Blockchain Papers

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.

Zhengyi Jiang, Ferdian Jovan, Peiman Moradi, Tom Richardson · 8 authors

Abstract Offshore wind farms will play a vital role in the global ambition of net zero energy generation. Future offshore wind farms will be larger and further from the coast, meaning that traditional human‐based operations and maintenance approaches will become infeasible due to safety, cost, and skills shortages. The use of remotely operated or autonomous robotic assistants to undertake these activities provides an attractive alternative solution. This paper presents an autonomous multirobot system which is able to transport, deploy and retrieve a wind turbine blade inspection robot using an unmanned aerial vehicle (UAV). The proposed solution is a fully autonomous system including a robot deployment interface for deployment, a mechatronic link‐hook module (LHM) for retrieval, both installed on the underside of a UAV, a mechatronic on‐load attaching module installed on the robotic payload and an intelligent global mission planner. The LHM is integrated with a 2‐DOF hinge that can operate either passively or actively to reduce the swing motion of a slung load by approximately 30%. The mechatronic modules can be coupled and decoupled by special maneuvers of the UAV, and the intelligent global mission planner coordinates the operations of the UAV and the mechatronic modules for synchronous and seamless actions. For navigation in the vicinity of wind turbine blades, a visual‐based localization merged with the location knowledge from Global Navigation Satellite System has been developed. A proof‐of‐concept system was field tested on a full‐size decommissioned wind‐turbine blade. The results show that the experimental system is able to deploy and retrieve a robotic payload onto and from a wind turbine blade safely and robustly without the need for human intervention. The vicinity localization and navigation system have shown an accuracy of 0.65 and 0.44 m in the horizontal and vertical directions, respectively. Furthermore, this study shows the feasibility of systems toward autonomous inspection and maintenance of offshore windfarms.

Sinka Gao, Guo Qiang Li, Hong Fei Fu, Heng Zhang

Delphinus cross-chain aggregator is a universal firmware which synchronise states between different smart contracts on different block-chains. In the world of block-chains, synchronization challenges are two-folded. Firstly, contracts from different main block-chain can not communicate with each other which makes it hard to establish a trustworthy communication channel for them to share and maintain a universal state between each other. Secondly, transactions on different block-chains can hardly be ordered thus conflicts are common and we need a novel way to avoid and handle these conflicts. Delphinus cross-chain aggregator is a ZKSNARK based multi-block-chain layer on top of which rich cross chain applications can run safely and efficiently.

Matthias Babel, Vincent Gramlich, Marc-Fabian Körner, Johannes Sedlmeir · 6 authors

Abstract In the energy transition, there is an urgent need for decreasing overall carbon emissions. Against this background, the purposeful and verifiable tracing of emissions in the energy system is a crucial key element for promoting the deep decarbonization towards a net zero emission economy with a market-based approach. Such an effective tracing system requires end-to-end information flows that link carbon sources and sinks while keeping end consumers’ and businesses’ sensitive data confidential. In this paper, we illustrate how non-fungible tokens with fractional ownership can help to enable such a system, and how zero-knowledge proofs can address the related privacy issues associated with the fine-granular recording of stakeholders’ emission data. Thus, we contribute to designing a carbon emission tracing system that satisfies verifiability, distinguishability, fractional ownership, and privacy requirements. We implement a proof-of-concept for our approach and discuss its advantages compared to alternative centralized or decentralized architectures that have been proposed in the past. Based on a technical, data privacy, and economic analysis, we conclude that our approach is a more suitable technical backbone for end-to-end digital carbon emission tracing than previously suggested solutions.

Hongjian Yin, E Chen, Yan Zhu, Rongquan Feng · 5 authors

In this paper, we address the problem of secure decision of membership. We present a Zero-Knowledge Dual Membership Proof (ZKDMP) protocol, which can support positive and negative (Pos-and-Neg) membership decisions simultaneously. To do it, two secure aggregation functions are used to compact an arbitrarily-sized subset into an element in a cryptographic space. By using these aggregation functions, a subset can achieve a secure representation, and the representation size of the subsets is reduced to the theoretical lower limit. Moreover, the zeros-based and poles-based secure representation of the subset are used to decide Pos-and-Neg membership, respectively. We further verify the feasibility of combining these two secure representations of the subset, so this result is used to construct our dual membership decision cryptosystem. Specifically, our ZKDMP protocol is proposed for dual membership decisions, which can realize a cryptographic proof of strict Pos-and-Neg membership simultaneously. Furthermore, the zero-knowledge property of our construction ensures that the information of the tested element will not be leaked during the implementation of the protocol. In addition, we provide detailed security proof of our ZKDMP protocol, including positive completeness, negative completeness, soundness and zero-knowledge.

