Blockchain technology adds records to a list using cryptographic links. Therefore, the security of blockchain smart contracts is among the most popular contemporary research topics. To improve the theorem-proving technology in this field, we are developing an extensible hybrid verification tool chain, denoted as FSPVM-E, for Ethereum smart contract verification. This hybrid system extends the proof assistants in Coq, a formal proof-management system. Combining symbolic execution with higher-order theorem-proving, it solves consistency, automation, and reusability problems by standard theorem-proving approaches. This article completes the FSPVM-E by developing its proof engine. FSPVM-E is an extensible definitional interpreter based on our previous work FEther, which is totally developed in the Coq proof assistant. It supports almost all semantics of the Solidity programing language, and simultaneously executes multiple types of symbols. FEther also contains a set of automatic strategies that execute and verify the smart contracts in Coq with a high level of automation. The functional correctness of FEther was verified in Coq. In standard tutorials, the execution efficiency of FEther far exceeded that of the interpreters developed in Coq.
Space situation awareness (SSA) includes tracking of active and inactive resident space objects and assessing the space environment through sensor data collection and processing. To enhance SSA, the dynamic data-driven application systems framework couples online data with offline models to enhance performance by using feedback control, sensor management, and communications reliability. For information management, there is a need for identity authentication and access control (AC) to ensure the integrity of exchanged data as well as to grant authorized entities access right to data and services. Due to decentralization and heterogeneity of SSA systems, it is challenging to build an efficient centralized AC system, which can either be a performance bottleneck or the single point of failure. Inspired by the blockchain and smart contract technology, we introduce blockchain-enabled, decentralized, capability-based access control (BlendCAC), a decentralized authentication, and capability-based AC mechanism to enable effective protection for devices, services, and information in SSA networks. To achieve secure identity authentication, the BlendCAC leverages the blockchain to create virtual trust zones, in which distributed components can identify and update each other in a trustless network environment. A robust identity-based capability token management strategy is proposed, which takes advantage of the smart contract for registration, propagation, and revocation of the access authorization. A proof-of-concept prototype has been implemented on both resources-constrained devices (i.e., Raspberry Pi nodes emulating satellites with sensor observations) and more powerful computing devices (i.e., laptops emulating a ground network) and is tested on a private Ethereum blockchain network. The experimental results demonstrate the feasibility of the BlendCAC scheme to offer a decentralized, scalable, lightweight, and fine-grained AC solution for space system toward SSA.
In the age of Big Data, releasing protected sensitive data at a future point in time is critical for various applications. Such self-emerging data release requires the data to be protected until a prescribed data release time and be automatically released to the recipient at the release time, even if the data sender goes offline. While straight-forward centralized approaches provide a basic solution to the problem, unfortunately they are limited to a single point of trust and involve a single point of control. This paper presents decentralized techniques for supporting self-emerging data using smart contracts in Ethereum blockchain networks. We design a credible and enforceable smart contract for supporting self-emerging data release. The smart contract employs a set of Ethereum peers to jointly follow the proposed timed-release service protocol allowing the participating peers to earn the remuneration paid by the service users. We model the problem as an extensive-form game with imperfect information to protect against possible adversarial attacks including some peers destroying the private data (drop attack) or secretly releasing the private data before the release time (release-ahead attack). We demonstrate the efficacy and attack-resilience of the proposed techniques through rigorous analysis and experimental evaluation. Our implementation and experimental evaluation on the Ethereum official test network demonstrate the low monetary cost and the low time overhead associated with the proposed approach and validate its guaranteed security properties.
Privacy of blockchains has been a matter of discussion since the inception of Bitcoin. Various techniques with a varying degree of privacy protection and complexity have been proposed over the past decade. In this survey, we present a systematic analysis of these proposals in four categories: (i) identity, (ii) transaction, (iii) consensus, and (iv) smart contract privacy. Each of these categories have privacy requirements of its own, and various solutions have been proposed to meet these requirements. Almost every technique in the literature of privacy enhancing technologies have been applied to blockchains: mix networks, zero-knowledge proofs, blind signatures, ring signatures, secure MPC, homomorphic encryption, to name just a few. We analyze each category separately in the paper. We first define the related privacy issues, and then review the proposed solutions. The limitations of each solution and the attacks discovered are also discussed along with the proposals. For each category, we first define the relevant privacy issues, and then review the proposed solutions along with their features and limitations
In December 2017, CryptoKitties, a game on the Ethereum blockchain became an instant success shortly after its launch. It attracted 180,000 users with over $20 million of spend in Ether, and was at one point taking up 12% of all Ethereum transactions.
