Cloud Service Level Agreement (SLA) is challengeable due to lacking a trustworthy platform. This paper presents a witness model to credibly enforce the cloud service level agreement. Through introducing the witness role and using the blockchain based smart contract, we solve the trust issues about who can detect the service violation, how the violation is confirmed and the compensation is guaranteed. In this model, a verifiable consensus sortition algorithm proposed by us is firstly leveraged to select independent witnesses to form a witness committee. They are responsible for a specific service level agreement and get paid by monitoring and detecting service violation. Through carefully designing the witness' payoff function in the agreement, we further leverage game theory to analyze and prove that it is not the witness itself is trustworthy. Instead, the witness has to tell the truth because of its greedy nature, which is the desire to maximize its own revenue. As long as the service violation is confirmed by the witness committee, the compensation is automatically transferred to the customer by the smart contract. Finally, we implement a proof-of-concept prototype with the smart contract of Ethereum blockchain. It demonstrates the feasibility of our model.
Thomas Hepp, Alexander Schoenhals, Christopher Gondek, Béla Gipp
Abstract Currently, timestamps are certified by central timestamping authorities, which have disadvantages of centralization. The concept of the decentralized trusted timestamping (DTT) was developed by Gipp et al. to address these drawbacks. The paper provides insights into the architecture and implementation of a decentralized timestamp service taking the integration of multiple blockchain types into account. Furthermore, the components are introduced and the versatile application scenarios are presented. A future direction of research is the evaluation of blockchain technology and their suitability for timestamping.
Ashar Ahmad, Muhammad Saad, Mostafa Bassiouni, Aziz Mohaisen
Audit logs serve as a critical component in the enterprise business systems that are used for auditing, storing, and tracking changes made to the data. However, audit logs are vulnerable to a series of attacks, which enable adversaries to tamper data and corresponding audit logs. In this paper, we present BlockAudit: a scalable and tamper-proof system that leverages the design properties of audit logs and security guarantees of blockchains to enable secure and trustworthy audit logs. Towards that, we construct the design schema of BlockAudit, and outline its operational procedures. We implement our design on Hyperledger and evaluate its performance in terms of latency, network size, and payload size. Our results show that conventional audit logs can seamlessly transition into BlockAudit to achieve higher security, integrity, and fault tolerance.
Permissioned Blockchain has become quite popular with enterprises forming consortium since it prioritizes trust over privacy. One of the popular platforms for distributed ledger solution,Hyperledger Fabric, requires a transaction to beendorsedor approved by a group of special members known as endorsers before undergoing validation. To endorse a transaction, an endorser mentions its identity along with the signature so that it can be verified later. However, for certain transactions, difference in opinion may exist among endorsers. Disclosing the identity of an endorser may lead to conflict within the consortium. In such cases, an endorsement policy which not only allows an endorser to support a transaction discreetly, but at the same time takes into account the decision of the majority is preferred. Thus we propose an Anonymous Endorsement System which uses a threshold endorsement policy in order to address the issue. To realize at-out-of-nendorsement policy, using any of the existing threshold ring signature for our endorsement system would have violated the privacy of endorsers as either the identity or the secret key of the endorsers get revealed to the party who recombines the signature after collecting each signature share. All these factors motivated us to design a new ring signature scheme, calledFabric’s Constant-Sized Linkable Ring Signature(FCsLRS) withTransaction-Orientedlinkability for hiding identity of the endorsers. We have implemented the signature scheme in Golang and analyzed its security and performance by varying the Rivest-Shamir-Adleman (RSA) modulus size. Feasibility of implementation is supported by experimental analysis. Signature and tag generation time is quite fast and remains constant irrespective of change in message length or endorsement set size for a given RSA modulus value, assuming all the endorsers generates their signature in parallel. Each verifier is required to count and check individual valid ring signature. If the aggregate is above the threshold value, stated by the endorsement policy, then it confirms that the transaction is valid. This increases the verification time depending on the threshold value, but has very little effect on the scalability since generally$t<\!\!\!<n$. Lastly, we also discuss the integration of the scheme on v1.2 Hyperledger Fabric.