Xin Liu Xin Liu, Yang Xu Xin Liu, Gang Xu Yang Xu, Xiu-Bo Chen Gang Xu · 5 authors

<p>With the rapid development of the Internet and information technology, the problem of zero-trust networks has become increasingly prominent, and secure multi-party computation has become a research hotspot to solve the problem of zero-trust networks. The secure judgment of point and line relationship is an important research branch of secure computing set geometry. However, most of resent secure computing protocols of point and line relationship are designed in the semi-honest model and cannot resist malicious attacks. Therefore, this paper analyzes the possible malicious adversary behaviors and designs a secure protocol in the malicious model. In this paper, the Paillier cryptosystem, zero- knowledge proof, and cut-choose method are used to resist malicious behavior, and the real/ideal model paradigm method is used to prove the security of the protocol. Compared with the existing solutions, the malicious model protocol is still efficient and widely used in real applications.</p> <p> </p>

William J. Buchanan

Cryptography has proven to be one of the most contentious areas in modern society. For some it protects the rights of individuals to privacy and security, while for others it puts up barriers against the protection of our society. This book aims to develop a deep understanding of cryptography, and provide a way of understanding how privacy, identity provision and integrity can be enhanced with the usage of encryption. The book has many novel features including: • full provision of Web-based material on almost every topic covered • provision of additional on-line material, such as videos, source code, and labs • coverage of emerging areas such as Blockchain, Light-weight Cryptography and Zero-knowledge Proofs (ZKPs) Key areas covered include: • Fundamentals of Encryption • Public Key Encryption • Symmetric Key Encryption • Hashing Methods • Key Exchange Methods • Digital Certificates and Authentication • Tunneling • Crypto Cracking • Light-weight Cryptography • Blockchain • Zero-knowledge Proofs This book provides extensive support through the associated website of: http://asecuritysite.com/encryption

Nikos Fotiou, Iakovos Pittaras, Spiros Chadoulos, Vasilios A. Siris · 7 authors

As IoT becomes omnipresent vast amounts of data are generated, which can be used for building innovative applications. However,interoperability issues and security concerns, prevent harvesting the full potentials of these data. In this paper we consider the use case of data generated by smart buildings. Buildings are becoming ever "smarter" by integrating IoT devices that improve comfort through sensing and automation. However, these devices and their data are usually siloed in specific applications or manufacturers, even though they can be valuable for various interested stakeholders who provide different types of "over the top" services, e.g., energy management. Most data sharing techniques follow an "all or nothing" approach, creating significant security and privacy threats, when even partially revealed, privacy-preserving, data subsets can fuel innovative applications. With these in mind we develop a platform that enables controlled, privacy-preserving sharing of data items. Our system innovates in two directions: Firstly, it provides a framework for allowing discovery and selective disclosure of IoT data without violating their integrity. Secondly, it provides a user-friendly, intuitive mechanisms allowing efficient, fine-grained access control over the shared data. Our solution leverages recent advances in the areas of Self-Sovereign Identities, Verifiable Credentials, and Zero-Knowledge Proofs, and it integrates them in a platform that combines the industry-standard authorization framework OAuth 2.0 and the Web of Things specifications.

