Blockchain Papers

Md Akram, Anshuman Sen

The Banking, Financial Services, and Insurance (BFSI) sector represents a significant portion of any developing or developed economies of the world involving all banking, insurance, and non-banking financial institutions. This sector is the biggest buyer of identity management technology solutions and services. This accentuates the pivotal role of a robust identity authentication mechanism in the BFSI sector. The rapid proliferation of digitization in the different financial sectors, disruptive technological innovations around different services, and everchanging user behaviors are revolutionizing the way in which the institution of this sector interacts with their customers, employees, and other stakeholders. The definition of great consumer experience has widened in scope and includes facets like consumer trust, security, real-time, etc. The traditional identity verification system like passwords, pins, biometrics, facial recognition, etc. are prone to vulnerabilities. Blockchain addresses the lacunas in the present system by using a decentralized approach to transform digital identity. The purpose of this research paper is to study the use of blockchain in digital identity verification, the benefits it brings to identity management, and different techno-commercial use cases. This paper will also examine the zero-knowledge proof and the role of cryptography. For this study, a case study technique was used, in which different use cases of blockchain for digital identity management in the BFSI sector have been analyzed. Academics, practitioners, and government officials will benefit from the research article in investigating, implementing, and developing solutions for digital identity verification using blockchain.

Randhir Kumar, Prabhat Kumar, Rakesh Tripathi, Govind P. Gupta · 6 authors

The industrial healthcaresystem has enabled the possibility of realizing advanced real-time monitoring of patients and enriched the quality of medical services through data sharing among intelligent wearable devices and sensors. However, this connectivity brings the intrinsic vulnerabilities related to security and privacy due to the need of continuous communication and monitoring over public network (insecure channel). Motivated from the aforementioned discussions, we integrate permissioned blockchain and smart contract with deep learning (DL) techniques to design a novel secure and efficient data sharing framework named PBDL. Specifically, PBDL first has a blockchain scheme to register, verify (using zero-knowledge proof), and validate the communicating entities using the smart contract-based consensus mechanism. Second, the authenticated data are used to propose a novel DL scheme that combines stacked sparse variational autoencoder (SSVAE) with self-attention-based bidirectional long short term memory (SA-BiLSTM). In this scheme, SSVAE encodes or transforms the healthcare data into new format, and SA-BiLSTM identifies and improves the attack detection process. The security analysis and experimental results using IoT-Botnet and ToN-IoT datasets confirm the superiority of the PBDL framework over existing state-of-the-art techniques.

Yangzhou Cao, Jiageng Chen, Yajun Cao

In this study, we propose a blockchain-based privacy-preserving vaccine passport system for the global prevention and control of infectious diseases. The system operates a double-chain framework which consists of a public blockchain and a consortium blockchain. Among them, the combination of the immutability of the public blockchain and Internet of Things (IoT) technology in the supply chain ensures the openness and transparency of the cold chain logistics records of the vaccines covering the stages from auditing to the target vaccination hospitals. The system adopts the consortium blockchain to achieve the balance between the protection of users’ vaccination privacy and auditing by the government departments. Specifically, a distributed system-based threshold signature is adopted in the vaccine qualification phase to resist collusion between the vaccine manufacturing company and vaccine approval institutions. The cryptographic tools such as the anonymous credentials, zero-knowledge protocols, and range proofs ensure that users do not disclose any private information other than proving that they have a legally valid vaccine passport when users display the vaccine passports to customs. At the same time, customs can apply various vaccine prevention policies based on the conditions on the specific vaccine passports. Regarding the security properties of the system, a formal security model is given along with the corresponding security proofs.