Technically speaking, CryptoKitties is a smart contract - a piece of code with storage capability that resides on a blockchain. Smart contracts are gaining increasing popularity in recent years. We present a comprehensive review of smart contracts with a focus on existing applications and challenges they face. We have covered the smart contract mechanisms, promising use cases, as well as relevant research work and the open issues.
With a market capitalisation of over USD 205 billion in just under ten years, public distributed ledgers have experienced significant adoption. Apart from novel consensus mechanisms, their success is also accountable to smart contracts. These programs allow distrusting parties to enter agreements that are executed autonomously. However, implementation issues in smart contracts caused severe losses to the users of such contracts. Significant efforts are taken to improve their security by introducing new programming languages and advance verification methods. We provide a survey of those efforts in two parts. First, we introduce several smart contract languages focussing on security features. To that end, we present an overview concerning paradigm, type, instruction set, semantics, and metering. Second, we examine verification tools and methods for smart contract and distributed ledgers. Accordingly, we introduce their verification approach, level of automation, coverage, and supported languages. Last, we present future research directions including formal semantics, verified compilers, and automated verification.
Mustafa Al-Bassam, Alberto Sonnino, Vitalik Buterin
Light clients, also known as Simple Payment Verification (SPV) clients, are nodes which only download a small portion of the data in a blockchain, and use indirect means to verify that a given chain is valid. Typically, instead of validating block data, they assume that the chain favoured by the blockchain's consensus algorithm only contains valid blocks, and that the majority of block producers are honest. By allowing such clients to receive fraud proofs generated by fully validating nodes that show that a block violates the protocol rules, and combining this with probabilistic sampling techniques to verify that all of the data in a block actually is available to be downloaded, we can eliminate the honest-majority assumption, and instead make much weaker assumptions about a minimum number of honest nodes that rebroadcast data. Fraud and data availability proofs are key to enabling on-chain scaling of blockchains (e.g. via sharding or bigger blocks) while maintaining a strong assurance that on-chain data is available and valid. We present, implement, and evaluate a novel fraud and data availability proof system.
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
Sep 22, 2018·2018 IEEE SmartWorld, Ubiquitous Intelligence & Computing, Advanced & Trusted Computing, Scalable Computing & Communications, Cloud & Big Data Computing, Internet of People and Smart City Innovation
Bitcoin, as a decentralized digital currency, has caused extensive research interest. There are many studies based on related protocols on Bitcoin, Bitcoin-based voting protocols also received attention in related literature. In this paper, we propose a Bitcoin-based decentralized privacy-preserving voting mechanism. It is assumed that there are n voters and m candidates. The candidate who obtains t ballots can get x Bitcoins from each voter, namely nx Bitcoins in total. We use a shuffling mechanism to protect voter's voting privacy, at the same time, decentralized threshold signatures were used to guarantee security and assign voting rights. The protocol can achieve correctness, decentralization and privacy-preservings. By contrast with other schemes, our protocol has a smaller number of transactions and can achieve a more functional voting method.
We consider the problem of single-round private information retrieval (PIR) from N replicated databases. We consider the case when B databases are outdated (unsynchronized), or even worse, adversarial (Byzantine), and therefore, can return incorrect answers. In the PIR problem with Byzantine databases (BPIR), a user wishes to retrieve a specific message from a set of M messages with zero-error, irrespective of the actions performed by the Byzantine databases. We consider the T-privacy constraint in this paper, where any T databases can collude, and exchange the queries submitted by the user. We derive the information-theoretic capacity of this problem, which is the maximum number of correct symbols that can be retrieved privately (under the T-privacy constraint) for every symbol of the downloaded data. We determine the exact BPIR capacity to be C = (N -2B)/N·(1-T/(N-2B))/(1-(T/(N - 2B))M), if 2B + T <; N. This capacity expression shows that the effect of Byzantine databases on the retrieval rate is equivalent to removing 2B databases from the system, with a penalty factor of (N - 2B)/N, which signifies that even though the number of databases needed for PIR is effectively N - 2B, the user still needs to access the entire N databases. The result shows that for the unsynchronized PIR problem, if the user does not have any knowledge about the fraction of the messages that are missynchronized, the single-round capacity is the same as the BPIR capacity. Our achievable scheme extends the optimal achievable scheme for the robust PIR (RPIR) problem to correct the errors introduced by the Byzantine databases as opposed to erasures in the RPIR problem. Our converse proof uses the idea of the cut-set bound in the network coding problem against adversarial nodes.