Felix Engelmann, Thomas Kerber, Markulf Kohlweiss, Mikhail Volkhov

Privacy-oriented cryptocurrencies, like Zcash or Monero, provide fair transaction anonymity and confidentiality, but lack important features compared to fully public systems, like Ethereum. Specifically, supporting assets of multiple types and providing a mechanism to atomically exchange them, which is critical for e.g. decentralized finance (DeFi), is challenging in the private setting. By combining insights and security properties from Zcash and SwapCT (PETS 21, an atomic swap system for Monero), we present a simple zk-SNARKs based transaction scheme, called Zswap, which is carefully malleable to allow the merging of transactions, while preserving anonymity. Our protocol enables multiple assets and atomic exchanges by making use of sparse homomorphic commitments with aggregated open randomness, together with Zcash friendly simulation-extractable non-interactive zero-knowledge (NIZK) proofs. This results in a provably secure privacypreserving transaction protocol, with efficient swaps, and overall performance close to that of existing deployed private cryptocurrencies. It is similar to Zcash Sapling and benefits from existing code-bases and implementation expertise.

Foteini Baldimtsi, Panagiotis Chatzigiannis, Steven Gordon, Phi Hung Le · 5 authors

We present gOTzilla, a protocol for interactive zero-knowledge proofs for very large disjunctive statements of the following format: given publicly known circuit C, and set of values Y = {y1 , . . . , yn }, prove knowledge of a witness x such that C(x) = y1 ∨ C(x) = y2 ∨ · · · ∨ C(x) = yn . These type of statements are extremely important for the proof of assets (PoA) problem in cryptocurrencies where a prover wants to prove the knowledge of a secret key sk that associates with the hash of a public key H(pk) posted on the ledger. We note that the size of n in popular cryptocurrencies, such as Bitcoin, is estimated to 80 million. For the construction of gOTzilla, we start by observing that if we restructure the proof statement to an equivalent of proving knowledge of (x, y) such that (C(x) = y) ∧ (y = y1 ∨ · · · ∨ y = yn )), then we can reduce the disjunction of equalities to 1-out-of-N oblivious transfer (OT). Our overall protocol is based on the MPC in the head (MPCitH) paradigm. We additionally provide a concrete, efficient extension of our protocol for the case where C combines algebraic and non-algebraic statements (which is the case in the PoA application). We achieve an asymptotic communication cost of O(log n) plus the proof size of the underlying MPCitH protocol. While related work has similar asymptotic complexity, our approach results in concrete performance improvements. We implement our protocol and provide benchmarks. Concretely, for a set of size 1 million entries, the total run-time of our protocol is 14.89 seconds using 48 threads, with 6.18 MB total communication, which is about 4x faster compared to the state of the art when considering a disjunctive statement with algebraic and non-algebraic elements.

Wenxuan Yu, Minghui Xu, Dongxiao Yu, Xiuzhen Cheng · 6 authors

Payment channel network (PCN) is a layer-two scaling solution that enables fast off-chain transactions but does not involve on-chain transaction settlement. PCNs raise new privacy issues including balance secrecy, relationship anonymity and payment privacy. Moreover, protecting privacy causes low transaction success rates. To address this dilemma, we propose zk-PCN, a privacy-preserving payment channel network using zk-SNARKs. We prevent from exposing true balances by setting up \textit{public balances} instead. Using public balances, zk-PCN can guarantee high transaction success rates and protect PCN privacy with zero-knowledge proofs. Additionally, zk-PCN is compatible with the existing routing algorithms of PCNs. To support such compatibility, we propose zk-IPCN to improve zk-PCN with a novel proof generation (RPG) algorithm. zk-IPCN reduces the overheads of storing channel information and lowers the frequency of generating zero-knowledge proofs. Finally, extensive simulations demonstrate the effectiveness and efficiency of zk-PCN in various settings.

Ari Biswas, Graham Cormode

Differential Privacy (DP) is often presented as a strong privacy-enhancing technology with broad applicability and advocated as a de facto standard for releasing aggregate statistics on sensitive data. However, in many embodiments, DP introduces a new attack surface: a malicious entity entrusted with releasing statistics could manipulate the results and use the randomness of DP as a convenient smokescreen to mask its nefariousness. Since revealing the random noise would obviate the purpose of introducing it, the miscreant may have a perfect alibi. To close this loophole, we introduce the idea of Interactive Proofs For Differential Privacy, which requires the publishing entity to output a zero knowledge proof that convinces an efficient verifier that the output is both DP and reliable. Such a definition might seem unachievable, as a verifier must validate that DP randomness was generated faithfully without learning anything about the randomness itself. We resolve this paradox by carefully mixing private and public randomness to compute verifiable DP counting queries with theoretical guarantees and show that it is also practical for real-world deployment. We also demonstrate that computational assumptions are necessary by showing a separation between information-theoretic DP and computational DP under our definition of verifiability.