Yangxu Song, Frank Jiang, Syed Wajid Ali Shah, Robin Doss

With the development of 5G networking technology on the Internet of Vehicle (IoV), there are new opportunities for numerous cyber-attacks, such as in-vehicle attacks like hijacking occurrences and data theft. While numerous attempts have been made to protect against the potential attacks, there are still many unsolved problems such as developing a fine-grained access control system. This is reflected by the granularity of security as well as the related data that are hosted on these platforms. Among the most notable trends is the increased usage of smart devices, IoV, cloud services, emerging technologies aim at accessing, storing and processing data. Most popular authentication protocols rely on knowledge-factor for authentication that is infamously known to be vulnerable to subversions. Recently, the zero-trust framework has drawn huge attention; there is an urgent need to develop further the existing Continuous Authentication (CA) technique to achieve the zero-trustiness framework. In this paper, firstly, we develop the static authentication process and propose a secured protocol to generate the smart key for user to unlock the vehicle. Then, we proposed a novel and secure continuous authentication system for IoVs. We present the proof-of-concept of our CA scheme by building a prototype that leverages the commodity fingerprint sensors, NFC, and smartphone. Our evaluations in real-world settings demonstrate the appropriateness of CA scheme and security analysis of our proposed protocol for digital key suggests its enhanced security against the known attack-vector.

Johannes Sedlmeir, Jonathan Lautenschlager, Gilbert Fridgen, Nils Urbach

Abstract This position paper discusses the challenges of blockchain applications in businesses and the public sector related to an excessive degree of transparency. We first point out the types of sensitive data involved in different patterns of blockchain use cases. We then argue that the implications of blockchains’ information exposure caused by replicated transaction storage and execution go well beyond the often-mentioned conflicts with the GDPR’s “right to be forgotten” and may be more problematic than anticipated. In particular, we illustrate the trade-off between protecting sensitive information and increasing process efficiency through smart contracts. We also explore to which extent permissioned blockchains and novel applications of cryptographic technologies such as self-sovereign identities and zero-knowledge proofs can help overcome the transparency challenge and thus act as catalysts for blockchain adoption and diffusion in organizations.

Jing Pan, Jiang Zhang, Fangguo Zhang, Xiaofeng Chen · 5 authors

No abstract is available for this record.