Jonah Brown-Cohen, Arvind Narayanan, Alexandros Psomas, S. Matthew Weinberg
The security of most existing cryptocurrencies is based on a concept called Proof-of-Work, in which users must solve a computationally hard cryptopuzzle to authorize transactions (`one unit of computation, one vote'). This leads to enormous expenditure on hardware and electricity in order to collect the rewards associated with transaction authorization. Proof-of-Stake is an alternative concept that instead selects users to authorize transactions proportional to their wealth (`one coin, one vote'). Some aspects of the two paradigms are the same. For instance, obtaining voting power in Proof-of-Stake has a monetary cost just as in Proof-of-Work: a coin cannot be freely duplicated any more easily than a unit of computation. However some aspects are fundamentally different. In particular, exactly because Proof-of-Stake is wasteless, there is no inherent resource cost to deviating (commonly referred to as the `Nothing-at-Stake' problem). In contrast to prior work, we focus on incentive-driven deviations (any participant will deviate if doing so yields higher revenue) instead of adversarial corruption (an adversary may take over a significant fraction of the network, but the remaining players follow the protocol). The main results of this paper are several formal barriers to designing incentive-compatible proof-of-stake cryptocurrencies (that don't apply to proof-of-work).
It is commonly believed that blockchain is a revolutionary technology for doing business on the Internet. Blockchain is a decentralized, distributed database or ledger of records. It ensures that the records are tamper-proof but publicly readable. Blockchain platforms such as Ethereum [3] and several others execute complex transactions in blocks through user-defined scripts known as smart contracts. Normally, a block of the chain consists of multiple transactions of smart contracts which are added by a miner. To append a correct block into the blockchain, miners execute these transactions of smart contracts sequentially. Later the validators serially re-execute the smart contract transactions of the block. If the validators agree with final state of the blocks as recorded by the miner, then the block is said to be valid and added to the blockchain using a consensus protocol.
BlAsT is an efficient scheme for achieving certification of data continuity through a history attached to a public blockchain. The scheme guarantees the properties of linearity, non-equivocation, time-stamping and transparency. We discuss the implementation of BlAsT over the Bitcoin and the Ethereum blokchains, provide a techno-economic analysis to evaluate the costs related to blockchain adoption, and numerically assess the performance of the proposed architecture in terms of storage and bandwidth requirements. Results show that the above properties can be guaranteed with a small cryptocurrency payment. The proposed scheme can be used for IoT devices under the assumption that the device is able to either perform blockchain validation or delegate it to a trusted node.
The rise of popular cryptocurrencies like Bitcoin and Ethereum has increased the popularity of blockchain technology, the framework these cryptocurrencies are built upon. The security and access control that blockchain technology has provided for cryptocurrencies has peaked the curiosity of other industries, realizing its potential value and future outlook. In this paper, we analyze two types of blockchains, permission-ed and permission-less, and introduce a two-tier blockchain concept utilizing both types for secure data sharing. We provide background on the consensus algorithms used for each blockchain type, Proof-of-Work and Proof-of-Authority. Testing on both Mac OS and Ubuntu Linux-based system environments, preliminary results show that by increasing the number of miners in a Proof-of-Work consensus, there is a correlating increase in the total block count in a permission-less blockchain, where the rate of increase is dependent on the system environment. In the Proof-of-Authority permission-ed blockchain, the block count observed little to no change across both environments.
Yongjun Ren, Yepeng Liu, Sai Ji, Arun Kumar Sangaiah · 5 authors
In this paper, the blockchain technology is utilized to build the first incentive mechanism of nodes as per data storage for wireless sensor networks (WSNs). In our system, the nodes storing the data are rewarded with digital money. The more the data stored by the node, the more the reward it achieves. Moreover, two blockchains are constructed. One is utilized to store data of each node and another is to control the access of data. In addition, our proposal adopts the provable data possession to replace the proof of work (PoW) in original bitcoins to carry out the mining and storage of new data blocks, which greatly reduces the computing power comparing to the PoW mechanism. Furthermore, the preserving hash functions are used to compare the stored data and the new data block. The new data can be stored in the node which is closest to the existing data, and only the different subblocks are stored. Thus, it can greatly save the storage space of network nodes.
Blockchain is a public open ledger that provides data integrity in a distributed manner. It is the underlying technology of cryptocurrencies and an increasing number of related applications, such as smart contracts. The open nature of blockchain together with strong integrity guarantees on the stored data makes it a compelling platform for covert communication. In this paper, we suggest a method of securely embedding covert messages into a blockchain. We formulate a simplified ideal blockchain model based on existing implementations and devise a protocol that enables two parties to covertly communicate through the blockchain following that model. We also formulate a rigorous definition for the security and covertness of such a protocol based on computational indistinguishability. Finally, we show that our method satisfies this definition in the random oracle model for the underlying cryptographic hash function.
