Blockchain Papers

Craig Calcaterra, Wulf A. Kaal

No abstract is available for this record.

Shuangyu He, Qianhong Wu, Xizhao Luo, Zhi Liang · 8 authors

Effective cryptocurrency key management has become an urgent requirement for modern cryptocurrency. Although a large body of cryptocurrency wallet-management schemes has been proposed, they are mostly constructed for specific application scenarios and often suffer from weak security. In this paper, we propose a more effective, usable, and secure cryptocurrency wallet-management system based on semi-trusted social networks, therein allowing users to collaborate with involved parties to achieve some powerful functions and recovery under certain circumstances. Furthermore, we employ an identity-based hierarchical key-insulated encryption scheme to achieve time-sharing authorization and present a semi-trusted portable social-network-based wallet-management scheme that provides the features of security-enhanced storage, portable login on different devices, no-password authentication, flexible key delegation, and so on. The performance analysis shows that our proposed schemes require minimal additional overhead and have low time delays, making them sufficiently efficient for real-world deployment.

Qun Lin, Hongyang Yan, Zhengan Huang, Wenbin Chen · 6 authors

Identity-based cryptosystems mean that public keys can be directly derived from user identifiers, such as telephone numbers, email addresses, and social insurance number, and so on. So they can simplify key management procedures of certificate-based public key infrastructures and can be used to realize authentication in blockchain. Linearly homomorphic signature schemes allow to perform linear computations on authenticated data. And the correctness of the computation can be publicly verified. Although a series of homomorphic signature schemes have been designed recently, there are few homomorphic signature schemes designed in identity-based cryptography. In this paper, we construct a new ID-based linear homomorphic signature scheme, which avoids the shortcomings of the use of public-key certificates. The scheme is proved secure against existential forgery on adaptively chosen message and ID attack under the random oracle model. The ID-based linearly homomorphic signature schemes can be applied in e-business and cloud computing. Finally, we show how to apply it to realize authentication in blockchain.

Xavier Bultel, Jannik Dreier, Jean‐Guillaume Dumas, Pascal Lafourcade · 10 authors

No abstract is available for this record.

Usman W. Chohan

No abstract is available for this record.

Yi Liu, Xingtong Liu, Chaojing Tang, Jian Wang · 5 authors

Bitcoin combines a peer-to-peer network and cryptographic algorithm to implement a distributed digital currency system, which keeps all transaction history on a public blockchain. Since all transactions recorded on the blockchain are public to everyone, Bitcoin users face a threat of leaking financial privacy. Many analysis and deanonymization approaches have been proposed to link transaction records to real identities. To eliminate this threat, we present an unlinkable coin mixing scheme that allows users to mix their bitcoins without trusting a third party. This mixing scheme employs a primitive known as ring signature with elliptic curve digital signature algorithm (ECDSA) to conceal the transfer of coins between addresses. The mixing server is only able to check whether the output addresses belong to its customers, but it cannot tell which address owned by which customer. Customers do not have to rely on the reputation of a third party to ensure his money will be returned, and his privacy will not be leaked. This scheme needs no modifications on current Bitcoin system and is convenient to deploy by any communities. We implemented a prototype of our scheme and tested it under the Bitcoin core's regtest mode. Security and privacy of our mixing scheme are ensured through the standard ring signature and ECDSA unforgeability.

Carlos Molina-Jiménez, Ellis Solaiman, Ioannis Sfyrakis, Irene C. L. Ng · 5 authors

In this paper we discuss how conventional business contracts can be converted into smart contracts---their electronic equivalents that can be used to systematically monitor and enforce contractual rights, obligations and prohibitions at run time. We explain that emerging blockchain technology is certainly a promising platform for implementing smart contracts but argue that there is a large class of applications, where blockchain is inadequate due to performance, scalability, and consistency requirements, and also due to language expressiveness and cost issues that are hard to solve. We explain that in some situations a centralised approach that does not rely on blockchain is a better alternative due to its simplicity, scalability, and performance. We suggest that in applications where decentralisation and transparency are essential, developers can advantageously combine the two approaches into hybrid solutions where some operations are enforced by enforcers deployed on--blockchains and the rest by enforcers deployed on trusted third parties.