Movsowitz Davidow, Danielle, Manevich, Yacov, Toch, Eran

Differential Privacy (DP) is often presented as a strong privacy-enhancing technology with broad applicability and advocated as a de-facto standard for releasing aggregate statistics on sensitive data. However, in many embodiments, DP introduces a new attack surface: a malicious entity entrusted with releasing statistics could manipulate the results and use the randomness of DP as a convenient smokescreen to mask its nefariousness. Since revealing the random noise would obviate the purpose of introducing it, the miscreant may have a perfect alibi. To close this loophole, we introduce the idea of \textit{Verifiable Differential Privacy}, which requires the publishing entity to output a zero-knowledge proof that convinces an efficient verifier that the output is both DP and reliable. Such a definition might seem unachievable, as a verifier must validate that DP randomness was generated faithfully without learning anything about the randomness itself. We resolve this paradox by carefully mixing private and public randomness to compute verifiable DP counting queries with theoretical guarantees and show that it is also practical for real-world deployment. We also demonstrate that computational assumptions are necessary by showing a separation between information-theoretic DP and computational DP under our definition of verifiability.

George Morris William Tangka, Ellie Ophelia Delviolin, Hsien-Ming Chou

E-commerce plays a significant role in a country's economic condition. Since the COVID-19 outbreak, it has become more popular, along with concerns about its ability to handle information security. The Zero-Knowledge Proof (ZKP) method could be a possible solution to the e-commerce payment security issue that hampers customer trust. This paper investigates the viability of an online payment framework based on the ZPK method. This method is an upgrade for authentication during the payment process in online shopping. Experiments on customers' perspectives of the payment framework based on the ZKP method were conducted and supported the perceived usefulness, ease of use, trust, control, satisfaction, and loyalty aspects of a better e-commerce website. It allows advantages for both customers and e-commerce and prevents fraud, which will increase the trust level for both sides. zkSNARK speeds up and lowers the cost of the process, but there is a risk of DOS. Future work needs to be done to handle DOS in this method.

Rajani Singh, Ashutosh Dhar Dwivedi, Raghava Rao Mukkamala, Waleed S. Alnumay

In recent years, decentralized applications such as Distributed Ledger Technologies and blockchain have evolved as suitable applications for secure sharing of information in a decentralized fashion using privacy preserving techniques like zero-knowledge protocols. However, the biggest issue with the traditional zero-knowledge protocols on a blockchain ledger is their slow performance on big data. This paper presents the advance zero-knowledge ledger by replacing their range-proof technique with the most efficient range-proof technique based on the improved inner product based zero-knowledge proofs. Moreover, this technique allows the aggregation of multiple range-proofs into a single range-proof, which makes the current zero-knowledge ledger system more efficient than the existing one.

Yang Yang, Shangbin Han, Ping Xie, Yan Zhu · 8 authors

With the increasing demand for privacy protection in the blockchain, the universal zero-knowledge proof protocol has been developed and widely used. Because hash function is an important cryptographic primitive in a blockchain, the zero-knowledge proof of hash preimage has a wide range of application scenarios. However, it is hard to implement it due to the transformation of efficiency and execution complexity. Currently, there are only zero-knowledge proof circuits of some widely used hash functions that have been implemented, such as SHA256. SM3 is a Chinese hash function standard published by the Chinese Commercial Cryptography Administration Office for the use of electronic authentication service systems, and hence might be used in several cryptographic applications in China. As the national cryptographic hash function standard, the zero-knowledge proof circuit of SM3 (Chinese Commercial Cryptography) has not been implemented. Therefore, this paper analyzed the SM3 algorithm process, designed a new layered circuit structure, and implemented the SM3 hash preimage zero-knowledge proof circuit with a circuit size reduced by half compared to the automatic generator. Moreover, we proposed several extended practical protocols based on the SM3 zero-knowledge proof circuit, which is widely used in blockchain.