The paper suggests a new approach based on blockchain technologies and smart contracts to creation of a distributed system for managing provenance metadata, as well as access rights to data in distributed storages, which is fault-tolerant, safe and secure from the point of view of preservation of metadata records from accidental or intentional distortions. The implementation of the proposed approach is based on the permissioned blockchains and on the Hyperledger Fabric blockchain platform in conjunction with Hyperledger Composer.
Oct 26, 2018·Proceedings of the 2018 26th ACM Joint Meeting on European Software Engineering Conference and Symposium on the Foundations of Software Engineering
Daejun Park, Yi Zhang, Manasvi Saxena, Philip Daian · 5 authors
In this paper, we present a formal verification tool for the Ethereum Virtual Machine (EVM) bytecode. To precisely reason about all possible behaviors of the EVM bytecode, we adopted KEVM, a complete formal semantics of the EVM, and instantiated the K-framework's reachability logic theorem prover to generate a correct-by-construction deductive verifier for the EVM. We further optimized the verifier by introducing EVM-specific abstractions and lemmas to improve its scalability. Our EVM verifier has been used to verify various high-profile smart contracts including the ERC20 token, Ethereum Casper, and DappHub MakerDAO contracts.
Ethereum Private Sidechains are permissioned Ethereum blockchains which allow authorised participants to interact privately using Smart Contracts. Permissioned blockchains are appropriate for use in scenarios in which the list of blockchain participants and the code and state of contracts on the blockchain must be kept secret. Ethereum Registration Authorities are a system of Smart Contracts which can be used to resolve bootstrap information based on domain names to allow Ethereum Private Sidechains to be established between parties which have not previously interacted. This paper presents the architecture, design, and gas usage of a reference implementation for the Ethereum Registration Authority system. It analyses the security properties of the system and shows that it is secure, decentralized, and censorship resistant. The reference implementation gas usage is analysed and shown to be independent of the length of domain name and number of entries in the Smart Contracts.
Rosario Gennaro, Michele Minelli, Anca Nitulescu, Michele Orrù
Zero-knowledge SNARKs (zk-SNARKs) are non-interactive proof systems with short and efficiently verifiable proofs. They elegantly resolve the juxtaposition of individual privacy and public trust, by providing an efficient way of demonstrating knowledge of secret information without actually revealing it. To this day, zk-SNARKs are being used for delegating computation, electronic cryptocurrencies, and anonymous credentials. However, all current SNARKs implementations rely on pre-quantum assumptions and, for this reason, are not expected to withstand cryptanalitic efforts over the next few decades. In this work, we introduce the first designated-verifier zk-SNARK based on lattice assumptions, which are believed to be post-quantum secure. We provide a generalization in the spirit of Gennaro et al. (Eurocrypt'13) to the SNARK of Danezis et al. (Asiacrypt'14) that is based on Square Span Programs (SSPs) and relies on weaker computational assumptions. We focus on designated-verifier proofs and propose a protocol in which a proof consists of just 5 LWE encodings. We provide a concrete choice of parameters as well as extensive benchmarks on a C implementation, showing that our construction is practically instantiable.
Mustafa Al-Bassam, Alberto Sonnino, Vitalik Buterin
Light clients, also known as Simple Payment Verification (SPV) clients, are\nnodes which only download a small portion of the data in a blockchain, and use\nindirect means to verify that a given chain is valid. Typically, instead of\nvalidating block data, they assume that the chain favoured by the blockchain's\nconsensus algorithm only contains valid blocks, and that the majority of block\nproducers are honest. By allowing such clients to receive fraud proofs\ngenerated by fully validating nodes that show that a block violates the\nprotocol rules, and combining this with probabilistic sampling techniques to\nverify that all of the data in a block actually is available to be downloaded,\nwe can eliminate the honest-majority assumption, and instead make much weaker\nassumptions about a minimum number of honest nodes that rebroadcast data. Fraud\nand data availability proofs are key to enabling on-chain scaling of\nblockchains (e.g. via sharding or bigger blocks) while maintaining a strong\nassurance that on-chain data is available and valid. We present, implement, and\nevaluate a novel fraud and data availability proof system.\n
Guicang Peng, Songpu Ai, Li Zhang, Chunming Rong · 5 authors
Equipment management is gradually becoming more decentralized, and in many cases, the equipment owner, operator, maintainer and inspector are not the same legal entity. This slows down equipment data transmission between stakeholders and reduces business and technical process automation. In this paper we dis-cussed the use of a distributed ledger concept and propose to use private block-chain together with smart contract to resolve these challenges and to create a more automated and surveillance-free equipment lifecycle management process.