Jason Paul Cruz, Yuichi Kaji, Naoto Yanai

The role-based access control (RBAC) framework is a mechanism that describes the access control principle. As a common interaction, an organization provides a service to a user who owns a certain role that was issued by a different organization. Such trans-organizational RBAC is common in face-toface communication but not in a computer network, because it is difficult to establish both the security that prohibits the malicious impersonation of roles and the flexibility that allows small organizations to participate and users to fully control their own roles. In this paper, we present an RBAC using smart contract (RBAC-SC), a platform that makes use of Ethereum's smart contract technology to realize a trans organizational utilization of roles. Ethereum is an open blockchain platform that is designed to be secure, adaptable, and flexible. It pioneered smart contracts, which are decentralized applications that serve as “autonomous agents”running exactly as programmed and are deployed on a blockchain. The RBAC-SC uses smart contracts and blockchain technology as versatile infrastructures to represent the trust and endorsement relationship that are essential in the RBAC and to realize a challenge-response authentication protocol that verifies a user's ownership of roles. We describe the RBAC-SC framework, which is composed of two main parts, namely, the smart contract and the challenge-response protocol, and present a performance analysis. A prototype of the smart contract is created and deployed on Ethereum's Testnet blockchain, and the source code is publicly available.

Gao Yu-long, Xiu‐Bo Chen, Yuling Chen, Ying Sun · 6 authors

Nowadays, blockchain has become one of the most cutting-edge technologies, which has been widely concerned and researched. However, the quantum computing attack seriously threatens the security of blockchain, and related research is still less. Targeting at this issue, in this paper, we present the definition of post-quantum blockchain (PQB) and propose a secure cryptocurrency scheme based on PQB, which can resist quantum computing attacks. First, we propose a signature scheme based on lattice problem. We use lattice basis delegation algorithm to generate secret keys with selecting a random value, and sign message by preimage sampling algorithm. In addition, we design the first-signature and last-signature in our scheme, which are defined as double-signature. It is used to reduce the correlation between the message and the signature. Second, by combining the proposed signature scheme with blockchain, we construct the PQB and propose this cryptocurrency scheme. Its security can be reduced to the lattice short integer solution (SIS) problem. At last, through our analysis, the proposed cryptocurrency scheme is able to resist the quantum computing attack and its signature satisfies correctness and one-more unforgeability under the lattice SIS assumption. Furthermore, compared with previous signature schemes, the sizes of signature and secret keys are relatively shorter than that of others, which can decrease the computational complexity. These make our cryptocurrency scheme more secure and efficient.

Anastasia Mavridou, Áron Lászka

Blockchain-based distributed computing platforms enable the trusted execution of computation - defined in the form of smart contracts - without trusted agents. Smart contracts are envisioned to have a variety of applications, ranging from financial to IoT asset tracking. Unfortunately, the development of smart contracts has proven to be extremely error prone. In practice, contracts are riddled with security vulnerabilities comprising a critical issue since bugs are by design non-fixable and contracts may handle financial assets of significant value. To facilitate the development of secure smart contracts, we have created the FSolidM framework, which allows developers to define contracts as finite state machines (FSMs) with rigorous and clear semantics. FSolidM provides an easy-to-use graphical editor for specifying FSMs, a code generator for creating Ethereum smart contracts, and a set of plugins that developers may add to their FSMs to enhance security and functionality.

Xuechao Yang, Xun Yi, ‪Surya Nepal‬, Fengling Han

No abstract is available for this record.

Alex Biryukov, Dmitry Khovratovich, Sergei Tikhomirov

Identity is a fundamental concept for the financial industry. In order to comply with regulation, financial institutions must verify the identity of their customers. Identities are currently handled in a centralized way, which diminishes users' control over their personal information and threats their privacy. Blockchain systems, especially those with support for smart contracts (e.g., Ethereum), are expected to serve as a basis of more decentralized systems for digital identity management. We propose a design of a privacy-preserving KYC scheme on top of Ethereum. It would let providers of financial services leverage the potential of blockchain technology to increase effciency of customer onboarding while complying with regulation and protecting users' privacy.