Peter R. Killeen

You need to transfer heat from one fluid at 100°C to another at 0°C without mixing them. Given some tubing, you could wrap one length around another. Then, with enough wound tubing, pumping both in at one end, at the nether end you would find that both fluids came out at about 50°C. Good.Can you do better? Can Nature? This is the nut of one (and thereafter many) of the problems Knut Schmidt-Nielsen (of Norwegian lineage, if you wondered; with a statue of him gazing at a camel on the Duke campus, if you wanted to wonder) was driven to by a sojourn in Arizona Sonoran desert half a century ago. There his naturalist's eyes found surprisingly abundant wildlife given the rigor of the environment. Consider the lowly kangaroo rat. It never drinks water and has no appetite for moisture-rich greens. But like all of us, the rat must breathe, and that means exhaling air saturated with moisture that he can scarce afford to lose. Warm air carries more water than does cool. Perhaps those clever little rodents used your tubing architecture to pass incoming and outgoing air by each other, so the outgoing air wasn't so warm, and with a few sniffles of the condensing cooler air the rat could regain some drops of what would be lost. That would be good. But Nature invented a way, and reinvented it dozens of times, that does better.Switch the input of one of your tubes to the nether end. Hot air coming in would then meet outgoing air just a little less hot than it and raise temperature a bit more, and so on down the tubes, until at the end, the now relatively cold incoming air would meet the almost equally cold outgoing, and the transfer of heat would be almost perfect. 100° is squandered on heating 0° but is well spent on 90°. This is called countercurrent exchange (CCE), here countercurrent heat exchange. I shall be mentioning a number of neat ideas that have some generality in this review. I call them cachets.1 They are terms of art that compress an intriguing idea into a simple expression. Words that you can drop at a party.2 You can think with them. Knut plots the temperature of exhalation from a dozen species of birds, and it is a linear function of ambient temperature—but always significantly below body temperature. Those little kangaroo rats do it even better than the birds, and he shows why with cross-sections of their sinuses. Knut is smarter than I, as he can generate a mathematical model of the process, which performs quite well. He is also wiser than I, as he does not write the equations of the model, just describes how it works.What these littlest of nature's mammals do, the biggest can too. How do whales not lose all their core heat through those fins and flukes, which are perfect radiators fanning frigid waters? CCE: They warm the incoming blood with the outgoing, so when the blood gets to the fins it is near their chilly temperature, and the blood returning from the fins is warmed to about core temperature. This clever design is no fluke; evolution works miracles!The brain needs stable temperatures. How do you keep a cool head in hot times? You've already guessed it: CCE, as the carotids spread out in a mesh (called a rete) passing its blood against the flow of venous blood coming in from the nasal sinuses, which cools it as necessary, before sending it on to the brain. Farther down a man's body another organ needs to be kept cool despite how hot he is; CCE to the rescue!Fireplaces are romantic, but most of the heat that is not made on the couch goes up the chimney. The Franklin stove is more efficient, as the stove box and chimney pipe radiate heat into the room. But while heating your front, it chills your back, because it must draw in cold air to feed the flames, and that comes from outside your house. A psychology graduate student improved the situation with countercurrent heat exchange. Close your eyes now before reading on, and see if you can figure out how. Now open them.3CCE works great to preserve the milieu intérieur. But what if you want to move some of that milieu extérieur? Suppose that, unlike the whales, you need to lose heat? Breathing in and out through the nose would tend to conserve your body heat. If you were a dog, what would you do? Perhaps find a way for the hot air to exit other than the one used by the cooler air coming in. In my Sonoran desert my Lucy spends a lot of her time panting. The nose is the primary cooler, inhaling; that long dripping tongue is merely a secondary heat exchange, designed primarily to amuse and bemuse you as it exhales through the mouth.You may have watched your dog pant, but have you noticed that she does not increase the frequency of panting as she gets hotter? This is what the engineers call bang-bang control4: It is either on or off. Why is frequency not a smooth function of temperature? Think about it for a moment before reading the answer suggested by a student of Knut's.5 Mammals cannot use CCE to increase the oxygenation of their blood from the air they breathe, but birds can, and fish breathing through gills use CCE to extract 80–90% of the oxygen that flows over them. “It was during the work with the ostrich that the need for further understanding of bird respiration became acute” is the type of sentence that regularly charms you in How Animals Work. Dogs pant at resonant frequencies; do large birds tune their breathing tracts and wingbeat so that breathing and flying are synchronized?A colleague designed a charter school decades ago in which he used CCE for knowledge exchange, having more advanced students tutor the less advanced throughout the grades. It is still in operation. To what novel uses might you put CCE?There is a mechanism similar to CCE, called countercurrent multipliers (CCMs), where a solution is concentrated “uphill,” as the kidneys concentrate urine. I shall let you turn to Knut for explication of this and other questions. But before you turn, ponder how you might design a CCM and for what else it might be a cachet.In looking through the book you will come across many straight lines, often in double-log coordinates. These are scaling laws. The cost of running in animals ranging from the white mouse to a horse is a near perfect power function (slope −0.40) of their body weight. There are many such scaling laws in biology, typically power functions, and often their observed slope can be derived rationally (West, Brown, & Enquist, 1997) or readily interpreted. A fascinating recent book about such laws is Scale: The Universal Laws of Life, Growth, and Death in Organisms, Cities, and Companies (West, 2017). He delivers on the promise of the subtitle. Question: Do psychologists’ favorite power functions, the psychophysicist's sensory scaling laws, and the behaviorist's generalized matching law fit into any of these schemes?An early observation of scaling laws at work was given by biologist J. B. S. Haldane: “You can drop a mouse down a