Smart contracts are a new paradigm that emerged with the rise of the blockchain technology. They allow untrusting parties to arrange agreements. These agreements are encoded as a programming language code and deployed on a blockchain platform, where all participants execute them and maintain their state. Smart contracts are promising since they are automated and decentralized, thus limiting the involvement of third trusted parties, and can contain monetary transfers. Due to these features, many people believe that smart contracts will revolutionize the way we think of distributed applications, information sharing, financial services, and infrastructures. To release the potential of smart contracts, it is necessary to connect the contracts with the outside world, such that they can understand and use information from other infrastructures. For instance, smart contracts would greatly benefit when they have access to web content. However, there are many challenges associated with realizing such a system, and despite the existence of many proposals, no solution is secure, provides easily-parsable data, introduces small overheads, and is easy to deploy. In this paper we propose PDFS, a practical system for data feeds that combines the advantages of the previous schemes and introduces new functionalities. PDFS extends content providers by including new features for data transparency and consistency validations. This combination provides multiple benefits like content which is easy to parse and efficient authenticity verification without breaking natural trust chains. PDFS keeps content providers auditable, mitigates their malicious activities (like data modification or censorship), and allows them to create a new business model. We show how PDFS is integrated with existing web services, report on a PDFS implementation and present results from conducted case studies and experiments.
Keltoum Bendiab, Nicholas Kolokotronis, Stavros Shiaeles, Samia Boucherkha
Secure and reliable management of identities has become one of the greatest challenges facing cloud computing today, mainly due to the huge number of new cloud-based applications generated by this model, which means more user accounts, passwords, and personal information to provision, monitor, and secure. Currently, identity federation is the most useful solution to overcome the aforementioned issues and simplify the user experience by allowing efficient authentication mechanisms and use of identity information from data distributed across multiple domains. However, this approach creates considerable complexity in managing trust relationships for both the cloud service providers and their clients. Poor management of trust in federated identity management systems brings with it many security, privacy and interoperability issues, which contributes to the reluctance of organizations to move their critical identity data to the cloud. In this paper, we aim to address these issues by introducing a novel trust and identity management model based on the Blockchain for cloud identity management with security and privacy improvements.
Petr Novotny, Qi Zhang, Richard Hull, Salman Baset · 8 authors
Academic publishing is continuously evolving with the gradual adoption of new technologies. Blockchain is a new technology that promises to change how individuals and organizations interact across various boundaries. The adoption of blockchains is beginning to transform diverse industries such as finance, supply chain, international trade, as well as energy and resource management and many others. Through trust, data immutability, decentralized distribution of data, and facilitation of collaboration without the need for centralized management and authority, blockchains have the potential to transform the academic publishing domain and to address some of the current problems such as productivity and reputation management, predatory publishing, transparent peer-review processes and many others. In this paper, we outline the technologies available in the domain of permissioned blockchains with focus on Hyperledger Fabric and discuss how they can be leveraged in the domain of academic publishing.
Interest in green energy has increased worldwide. Therefore, smart grid projects to form a more efficient and eco-friendly intelligent grid by combining information technology (IT) technology with the existing grid are actively being conducted. In Korea, a national-level smart grid project road map has been confirmed, and an action plan has been prepared. Despite such actions, there may appear various threat scenarios in the application of the IT to the grid as a reverse function. Security technology is a measure to respond to such threats effectively. The security technology of a smart grid is an important factor that is directly related to the success or failure of the smart grid project. A smart grid is a new type of next-generation grid born of the fusion with IT. If the smart grid, the backbone of the power supply, is damaged by a cyberattack, it may cause huge damage, such as a nationwide power outage. In fact, there is an increasing cyberattack threat, and the cyber security threat to the smart grid is not insignificant. Furthermore, the legal system related to information protection is also important in order to support it systematically. In this paper, the necessity of the smart grid is examined, and the industry’s initiative toward the smart grid security threat and threat response is examined. In this paper, we also suggest a security plan of applying Rainbowchain, the Blockchain technology, to the smart grid and energy exchange. We propose achieving superior performance and security functions by using Rainbowchain, which contains seven authentication techniques among existing Blockchain technologies, and propose the ecosystem and architecture necessary for its application.
