PCPs). A nice feature of Kilian's argument is that it can be extended to a zero-knowledge succinct argument for NP, if the underlying PCP is zero-knowledge. Hence, a natural question is whether one can also make the quantum succinct argument by Chen and Movassagh zero-knowledge as well. This work makes progress on this problem. We generalize the recent result of Broadbent and Grilo to show that any local quantum verifier can be made simulable with a minor reduction in completeness and soundness. Roughly speaking, a local quantum verifier is simulable if in the yes case, the local views of the verifier can be computed without knowing the actual quantum proof; it can be seen as the quantum analogue of the classical zero-knowledge PCPs. Hence we conjecture that applying the proposed succinct quantum argument of Chen and Movassagh to a simulable local verifier is indeed zero-knowledge.

Amit Kumar Singh, Kamalesh Acharya, Ratna Dutta

No abstract is available for this record.

Yuling Chen, Junhong Tao, Tao Li, Jiangyuan Cai · 5 authors

Abstract Secure comparison protocol is an important branch of secure multi-party computation(SMPC), which compares the size of input data without disclosing any information between participants. The development of cloud computing provides an application platform for SMPC, but it also brings new challenges. In cloud computing with SMPC, clients need to process their own data and submit the processed data to a cloud server, which then performs the computation. In this process, not only the clients need to maintain an honest state at all times, but sensitive data on the cloud server side may also be exposed. In this paper, zero-knowledge proof and homomorphic encryption techniques are used to improve Damgård-Geisler-KrØigaard(DGK) comparison protocol. The improved secure comparison protocol can not only safely calculate private data, but also be applicable to malicious participant model. Finally, the security analysis shows that the proposed scheme not only ensures the privacy security of participants, but also ensures the data fairness of comparison protocols.

Chunjie Guo, Lin You, Gengran Hu

Biometric identification is a convenient and reliable method in identity authentication. The widespread adoption of biometric identification requires strong privacy protection against possible theft or loss of biometric data. Existing techniques for privacy-preserving biometric identification mainly rely on traditional cryptographic technology such as oblivious transfer and homomorphic encryption, which will incur huge expenses to the system and cannot be applied to large-scale practical applications. For these issues, we propose a biometric identification scheme by constructing zero-knowledge succinct noninteractive argument of knowledge (zk-SNARK). Our scheme not only reduces the communication overhead, which only needs to send 8 constants to the verifier but also can protect the fingerprint template from disclosure. The time complexity of proof generation and proof verification are about O(C) and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mi>O</a:mi> <a:mfenced open="(" close=")" separators="|"> <a:mrow> <a:mi>x</a:mi> </a:mrow> </a:mfenced> <a:mo>+</a:mo> <a:mi mathvariant="normal">log</a:mi> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>C</a:mi> </a:math> , respectively, and the size of the proof is only 8 constants, where C and x represent the size of the circuit and the public input, respectively. We have implemented the proposed authentication solution on a public data set of fingerprint images and evaluated the performance and security.

Wei Liu, Jian Weng, Bingsheng Zhang, Kai He · 5 authors

No abstract is available for this record.

Zvika Brakerski, Ran Canetti, Luowen Qian

In the classical model of computation, it is well established that one-way functions (OWF) are minimal for computational cryptography: They are essential for almost any cryptographic application that cannot be realized with respect to computationally unbounded adversaries. In the quantum setting, however, OWFs appear not to be essential (Kretschmer 2021; Ananth et al., Morimae and Yamakawa 2022), and the question of whether such a minimal primitive exists remains open. We consider EFI pairs - efficiently samplable, statistically far but computationally indistinguishable pairs of (mixed) quantum states. Building on the work of Yan (2022), which shows equivalence between EFI pairs and statistical commitment schemes, we show that EFI pairs are necessary for a large class of quantum-cryptographic applications. Specifically, we construct EFI pairs from minimalistic versions of commitments schemes, oblivious transfer, and general secure multiparty computation, as well as from QCZK proofs from essentially any non-trivial language. We also construct quantum computational zero knowledge (QCZK) proofs for all of QIP from any EFI pair. This suggests that, for much of quantum cryptography, EFI pairs play a similar role to that played by OWFs in the classical setting: they are simple to describe, essential, and also serve as a linchpin for demonstrating equivalence between primitives.

Lorenzo Grassi, Silvia Onofri, Marco Pedicini, Luca Sozzi

Motivated by new applications such as secure Multi-Party Computation (MPC), Fully Homomorphic Encryption (FHE), and Zero-Knowledge proofs (ZK), many MPC-, FHE- and ZK-friendly symmetric-key primitives that minimize the number of multiplications over Fp for a large prime p have been recently proposed in the literature. This goal is often achieved by instantiating the non-linear layer via power maps x↦xd. In this paper, we start an analysis of new non-linear permutation functions over Fnp that can be used as building blocks in such symmetrickey primitives. Given a local map F : Fmp→ Fp, we limit ourselves to focus on S-Boxes over Fnp for n ≥ m defined as SF (x0, x1, . . . , xn−1) = y0|y1| . . . |yn−1 where yi := F(xi, xi+1, . . . , xi+m−1). As main results, we prove that• given any quadratic function F : F2p→ Fp, the corresponding S-Box SF over Fnp for n ≥ 3 is never invertible;• similarly, given any quadratic function F : F3p → Fp, the corresponding S-Box SF over Fnp for n ≥ 5 is never invertible.Moreover, for each p ≥ 3, we present (1st) generalizations of the Lai-Massey construction over Fnp defined as before via functions F : Fmp → Fp for each n = m ≥ 2 and (2nd) (non-trivial) quadratic functions F : F3p → Fp such that SF over Fnp for n ∈ {3, 4} is invertible. As an open problem for future work, we conjecture that for each m ≥ 1 there exists a finite integer nmax(m) such that SF over Fnp defined as before via a quadratic function F : Fmp →Fp is not invertible for each n ≥ nmax(m). Finally, as a concrete application, we propose Neptune, a variant of the sponge hash function Poseidon, whose non-linear layer is designed by taking into account the results presented in this paper. We show that this variant leads to a concrete multiplication reduction with respect to Poseidon.

K. Vidya, Hussain Imthiaz Hussain, Vishal Celestine, V. Siva Kumar · 5 authors

Abstract Crowdfunding is a method of raising funds from a large number of individuals or businesses. Investors can contribute to any project they are interested in and earn if the initiative is successful. Many crowdfunding sites now exist, and they accept large sums of money from investors and contributors and then leave them with bogus promises. Blockchain-based crowdfunding alters the usual approach to company finance. Generally, when people need to acquire funds to start a firm, they must first develop a strategy, statistical surveys, and models, and then offer their ideas to attract people or organisations. Banks, individual investors, and venture capital firms were among the sources of funding. The modern crowdfunding concept is based on three types of on-screen characters: the task initiator who presents the idea or venture to be financed, individuals or investors who invest in the idea, and a platform that connects these two characters to make the venture successful. It can be used to fund a wide range of start-ups and new concepts, such as inventive activities, medical improvements, travel, and social commercial enterprise projects. This work presents a practical implementation of a crowdfunding application that is secured by a lattice-based cryptosystem for encryption of user data and zero-knowledge proof for the identification of application users. Additionally, machine learning has been used for prediction of campaign success for the benefit of fund contributors.