thousand-yard mine shaft and, on arriving at the bottom, it gets a slight shock and walks away. A rat is killed, a man is broken, a horse splashes.” As the length of an animal doubles, its surface is squared and its mass is cubed. Your cachet: “the square–cube law.” The mass, and thus the kinetic energy that must be dissipated by the animal, increases as the cube of its length, but its landing or impact surface increases only as its square. The strength of bones increases with their cross-sectional area, whereas the mass they must support increases with the volume of the animal. Thus, ants can have very skinny legs, but elephants must have huge columns of legs. Gullivers just can't travel. HO-scale model trains are 1/87 the length of a real train. Their mass is thus 87–3 that of the real train. Less weight to hold them on the track, so they more readily flip at just a few feet per second, with linearly proportional wheel flanges of little help.Gas exchange is a surface phenomenon and so varies as the square of the length of an animal, but the mass it needs to service grows as the cube of the length. What are the design features of our lungs that help deal with his disparity? Drugs are absorbed as a function of the area they come in contact with, about the square of body length, but the mass that they must serve increases as its cube; good dosing requires knowledge of the square–cube law. But metabolic rate is another factor, and that decreases uniformly with body weight; drugs are slower to clear in a large animal, as Knut's story about dosing an elephant6 revealed. Because of this metabolic scaling, all species live for the same number of heartbeats.7 In prescribing a novel drug, my physician looked it up in the pharmacopeia, looked at me up and down, and asked, “I need to dose this in proportion to your skin area. Do you know what that is, Peter?” I just grinned and shook my head, and “No” was all I said.Someone challenges you to draw a curve from point A to point B below it and to its right, so that a frictionless ball rolling from A to B would get there faster than along any other curve. (Hint: This is a situation where CCE won't help.) What would you draw? A straight ramp? A semicircle? A catenary? This optimization problem had bemused good mathematicians for several years. Galileo thought, but couldn't prove (because the calculus was not yet invented), that it was a parabola (close but wrong). In 1696 Johann Bernoulli, one of a clan of gifted Swiss mathematicians, posed it as a challenge to the world (the small world of 17th-century mathematicians). Johann had the correct answer (but with a flawed derivation), which took him weeks to arrive at, in his back pocket, yet he had to extend the deadline because of the paucity of returns. In the end, six great mathematicians provided answers: Johann Bernoulli, Newton, Jakob8 Bernoulli, Leibniz, Tschirnhauß, and l'Hôpital. When Newton eventually found the problem in his post, he completed his proof overnight (taking longer than he would have in his prime) and submitted it anonymously.9 When Bernoulli saw it, he said he knew it surely to be Newton's solution, just “as one knows the lion by its claw.” The correct answer was a segment of a cycloid, the curve traced by a point on a circle rolling along a line. One of the solutions evolved into the calculus of variations, which tells us what kinds of functions, or curves, satisfy a minimum or maximum—a big brother to the simple calculus you may have met in high school.Alexander uses the calculus of variations to prove that the shortest distance between two points is a straight line. Why prove the obvious? To sharpen our pencils. But he starts simpler, first reviewing high school calculus by using homely examples, such as the optimal shape for a can to minimize the metal used to contain a particular volume. Any guesses?10 He wryly notes that most of the cans in his grocery store do not satisfy this solution: “They may have been applying some other optimization criterion.” This, the “optimal for what?” question, is a recurrent issue in optimality theory. What is the optimal speed for an airplane? Given the relation between power used and air resistance and lift, Alexander provides a solution for minimal power between two airports. Then he derives another for minimal fuel: If you fly a bit faster, using more power, you get there sooner, using less fuel. What is optimal depends on what variables you are talking about. What is the optimal lifestyle: fast and furious and everything goes, or calm, centered, and academic? Husband the candle or burn it at both ends? “Optimal for what?” is the question that you are starting to learn to ask.As Alexander explains, calculus is the tool of choice for optimization, and it typically involves some variant of taking the derivative of a function and setting it to zero. However, that gives you an extremum, which could be either a maximum or a minimum. You need to check which, and there are several straightforward techniques to do so (e.g., take the second derivative at that point. If it is positive, the curve is going up from there, and you are at a minimum; negative, at a maximum). If you are sometimes embarrassed by your mathematical mistakes, join the crowd. Some designers of an early flying wing aircraft, precursor to the B2, concluded that you maximized range if all the weight of the craft was in the wings. Eventually the contract was canceled because of inadequate range (“insufficient funds” is what the press release originally said after 15 aircraft were built). A subsequent investigator found that the extremum in this case was a minimum, not a maximum; the designers had apparently failed to check the second derivative and designed the worst, not best, possible configuration! They were “embarrassed” by their mistake but refused to step back from the design, on which the B2 was based (Biddle, 1989). They redesigned their claim instead, arguing that it optimized other objectives. (It didn't.) The B2 incurred billions of dollars in redesign. Clearly those designers were optimizing their claims over objectives other than the best aircraft design to maximize range.11After analyzing optimized structures such as bones and eggshells, Alexander turns to motion: walking, running, flying, and leaping. He shows the utility of catastrophe theory, at least qualitatively, in the analysis of gaits. He slowly ponders the order in which tortoises should move their feet. Of most interest to this audience is his review of optimal foraging: In selecting prey, should a bird eat only the biggest worms or anything it comes to? How long should a carnivore pick over a carcass before moving on? When should a challenged stag fight and when should it run? You have already mused over the relevant variables, I'm sure. 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Léo Robert, Daiki Miyahara, Pascal Lafourcade, Takaaki Mizuki