Most languages are given an informal semantics until they are implemented, so the formal semantics comes later. Consequently, there are usually inconsistencies among the informal semantics, the implementation, and the formal semantics. IELE is an LLVM-like language for the blockchain that was specified formally and its implementation, a virtual machine, generated from the formal specification. Moreover, its design was based on problems observed formalizing the semantics of the Ethereum Virtual Machine (EVM) and from formally specifying and verifying EVM programs (also called “smart contracts”), so even the design decisions made for IELE are based on formal specifications. A compiler from Solidity, the predominant high-level language for smart contracts, to IELE has also been implemented, so Ethereum contracts can now also be executed on IELE. The virtual machine automatically generated from the semantics of IELE is shown to be competitive in terms of performance with the state of the art and hence can stand as the de facto implementation of the language in a production setting. Indeed, IOHK, a major blockchain company, is currently experimenting with the IELE VM in order to deploy it as its computational layer in a few months. This makes IELE the first practical language that is designed and implemented as a formal specification. It took only 10 man-months to develop IELE, which demonstrates that the programming language semantics field has reached a level of maturity that makes it appealing over the traditional, adhoc approach even for pragmatic reasons.
Raziel combines secure multi-party computation and proof-carrying code to provide privacy, correctness and verifiability guarantees for smart contracts on blockchains. Effectively solving DAO and Gyges attacks, this paper describes an implementation and presents examples to demonstrate its practical viability (e.g., private and verifiable crowdfundings and investment funds). Additionally, we show how to use Zero-Knowledge Proofs of Proofs (i.e., Proof-Carrying Code certificates) to prove the validity of smart contracts to third parties before their execution without revealing anything else. Finally, we show how miners could get rewarded for generating pre-processing data for secure multi-party computation.
Blockchain technology is a revolution started as a new economy with an alternative currency namely Bitcoin. Besides the economical aspect, the technological capabilities of Blockchain such as distributed computing, record keeping, irrecoverability of transactions, reliability and etc., are harness
The Distributed nature of Bitcoin introduces security issues that necessitate security-specific enhancements in Bitcoin protocol. Therefore, proposing a method of incorporating criteria check and verification process for miners to participate in the mining process and join the mining pool respective
Many studies have been done to improve the performance of centrally controlled business processes and enhance the integration between different parties of these collaborations. However, the most serious issues of collaborative business processes remained unsolved in these studies - lack of trust and divided data on various confidential ledgers. Blockchain technology has enormous potential to become a new substantial integration method for untrusted collaborative businesses. Using the governing consensus mechanism, blockchain eliminates the necessity of the trusted third party. It provides a distributed shared ledger which facilitates the job of the process monitoring for the parties. The smart contract, as a crucial tool, is used to define the guaranteed autonomous programs. In addition, the privacy of the data can be ensured by using a permissioned blockchain that handles the access control because, in this way, only verifiable participants can have access to the state of the business process and its related information. In this study, the applicability of execution of a real-world untrusted business process on the permissioned blockchain is investigated. Moreover, we determine the advantages of using the permissioned access-controller blockchain as the infrastructure for the collaborative business processes, through implementing the process of Order Processing on the Hyperledger Fabric blockchain platform.