Ilya Grishchenko, Matteo Maffei, Clara Schneidewind

The recent growth of the blockchain technology market puts its main cryptocurrencies in the spotlight. Among them, Ethereum stands out due to its virtual machine (EVM) supporting smart contracts, i.e., distributed programs that control the flow of the digital currency Ether. Being written in a Turing complete language, Ethereum smart contracts allow for expressing a broad spectrum of financial applications. The price for this expressiveness, however, is a significant semantic complexity, which increases the risk of programming errors. Recent attacks exploiting bugs in smart contract implementations call for the design of formal verification techniques for smart contracts. This, however, requires rigorous semantic foundations, a formal characterization of the expected security properties, and dedicated abstraction techniques tailored to the specific EVM semantics. This work will overview the state-of-the-art in smart contract verification, covering formal semantics, security definitions, and verification tools. We will then focus on EtherTrust [ 1 ], a framework for the static analysis of Ethereum smart contracts which includes the first complete small-step semantics of EVM bytecode, the first formal characterization of a large class of security properties for smart contracts, and the first static analysis for EVM bytecode that comes with a proof of soundness.

Sergei Tikhomirov

No abstract is available for this record.

Ilya Grishchenko, Matteo Maffei, Clara Schneidewind

Smart contracts are programs running on cryptocurrency (e.g., Ethereum) blockchains, whose popularity stem from the possibility to perform financial transactions, such as payments and auctions, in a distributed environment without need for any trusted third party. Given their financial nature, bugs or vulnerabilities in these programs may lead to catastrophic consequences, as witnessed by recent attacks. Unfortunately, programming smart contracts is a delicate task that requires strong expertise: Ethereum smart contracts are written in Solidity, a dedicated language resembling JavaScript, and shipped over the blockchain in the EVM bytecode format. In order to rigorously verify the security of smart contracts, it is of paramount importance to formalize their semantics as well as the security properties of interest, in particular at the level of the bytecode being executed. In this paper, we present the first complete small-step semantics of EVM bytecode, which we formalize in the F* proof assistant, obtaining executable code that we successfully validate against the official Ethereum test suite. Furthermore, we formally define for the first time a number of central security properties for smart contracts, such as call integrity, atomicity, and independence from miner controlled parameters. This formalization relies on a combination of hyper- and safety properties. Along this work, we identified various mistakes and imprecisions in existing semantics and verification tools for Ethereum smart contracts, thereby demonstrating once more the importance of rigorous semantic foundations for the design of security verification techniques.

Nicola Atzei, Massimo Bartoletti, Tiziana Cimoli, Stefano Lande · 5 authors

Albeit the primary usage of Bitcoin is to exchange currency, its blockchain and consensus mechanism can also be exploited to securely execute some forms of smart contracts. These are agreements among mutually distrusting parties, which can be automatically enforced without resorting to a trusted intermediary. Over the last few years a variety of smart contracts for Bitcoin have been proposed, both by the academic community and by that of developers. However, the heterogeneity in their treatment, the informal (often incomplete or imprecise) descriptions, and the use of poorly documented Bitcoin features, pose obstacles to the research. In this paper we present a comprehensive survey of smart contracts on Bitcoin, in a uniform framework. Our treatment is based on a new formal specification language for smart contracts, which also helps us to highlight some subtleties in existing informal descriptions, making a step towards automatic verification. We discuss some obstacles to the diffusion of smart contracts on Bitcoin, and we identify the most promising open research challenges.