Aritra Banerjee, Hitesh Tewari

The evolution of smart contracts in recent years inspired a crucial question: do smart contract evaluation protocols provide the required level of privacy when executing contracts on the blockchain? The Hawk (IEEE S&P ’16) paper introduces a way to solve the problem of privacy in smart contracts by evaluating the contracts off-chain, albeit with the trust assumption of a manager. To avoid the partially trusted manager altogether, a novel approach named zkHawk (IEEE BRAINS ’21) explains how we can evaluate the contracts privately off-chain using a multi-party computation (MPC) protocol instead of trusting said manager. This paper dives deeper into the detailed construction of a variant of the zkHawk protocol titled V-zkHawk using formal proofs to construct the said protocol and model its security in the universal composability (UC) framework (FOCS ’01). The V-zkHawk protocol discussed here does not support immediate closure, i.e., all the parties (n) have to send a message to inform the blockchain that the contract has been executed with corruption allowed for up to t parties, where t<n. In the most quintessential sense, the V-zkHawk is a variant because the outcome of the protocol is similar (i.e., execution of smart contract via an MPC function evaluation) to zkHawk, but we modify key aspects of the protocol, essentially creating a small trade-off (removing immediate closure) to provide UC (stronger) security. The V-zkHawk protocol leverages joint Schnorr signature schemes, encryption schemes, Non-Interactive Zero-Knowledge Proofs (NIZKs), and commitment schemes with Common Reference String (CRS) assumptions, MPC function evaluations, and assumes the existence of asynchronous, authenticated broadcast channels. We achieve malicious security in a dishonest majority setting in the UC framework.

Swaroopa B Reddy

This paper proposes a protocol for Proof of As-sets of a bitcoin exchange using the Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (ZK-SNARK) without revealing either the bitcoin addresses of the exchange or balances associated with those addresses. The proof of assets is a mech-anism to prove the total value of bitcoins the exchange has the authority to spend using its private keys. We construct a privacy-preserving ZK-SNARK proof system to prove the knowledge of the private keys corresponding to the bitcoin assets of an exchange. The ZK-SNARK toolchain helps to convert an NP-Statement for proving the knowledge of the private keys (known to the exchange) into a circuit satisfiability problem. In this protocol, the exchange creates a Pedersen commitment to the value of bitcoins associated with each address without revealing the balance. The simulation results show that the proof generation time, size, and verification time are efficient in practice.