Abstract During the last years, several card-based Zero-Knowledge Proof (ZKP) protocols for Nikoli’s puzzles have been designed. Although there are relatively simple card-based ZKP protocols for a number of puzzles, such as Sudoku and Kakuro, some puzzles face difficulties in designing simple protocols. For example, Slitherlink requires novel and elaborate techniques to construct a protocol. In this study, we focus on three Nikoli puzzles: Nurikabe, Hitori, and Heyawake. To date, no card-based ZKP protocol for these puzzles has been developed, partially because they have a relatively tricky rule that colored cells should form a connected area (namely a polyomino); this rule, sometimes referred to as “Bundan-kin” (in Japanese), complicates the puzzles, as well as facilitating difficulties in designing card-based ZKP protocols. We address this challenging task and propose a method for verifying the connectivity of hidden colored cells in a ZKP manner, such that we construct card-based ZKP protocols for the three puzzles.

Rand Mohammed Rafee, Bashar M. Nema

A secure electronic learning platform has been created to enable teachers and students to log into their accounts to learn efficiently and safely at any place and time. This platform has been proposed due to the urgent need to develop the education system and move it from traditional to interactive e-learning. In this paper, an application implemented that access remotely using a web browser interface and saved on a server depends on a Zero-Knowledge Proof (ZKP) system with an RSA algorithm was employed to solve registration and login challenges and securely transfer passwords. Using adapted AES to encrypt each user's personal information, Exams, and save it in in encrypted form in the database. The simulated results in this paper indicate the existence of a secure e-learning system, where security was achieved by performing the registration and login process without sending the password in its explicit form over an insecure network such as the Internet, in addition to encrypting the necessary information to be stored in an incomprehensible manner in the database, in the case of presence of an attack on the database.

E. Jansirani, N. Kowsalya

Data security plays a major role in computer network. Because it helps to transmit data in secure way over the Internet. So we need to use strong security method for secure data transaction. Cryptography is a security tool which helps to transmit information from one place to another place over computer network. Cryptography follows encryption and decryption methods for data transmission. Cryptographic technique is completely based on key generation because it needs keys to transmit data between users. However cryptography works well in secure data transmission but it needs keys to provide security for data. In cryptography generation of keys taking more time than transmission of data. So in this paper we discuss about Zero-Knowledge Proof (ZKP) which is also based on cryptographic technique. ZKP is also useful in secure data transmission without sharing key values between users. This paper tells about overview of ZKP and how it is useful in data transmission.

Wenzheng Zhang, Shiyun Liu, Zhe Xia

No abstract is available for this record.

Muhammad ElSheikh, Amr Youssef

The Open Vote Network is a self-tallying decentralized e-voting protocol suitable for boardroom elections. Currently, it has two Ethereum-based implementations: the first, by McCorry et al., has a scalability issue since all the computations are performed on-chain. The second implementation, by Seifelnasr et al., solves this issue partially by assigning a part of the heavy computations to an off-chain untrusted administrator in a verifiable manner. As a side effect, this second implementation became not dispute-free; there is a need for a tally dispute phase where an observer interrupts the protocol when the administrator cheats, i.e., announces a wrong tally result. In this work, we propose a new smart contract design to tackle the problems in the previous implementations by (i) preforming all the heavy computations off-chain hence achieving higher scalability, and (ii) utilizing zero-knowledge Succinct Non-interactive Argument of Knowledge (zk-SNARK) to verify the correctness of the off-chain computations, hence maintaining the dispute-free property. To demonstrate the effectiveness of our design, we develop prototype implementations on Ethereum and conduct multiple experiments for different implementation options that show a trade-off between the zk-SNARK proof generation time and the smart contract gas cost, including an implementation in which the smart contract consumes a constant amount of gas independent of the number of voters.