Open access
Blockchain Technology Applications and Security
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
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.
In proof-of-stake based consortium blockchain networks, pre-selected miners compete to solve a crypto-puzzle with a successfully mining probability proportional to the amount of their stakes. When the puzzle is solved, the miners are encouraged to take part in mined block propagation for verification to win a transaction fee from the blockchain user. The mined block should be propagated over wired or wireless networks, and be verified as quickly as possible to decrease consensus propagation delay. In this letter, we study incentivizing the consensus propagation considering the tradeoff between the network delay of block propagation process and offered transaction fee from the blockchain user. A Stackelberg game is then formulated to jointly maximize utility of the blockchain user and individual profit of the miners. The blockchain user acting as the leader sets the transaction fee for block verification. The miners acting as the followers decide on the number of recruited verifiers over wired or wireless networks. We apply the backward induction to analyze the existence and uniqueness of the Stackelberg equilibrium. Performance evaluation validates the feasibility and efficiency of the proposed game model in consensus propagation.
Most cryptocurrency systems or systems based on blockchain technology are currently using the elliptic curves digital signature algorithm (ECDSA) on the secp256k1 curve, which is susceptible to backdoors implemented by the curve creator (secp256k1). The paper proposes a multiple elliptic curves digi-tal signature algorithm (MECDSA), which allows not only for setting the number of elliptic curves according to practical security requirements, but also for editing the parameters of each elliptic curve. The performance analy-sis proves that the scheme is secure and efficient, and can avoid any back-doors implemented by curve creators. We suggest that the systems based on blockchain should operate in two elliptic curves considering the contradic-tion between security and efficiency.
We provide enhanced security against insider attacks in services that manage extremely sensitive data. One example is a #MeToo use case where sexual harassment complaints are reported but only revealed when another complaint is filed against the same perpetrator. Such a service places tremendous trust on service operators which our work aims to relieve. To this end we introduce a new autonomous data management concept which transfers responsibility for the sensitive data from administrators to secure and verifiable hardware. The main idea is to manage all data access via a cluster of autonomous computation agents running inside Intel SGX enclaves. These EConfidante agents share a secret data key which is unknown to any external entity, including the data service administrators, thus eliminating many opportunities for data exposure. In this paper we describe a detailed design of the EConfidante system, its flow and how it is managed and implemented. Our #MeToo design also uses an immutable distributed ledger which is built using components from a Blockchain framework. We implemented a proof of concept of our system for the #MeToo use case and analyze its security properties and implementation details.
Aug 1, 2018·2018 17th IEEE International Conference On Trust, Security And Privacy In Computing And Communications/ 12th IEEE International Conference On Big Data Science And Engineering (TrustCom/BigDataSE)
Dimaz Ankaa Wijaya, Joseph K. Liu, Ron Steinfeld, Dongxi Liu
Monero is one of the privacy-preserving cryptocurrencies employing CryptoNote protocol. The privacy features in Monero are provided by cryptographic techniques such as linkable ring signature and one-time public key. Recent studies show that the majority of Monero inputs are traceable prior to mandatory RingCT transaction. After the RingCT was implemented, the problems were mitigated. We propose a novel attack to reduce the anonymity of Monero transactions or even to fully deanonymise the inputs. The proposed protocol can be launched in RingCT protocol and enables multiple attackers to collaborate without trusting each other. The attack scheme can be planted in the existing Monero services without extra fees and without putting the users' money at risk.
Current digital certification revocation systems are insufficient in the application scenario of multiple certification authorities (CAs), and it leads to a lack of mutual trust, access stability, and timeliness of data synchronization between CAs. We propose a decentralized digital certificate revocation system based on consortium blockchain technology with a secret sharing scheme. It can invalidate the digital certificate in special cases to protect the user's information and property security. Based on the characteristics of the decentralized consensus mechanism, consortium blockchain technology is the core technology of the system. The scheme achieves collaborative management of digital certificate revocation lists (CRLs) by multiple CAs, and introduces secret sharing scheme, further safeguarding the reliability of the maintenance process, and then the online certificate status protocol (OCSP) can be developed based on this system. This system is security, effective, and cannot be tampered. Compared with the traditional revocation scheme, it achieves trusted and reliable CRL system above multiple CAs, which can provide new ideas for the way of digital certificate revocation and expand the application range of blockchain technology.
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.