Sam Wouters

In a series of editorials, Analytical Science Advances will highlight emerging scientists that work in the field of Analytical Sciences. For this first editorial, we have invited Dr. Sam Wouters to contribute to this Q/A. We are keen for anyone working in this field to nominate somebody for a Q&A by sending an email to one of the editors and explaining to us why this person should be highlighted. Sam Wouters joined the Department of Chemical Engineering of the Vrije University Brussels (Brussels, Belgium) in 2012 as an MSc student designing and characterizing novel polymeric stationary phases for liquid chromatography. Later he continued as a PhD student in this department working on the miniaturization of chromatographic systems. Sam's motto is ‘working hard and playing hard’, which in fact means he is conducting cutting-edge research with passion and lots of effort, which has led to an outstanding publication record, while outside work he also enjoys his time organizing great parties, making beautiful travels, etc. After his PhD, he joined Agilent Technologies, an instrument manufacturer that is the frontrunner of many analytical technologies. Only recently he moved back to Belgium and joined the R&D team Janssen Pharmaceutical developing novel analytical workflows for the characterization of emerging (bio-)pharmaceuticals. How did you get involved in the field of analytical sciences? I was not a particularly good student at primary school, but when I started in trajectory called Technical Sciences in Belgium when I was 13, things got more interesting I guess. Chemistry, biology, physics: that seemed to make more sense to me. During a 2nd Master, I was combining polymer science with analytical chemistry, studying the synthesis of polymer monoliths to be used as stationary-phase materials in liquid chromatography. This made me divert from material science into analytical science. Drawn to this field, the following 4 years I combined engineering and analytical chemistry, where the passion of Prof. Eeltink for the latter was certainly inspirational. What was the topic of your phd studies? The main idea was to miniaturize an entire ion chromatography (IC) system on a microfluidic platform, with the aim to minimize band-broadening by integrating all components, and eventually realize a portable system. As this is of course a big endeavor, I focused on the key elements, which are the separation and detection. A first important step was to miniaturize the column. A lot of effort went into the in-house manufacturing polymer chips containing a micromachined microfluidic channel. Optimization of the production process and the development of special metal encasing allowed us to establish a pressure rating up to 400 bar, which is more than suitable to do IC, where larger particles are still common use. The microchannels were packed with existing stationary phase materials. Moreover, I developed an approach to create macroporous interconnected polymer (monolithic) stationary phases in situ in the microchannels. Latex coating of the charged monolithic surface, with nanobeads of opposite charge, allowed me to establish the desired ion-exchange retention and capacity. Another key component in IC is a suppressor, which is used to selectively remove ions from the eluent, making the system compatible with conductivity detection. I constructed a miniaturized chemically regenerated membrane suppressor, replacing sodium ions for protons, based on concentration gradient and diffusion. The protons and the sodium hydroxide in the eluent form water. In this way, full conversion of up to 80 mM NaOH to water was achieved applying flow rates as high as 20 µl/min, being compatible with the flow rates for the miniaturized column format. Moreover, a flow through ring-electrode detector cell, yielding sub-ppb level limits of detection, was developed, which was integrated at the outlet of the suppressor chip, located below the separation chip. Proof-of-concept was demonstrated with the analysis of minute amount of samples obtained from a 250-year-old Antarctic ice core. What was your biggest achievement during this time? Despite having a challenging and multidisciplinary topic, I believe we got pretty far in developing components, which actually functioned. Next to successfully conducting my core research, at the same time I managed to contribute to the research of other people, which seemed fruitful with an additional 13 papers as a result. I was also able to personally present my own work during six oral lectures at international conferences, which gave me a great opportunity to connect with my peers and establish scientific collaborations. What advice would you give to recent phd graduates? I had the opportunity to learn from and work together with many very talented PhD students and post-docs during my time, as well as renowned researchers from academia and industry such as Prof. Paul Haddad and Chris Pohl, which really lifted the research to a higher level. This opened a lot of doors, so my advice is to actively try to engage with such people at conferences, although I admit it can be a bit scary to approach ‘gurus’. Despite the above promotion of collaborations, it can also be a pitfall, and in some cases a reason why I see a lot of people struggling to in the end finalize their own PhD. For me it was important to stay focused on getting my own work done and at a certain point in time to prioritize this. Why did you to decide to join industry after your PHD study? For me, halfway through my PhD it was already clear to me I wanted to go into industry to generate more impact and work on solving relevant issues. There's so much interesting research happening at the universities, but often it ends up in a drawer after the graduation. After a short post-doc period in industry, I joined the R&D team of Agilent Technologies in Germany. The idea that I was part of a team developing new technology in close collaboration with some big pharma companies really made this a very fulfilling job. At the same time, it still stayed a bit distant: I only helped provide others the tools to make the difference. I have now recently joined Jansen R&D to fulfil that desire to join a team, which makes the difference by bringing products to the market that will help people. Which skills were lacking for your position in industry and what changes would you suggest for the academic curriculum? Here, it is probably good to start with the quote of J.R. Oppenheimer, with which I opened my PhD booklet: ‘No man should escape our universities without knowing how little he knows’. No course can really prepare you for what is coming, as that will also vary greatly on the directions you will follow. There's no one-fits-all solution there, but I do think when it comes down to doing a PhD, what you will end up learning depends on your own drive and the development opportunities your promotor and you can generate. At a certain level, to many people in industry, the PhD shows a certain minimum qualification, but then the question will be: what else can you do? Knowledge is important but being able to convey knowledge and work together with respect bring you a long way. Can you describe current trends in analytical instrumentation for liquid chromatography? Having joined a research laboratory after my time at an instrument company, it has really sunk in: I often have only 1 shot at getting the data. Luckily vendors are aware of this, and they are following the trend towards more intelligence, with the aim of having more simplicity (but not per se below the hood of the system), and eventually the aim of reaching the goal of ‘zero-failed analysis’. Examples would be automatic checks of the system suitability and performance, automatic start-up, intelligent solvent-level detection, etc. Apart from that there is also the need to solve complex analytical questions, which often involves using complicated setups, such as 2D-LC. I do believe there has been much progress, in making this much more user-friendly (usually by improving the software), and thus more accessible to a broader public. Another example of really creating enabling technology would be the development of online LC, where the aim is to periodically sample directly from a reactor and have feedback loops in place to control the process. In this field of process analytical technologies, it is again software, which is critical to make the difference between being a nice tool, which can occasionally be used by experts, or something which can really be implemented in industry. The scheduling tool provided with the special sampler of the Agilent 1290 Infinity II Online LC allows to monitor processes easily, be it a 20-min small molecule synthesis reaction, or a 3-week fermentation in a bioreactor where multiple-attributes have to be monitored. Which modern technologies are you currently establishing in your laboratory? I was provided the chance to move into the Pharma industry and join the Drug Metabolism and Pharmacokinetics group at Janssen R&D in Belgium, joining the team of Dr. Filip Cuyckens. As a scientist biotransformations the aim is to study the metabolites circulating in the body, to elucidate their structure using high-resolution mass spectrometry and to establish a metabolic pathway. Eventually this contributes to the reports submitted to the Food and Drug Administration (FDA). Part of my job is also renewing existing technology and introducing novel instrumentation to expand on our capabilities. An important tool for our group is a setup capable of injecting very high volumes of sample, for example, 16 ml of plasma (with 50% organic) onto an liquid chromatographic system by making use of a trapping column. This is then transferred to a system with coupled columns where we do online radio-activity detection and mass spectrometry, or fraction collection in 384 well plates with solid scintillation to perform offline counting with long counting times to detect low amount of radioactivity. Given the trend to dose with less radioactivity, the challenge is to inject more or improve detection limits. To better deal with very polar compounds, solvent effects and matrix effects, the capabilities of the setup will be expanded with at-column dilution, which for example works very well with urine. Our group is non-GxP, which means we have a lot of freedom in our experiments. Doing 4D-LC for peak isolation would be a good example. More fundamental research also takes place; our laboratory for example has an ion trap with an infrared laser to study the spectrum of isolated molecules to aid in structure elucidation. An industry first. Where do you see yourself in 10 years? This is the kind of research group and field where there's so much to do and to learn, and it is not impossible to find me in this laboratory still. Of course, the work will not be the same anymore, as there's always the drive to invest in our analytical capabilities, and at the same time the organizations are changing into being more multi-modality, meaning we will be solving more large-molecules-related questions, next to the small-molecules drugs, which still remain important too. Can you say something about your hobbies outside the laboratory? Work-life balance is obviously important to be on top of your game when at work. As such I like to clear the mind while climbing, it is just you and the rock. I'm mostly interested in traditional climbing, which is a discipline where you basically place all your protection yourself; hence you are fully focused and immersed into it. The technical aspects of that style of climbing make it particularly interesting to me. Next to sporty stuff, I like to study and collect WW1 artefacts. The author declares that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Feng Liu, Jiayin QI Jie YANG, Jiayin QI