Aarushi Goel, Matthew Green, Mathias Hall-Andersen, Gabriel Kaptchuk

Abstract Set membership proofs are an invaluable part of privacy preserving systems. These proofs allow a prover to demonstrate knowledge of a witness w corresponding to a secret element x of a public set, such that they jointly satisfy a given NP relation, i.e. ℛ( w, x ) = 1 and x is a member of a public set { x 1 , . . . , x 𝓁 }. This allows the identity of the prover to remain hidden, eg. ring signatures and confidential transactions in cryptocurrencies. In this work, we develop a new technique for efficiently adding logarithmic-sized set membership proofs to any MPC-in-the-head based zero-knowledge protocol (Ishai et al. [STOC’07]). We integrate our technique into an open source implementation of the state-of-the-art, post quantum secure zero-knowledge protocol of Katz et al. [CCS’18].We find that using our techniques to construct ring signatures results in signatures (based only on symmetric key primitives) that are between 5 and 10 times smaller than state-of-the-art techniques based on the same assumptions. We also show that our techniques can be used to efficiently construct post-quantum secure RingCT from only symmetric key primitives.

Pankaj Dayama, Arpita Patra, Protik Paul, Nitin Singh · 5 authors

Abstract Traditional zero-knowledge protocols have been studied and optimized for the setting where a single prover holds the complete witness and tries to convince a verifier about a predicate on the witness, without revealing any additional information to the verifier. In this work, we study the notion of distributed-prover zero knowledge (DPZK) for arbitrary predicates where the witness is shared among multiple mutually distrusting provers and they want to convince a verifier that their shares together satisfy the predicate. We make the following contributions to the notion of distributed proof generation: (i) we propose a new MPC-style security definition to capture the adversarial settings possible for different collusion models between the provers and the verifier, (ii) we discuss new efficiency parameters for distributed proof generation such as the number of rounds of interaction and the amount of communication among the provers, and (iii) we propose a compiler that realizes distributed proof generation from the zero-knowledge protocols in the Interactive Oracle Proofs (IOP) paradigm. Our compiler can be used to obtain DPZK from arbitrary IOP protocols, but the concrete efficiency overheads are substantial in general. To this end, we contribute (iv) a new zero-knowledge IOP Graphene which can be compiled into an efficient DPZK protocol. The (D + 1)-DPZK protocol D-Graphene, with D provers and one verifier, admits O ( N 1 /c ) proof size with a communication complexity of O (D 2 ·( N 1−2 /c + N s )), where N is the number of gates in the arithmetic circuit representing the predicate and N s is the number of wires that depends on inputs from two or more parties. Significantly, only the distributed proof generation in D-Graphene requires interaction among the provers. D-Graphene compares favourably with the DPZK protocols obtained from the state-of-art zero-knowledge protocols, even those not modelled as IOPs.

Han Zhang, Suyi Yang, Hongqing Zhu

No abstract is available for this record.

Xin Liu, Bin Zhang

In an oblivious transfer with access control (AC-OT) scheme, the database provider (DBP) can define different access control policies for each data record, and users are allowed to hide their choices from the DBP when accessing data. An accountable AC-OT (AAC-OT) scheme is an enhanced version of AC-OT that allows the DBP to revoke the access rights of malicious users. However, existing AAC-OT schemes have defects in their security model definition, malicious user revocation mechanism, and user-side performance. Therefore, the authors proposed an improved AAC-OT scheme that applies to the public cloud environment. In the definition of the security model, the definitions of access authorization and revocation are considered. By modifying the user tracing mechanism, the DBP can independently revoke the access rights of fraudulent users. In addition, the number of bilinear pairing operations performed by users in the transfer phase is kept constant by optimizing the generation of the underlying zero-knowledge proofs.