Using blockchain as a decentralized backend infrastructure has been attracting many startups entrepreneurs' and developers' attention. Blockchain records transactions permanently and protects them from undesirable tampering. It provides a reliable tamper-proof database which can be considered as a trustable resource for tracking previous system's state. In this paper, we present our access control application based on Hyperledger Fabric Blockchain and Hyperledger Composer to control access to physical places. The system components and modular architecture are illustrated, and we have extracted metadata include historian transactions' details arising from our demo test. Finally, the performance metrics and resources consumption are provided using Hyperledger Caliper, a benchmark framework for measuring Hyperledger blockchains performance.
Sara Rouhani, Luke Butterworth, Adam D. Simmons, Darryl G. Humphery · 5 authors
The set of distributed ledger architectures known as blockchain is best known for cryptocurrency applications such as Bitcoin and Ethereum. These permissionless block chains are showing the potential to be disruptive to the financial services industry. Their broader adoption is likely to be limited by the maximum block size, the cost of the Proof of Work consensus mechanism, and the increasing size of any given chain overwhelming most of the participating nodes. These factors have led to many cryptocurrency blockchains to become centralized in the nodes with enough computing power and storage to be a dominant miner and validator. Permissioned chains operate in trusted environments and can, therefore, avoid the computationally expensive consensus mechanisms. Permissioned chains are still susceptible to asset storage demands and non-standard user interfaces that will impede their adoption. This paper describes an approach to addressing these limitations: permissioned blockchain that uses off-chain storage of the data assets and this is accessed through a standard browser and mobile app. The implementation in the Hyperledger framework is described as is an example use of patient-centered health data management.
Uchi Ugobame Uchibeke, Kevin A. Schneider, Sara Hosseinzadeh Kassani, Ralph Deters
In recent years, the advancement in modern technologies has not only resulted in an explosion of huge data sets being captured and recorded in different fields, but also given rise to concerns in the security and protection of data during storage, transmission, processing, and access. The blockchain is a distributed ledger that records transactions in a secure, flexible, verifiable and permanent way. Transactions in a blockchain can be an exchange of an asset, the execution of the terms of a smart contract, or an update to a record. In this paper, we have developed a blockchain access control ecosystem that gives asset owners the sovereign right to effectively manage access control of large data sets and protect against data breaches. The Linux Foundation's Hyperledger Fabric blockchain is used to run the business network while the Hyperledger composer modeling tool is used to implement the smart contracts or transaction processing functions that run on the blockchain network.
Thomas Locher, Sebastian Obermeier, Yvonne-Anne Pignolet
The functionality that distributed ledger technology provides, i.e., an immutable and fraud-resistant registry with validation and verification mechanisms, has traditionally been implemented with a trusted third party. Due to the distributed nature of ledger technology, there is a strong recent trend towards using ledgers to implement novel decentralized applications for a wide range of use cases, e.g., in the financial sector and sharing economy. While there can be several arguments for the use of a ledger, the key question is whether it can fully replace any single trusted party in the system as otherwise a (potentially simpler) solution can be built around the trusted party. In this paper, we introduce an abstract view on ledger use cases and present two fundamental criteria that must be met for any use case to be implemented using a ledger-based approach without having to rely on any particular party in the system. Moreover, we evaluate several ledger use cases that have recently received considerable attention according to these criteria, revealing that often participants need to trust each other despite using a distributed ledger. Consequently, the potential of using a ledger as a replacement for a trusted party is limited for these use cases.
A blockchain is a datastructure that is an append-only chain of blocks. Each\nblock contains a set of transaction and has a cryptographic link back to\nits predecessor. The cryptographic link serves to protect the integrity of\nthe blockchain. A key property of blockchain systems is that it allows mu-\ntually distrusting entities to reach consensus over a unique order in which\ntransactions are appended. The most common usage of blockchains is in\ncryptocurrencies such as Bitcoin.\nIn this thesis we use blockchain technology to design a scalable architec-\nture for a storage system that can provide strong data integrity and ensure the\npermanent availability of the data. We study recent literature in blockchain\nand cryptography to identify the desired characteristics of such a system. In\ncomparison to similar systems, we are able to gain increased performance by\ndesigning ours around a permissioned blockchain, allowing only a predefined\nset of nodes to write to the ledger. A prototype of the system is built on top\nof existing open-source software. An experimental evaluation using different\nquorum sizes of the prototype is also presented.