In recent years, the issue of data privacy has attracted increased attention, and how to achieve effective privacy protection in blockchain is a new research hotspot.In view of the current research status and development trend of blockchain in privacy protection, the privacy protection methods of blockchain in transaction address,prophecy machine and smart contract were explained, and the privacy strategies of blockchain in the protection of basic elements were summarized.Based on high-level literature at home and abroad, two types of blockchain cryptographic protection methods and usage scenarios were analyzed, including special cryptographic primitives and post-quantum cryptography.The advantages and disadvantages of seven cryptographic techniques applicable to current blockchain privacy protection were also reviewed, including attribute-based encryption, special data signature, homomorphic encryption, secure multi-party computation, zero-knowledge proofs, and lattice ciphers.It was concluded that the privacy protection of blockchain applications cannot be achieved without cryptographic technology.Meanwhile, the blockchain privacy protection technologies were analyzed in terms of both basic element protection and cryptographic protection.It was concluded that it was difficult to effectively solve the privacy problem only from the application and contract layers of the blockchain, and various cryptographic technologies should be used to complement each other according to different needs and application scenarios.In addition, according to the current development status of blockchain privacy cryptography, the narrative was developed from blockchain basic element protection and cryptography-based protection.From the perspectives of both endogenous basic element security and exogenous cryptographic privacy security, basic element privacy protection should be studied first, followed by an in-depth analysis of cryptographic protection techniques for blockchain privacy.The strengths and weaknesses and the potential value of the privacy handling aspects of the corresponding safeguards should be measured in terms of the development of technology in conjunction with practical applications, while considering the timeliness of the technology.Finally, an outlook on the future direction of blockchain privacy protection technologies was provided, indicating the issues that need to be addressed in focus.