Cheng Huang, Liang Xue, Dongxiao Liu, Xuemin Shen · 7 authors

Secure cross-domain authorization and authentication (AA) enable application service providers (ASPs) to allow users for resource access from different trusted domains. In this article, we propose a unified blockchain-assisted secure cross-domain AA framework for smart city, which can guarantee transparent cross-domain resource access while preserving user privacy. In the framework, ASPs can flexibly delegate their authentication capabilities to the blockchain, and users authorized by different ASPs can be authenticated by the blockchain where the authentication events are publicly audited and traced. Since the blockchain is publicly accessible, users’ sensitive identity attributes may be exposed during the authentication process. To address privacy leakage caused by the authentication events, several privacy-preserving techniques, including threshold-based homomorphic encryption, zero-knowledge proof, and random permutation, are exploited to hide users’ sensitive information on the blockchain. Moreover, to improve user revocation efficiency, we integrate a cryptographic accumulator and secure hash functions into the framework where ASPs are allowed to revoke their users through a global revocation contract. Our security analysis shows that the proposed framework can achieve all desirable security and privacy properties, and a proof-of-concept prototype has been developed to demonstrate the correctness and efficiency of the proposed framework.

Cong Deng, Lin You, Xianghong Tang, Gengran Hu · 5 authors

Zero-Knowledge Proof is widely used in blockchains. For example, zk-SNARK is used in Zcash as its core technology to identifying transactions without the exposure of the actual transaction values. Up to now, various range proofs have been proposed, and their efficiency and range-flexibility have also been improved. Bootle et al. used the inner product method and recursion to construct an efficient Zero-Knowledge Proof in 2016. Later, Benediky Bünz et al. proposed an efficient range proof scheme called Bulletproofs, which can convince the verifier that a secret number lies in [0,2κ−1] with κ being a positive integer. By combining the inner-product and Lagrange’s four-square theorem, we propose a range proof scheme called Cuproof. Our Cuproof can make a range proof to show that a secret number v lies in an interval [a,b] with no exposure of the real value v or other extra information leakage about v. It is a good and practical method to protect privacy and information security. In Bulletproofs, the communication cost is 6+2logκ, while in our Cuproof, all the communication cost, the proving time and the verification time are of constant sizes.

Huaqun Guo, Xingjie Yu

Blockchain is a technology that has desirable features of decentralization, autonomy, integrity, immutability, verification, fault-tolerance, anonymity, auditability, and transparency. In this paper, we first carry out a deeper survey about blockchain technology, especially its history, consensus algorithms' quantitative comparisons, details of cryptography in terms of public key cryptography, Zero-Knowledge Proofs, and hash functions used in the blockchain, and the comprehensive list of blockchain applications. Further, the security of blockchain itself is a focus in this paper. In particular, we assess the blockchain security from risk analysis to derive comprehensive blockchain security risk categories, analyze the real attacks and bugs against blockchain, and summarize the recently developed security measures on blockchain. Finally, the challenges and research trends are presented to achieve more scalable and securer blockchain systems for the massive deployments.

M. X. Luo, Shao-Ming Fei, Jing‐Ling Chen

Quantum entanglement has shown distinguished features beyond any classical state. Many methods have been presented to verify unknown entanglement with the complete information about the density matrices by quantum state tomography. In this work, we aim to identify unknown entanglement with only partial information of the state space. The witness consists of a generalized Greenberger-Horne-Zeilinger-like paradox expressed by Pauli observables, and a nonlinear entanglement witness expressed by density matrix elements. First, we verify unknown bipartite entanglement and study the robustness of entanglement witnesses against the white noise. Second, we generalize such verification to partially unknown multipartite entangled states, including the Greenberger-Horne-Zeilinger-type and W-type states. Third, we give a quantum-information application related to the quantum zero-knowledge proof. It further provides a useful method in blindly verifying universal quantum computation resources. These results may be interesting in entanglement theories, quantum communication, and quantum networks.

Gurjot Singh Gaba, Mustapha Hedabou, Pardeep Kumar, An Braeken · 6 authors

No abstract is available for this record.