Jing Zhan, Yongzhen Li, Jiang Zhao, Wei Gao · 6 authors

Abstract Widely adopted blockchain-based fair data exchange protocol have the following problems in multi-party scenario: 1) in multi-buyer v.s. one seller scenario, the negotiation for data availability verification between the buyer and seller reduces transaction throughput greatly. Besides, malicious buyers can launch DoS attacks to prevent the seller from serving others by requiring lots of data availability proofs. 2) in multi-seller v.s. one buyer scenario where the buyer pays for the merged data of all sellers, current protocols treat this as multiple independent transactions, resulting in excessive on-chain costs. Moreover, current protocols neglect that data ownership establishment on-chain may be tampered since the registration info is in plaintext and submitted through the Internet. This paper proposes multi-party non-interactive atomic fair data exchange protocol based on blockchain to solve the above problems, providing data confidentiality, transaction atomic fairness, data intellectual property right protection, and high efficiency. Specifically, we propose transparent zero knowledge proof-based data verification guaranteeing the data confidentiality and transaction fairness. With the proof computed once and used everywhere, transaction throughput is improved greatly and DoS attacks initiated by malicious buyers is prevented. Moreover, the agent representing multi-seller is introduced to reduce on-chain costs. Furthermore, two-stage on-chain ownership registration is proposed to prevent eavesdroppers from impersonating the owner. Finally, we implement a POC (Proof of Concept) of our protocol as the BADE (Blockchain-based multi-party non-interactive Atomic fair Data Exchange). Experiments show that, our throughput within 12 hours is 50 times that of existing solution\cite{ref10}. And in multi-seller scenario, the on-chain gas costs of our protocol is reduced by 19.9\%-30.5\% in different seller/buyer ratios. The fairness of data exchange is also ensured by extra gas costs of dishonest party.

Aisha Zahid Junejo, Manzoor Ahmed Hashmani, Abdullah Alabdulatif, Mehak Maqbool Memon · 6 authors

Preserving anonymity and confidentiality of transactions has become crucial with widespread of the blockchain technology. Despite of the increased efforts for retaining privacy in blockchain networks, invasion attacks are still surfacing. Most of these attacks do not come from outsiders, but from the resident adversarial nodes. Existence of these insider adversaries lead to damaging of an organization’s internal network system and information leakage. Consequently, transaction anonymity and confidentiality are compromised. Hence, adversary detection and filtration play a vital role in protecting networks against unforeseen privacy and security threats. Therefore, in this paper, we propose RZee, a cryptographic and statistical privacy preserving model for adversary detection and filtering in blockchain networks. Firstly, RZee exploits zero-knowledge proofs to cryptographically secure the data. Secondly, based on certain identified conditions, RZee captures node behavior and blacklists malicious nodes to restrict those from injecting harmful data into the chain or viewing transactions as they propagate across the network. This adds an additional layer of protecting transactions from unauthorized and malicious intervention. The proposed framework is evaluated based on various privacy attributes as identified by literature. For this evaluation, 4 different types of experiments have been conducted. Further, the comparison of privacy perseverance of RZee with existing benchmark privacy-preserving frameworks is also done. The results depict that performance and privacy preservation in RZee exceeds the rest with an attribute score of 6.774 and a gain margin of 46.5%.

Daniel Barrack

By using zkSNARKs to prove that values have specific dependent types, it is possible to provably assure compatibility and correctness without revealing sensitive information and extend our trusted computing base well beyond our own system. The approach we developed expands the scope of what non-interactive zero-knowledge proofs can capture to include properties about both the execution and correctness of programs.