Zhiguo Wan, Yan Zhou, Kui Ren

The emerging blockchain technology, combined with the smart contract paradigm, is expected to transform traditional applications with decentralization. When the blockchain technology is applied to decentralize traditional applications, blockchain validators may need to take in sensitiveoff-chaindata to execute a smart contract. On the one hand, decentralized applications (DApps) require authentic off-chain input data to correctly execute a given business procedure. On the other hand, users are reluctant to expose their sensitive privacy on the blockchain. For example, for a decentralized medical insurance DApp that takes as input personal health data, it is critical to guarantee authenticity and privacy of the data sent to the smart contract, such that the data can be verified by validators without leaking sensitive information. However, no satisfactory solution has been proposed to attain privacy and authenticity at the same time. In this work, we first present a highly efficient authenticated zero knowledge proof protocol called zk-DASNARK by extending the classical zk-SNARK scheme with data authentication. Based on zk-DASNARK, we design zk-AuthFeed, a zero-knowledge authenticated off-chain data feed scheme to achieve both data privacy and authenticity for blockchain-based DApps. Following the strategy of “compute off-chain and verify on-chain”, zk-AuthFeed can significantly reduce computation cost of blockchain validators. We fully implement a prototype of zk-AuthFeed, and conduct comprehensive experiments on a medical insurance DApp. We consider 4 typical computation models for insurance premium/reimbursement in the experiments. It shows that zk-AuthFeed is highly efficient: key generation takes about 10 seconds only, proof generation takes less than 4 seconds, and proof verification takes less than 40 ms.

Xavier Salleras, Sergi Cortiñas Rovira, Vanesa Daza

Nowadays, there are a plethora of services that are provided and paid for online, such as video streaming subscriptions, car-share, vehicle parking, purchasing tickets for events, etc. Online services usually issue tokens that are directly related to the identities of their users after they sign up to a platform; users need to authenticate themselves by using the same credentials each time they use the service. Likewise, when using in-person services, such as going to a concert, after paying for this service, the user usually receives a ticket, which proves that he/she has the right to use that service. In both scenarios, the main concerns surround the centralization of these systems and that they do not ensure customers’ privacy. The involved service providers are trusted third parties—authorities that offer services and handle private data about users. In this paper, we designed and implemented FORT, a decentralized system that allows customers to prove their rights to use specific services (either online or in-person) without revealing sensitive information. To achieve decentralization, we proposed a solution where all of the data are handled by a blockchain. We describe and uniquely identify users’ rights using non-fungible tokens (NFTs), and possession of these rights is demonstrated by using zero-knowledge proofs—cryptographic primitives that allow us to guarantee customers’ privacy. Furthermore, we provide benchmarks of FORT, which show that our protocol is efficient enough to be used in devices with low computing resources, such as smartphones or smartwatches, which are devices commonly used in our use case scenario.

Louis-Henri Merino, Simone Colombo, Rene D. Reyes-Bardales, Alaleh Azhir · 12 authors

Online voting is convenient and flexible, but amplifies the risks of voter coercion and vote buying. One promising mitigation strategy enables voters to give a coercer fake voting credentials, which silently cast votes that do not count. Current systems along these lines make problematic assumptions about credential issuance, however, such as strong trust in a registrar and/or in voter-controlled hardware, or expecting voters to interact with multiple registrars. Votegral is the first coercion-resistant voting architecture that leverages the physical security of in-person registration to address these credential-issuance challenges, amortizing the convenience costs of in-person registration by reusing credentials across successive elections. Votegral's registration component, TRIP, gives voters a kiosk in a privacy booth with which to print real and fake credentials on paper, eliminating dependence on trusted hardware in credential issuance. The voter learns and can verify in the privacy booth which credential is real, but real and fake credentials thereafter appear indistinguishable to others. Only voters actually under coercion, a hopefully-rare case, need to trust the kiosk. To achieve verifiability, each paper credential encodes an interactive zero-knowledge proof, which is sound in real credentials but unsound in fake credentials. Voters observe the difference in the order of printing steps, but need not understand the technical details. Experimental results with our prototype suggest that Votegral is practical and sufficiently scalable for real-world elections. User-visible latency of credential issuance in TRIP is at most 19.7 seconds even on resource-constrained kiosk hardware, making it suitable for registration at remote locations or on battery power. A companion usability study indicates that TRIP's usability is competitive with other e-voting systems including some lacking coercion resistance, and formal proofs support TRIP's combination of coercion-resistance and verifiability.