Rui Guo, Huixian Shi, Qinglan Zhao, Dong Zheng

Electronic Health Records (EHRs) are entirely controlled by hospitals instead of patients, which complicates seeking medical advices from different hospitals. Patients face a critical need to focus on the details of their own healthcare and restore management of their own medical data. The rapid development of blockchain technology promotes population healthcare, including medical records as well as patient-related data. This technology provides patients with comprehensive, immutable records, and access to EHRs free from service providers and treatment websites. In this paper, to guarantee the validity of EHRs encapsulated in blockchain, we present an attribute-based signature scheme with multiple authorities, in which a patient endorses a message according to the attribute while disclosing no information other than the evidence that he has attested to it. Furthermore, there are multiple authorities without a trusted single or central one to generate and distribute public/private keys of the patient, which avoids the escrow problem and conforms to the mode of distributed data storage in the blockchain. By sharing the secret pseudorandom function seeds among authorities, this protocol resists collusion attack out of N from N -1 corrupted authorities. Under the assumption of the computational bilinear Diffie-Hellman, we also formally demonstrate that, in terms of the unforgeability and perfect privacy of the attribute-signer, this attribute-based signature scheme is secure in the random oracle model. The comparison shows the efficiency and properties between the proposed method and methods proposed in other studies.

Bernardo David, Peter Gaži, Aggelos Kiayias, Alexander Russell

No abstract is available for this record.

Shangping Wang, Yinglong Zhang, Yaling Zhang

In traditional cloud storage systems, attribute-based encryption (ABE) is regarded as an important technology for solving the problem of data privacy and fine-grained access control. However, in all ABE schemes, the private key generator has the ability to decrypt all data stored in the cloud server, which may bring serious problems such as key abuse and privacy data leakage. Meanwhile, the traditional cloud storage model runs in a centralized storage manner, so single point of failure may leads to the collapse of system. With the development of blockchain technology, decentralized storage mode has entered the public view. The decentralized storage approach can solve the problem of single point of failure in traditional cloud storage systems and enjoy a number of advantages over centralized storage, such as low price and high throughput. In this paper, we study the data storage and sharing scheme for decentralized storage systems and propose a framework that combines the decentralized storage system interplanetary file system, the Ethereum blockchain, and ABE technology. In this framework, the data owner has the ability to distribute secret key for data users and encrypt shared data by specifying access policy, and the scheme achieves fine-grained access control over data. At the same time, based on smart contract on the Ethereum blockchain, the keyword search function on the cipher text of the decentralized storage systems is implemented, which solves the problem that the cloud server may not return all of the results searched or return wrong results in the traditional cloud storage systems. Finally, we simulated the scheme in the Linux system and the Ethereum official test network Rinkeby, and the experimental results show that our scheme is feasible.

Archana Prashanth Joshi, Meng Han, Yan Wang

Blockchain is gaining traction and can be termed as one of the furthermost prevalent topics nowadays. Although critics question about its scalability, security, and sustainability, it has already transformed many individuals' lifestyle in some areas due to its inordinate influence on industries and businesses. Granting that the features of blockchain technology guarantee more reliable and expedient services, it is important to consider the security and privacy issues and challenges behind the innovative technology. The spectrum of blockchain applications range from financial, healthcare, automobile, risk management, Internet of things (IoT) to public and social services. Several studies focus on utilizing the blockchain data structure in various applications. However, a comprehensive survey on technical and applications perspective has not yet been accomplished. In this paper, we try to conduct a comprehensive survey on the blockchain technology by discussing its structure to different consensus algorithms as well as the challenges and opportunities from the prospective of security and privacy of data in blockchains. Furthermore, we delve into future trends the blockchain technology can adapt in the years to come.Index Terms- Blockchains, Future Trends of Blockchains, Security, Privacy

George Pîrlea, Ilya Sergey

We present the first formalisation of a blockchain-based distributed consensus protocol with a proof of its consistency mechanised in an interactive proof assistant.

Anunay Kulshrestha, Akshay Rampuria, Matthew Denton, Ashwin Sreenivas

We introduce a robust framework that allows for cryptographically secure multiparty computations, such as distributed private value auctions. The security is guaranteed by two-sided authentication of all network connections, homomorphically encrypted bids, and the publication of zero-knowledge proofs of every computation. This also allows a non-participant verifier to verify the result of any such computation using only the information broadcasted on the network by each individual bidder. Building on previous work on such systems, we design and implement an extensible framework that puts the described ideas to practice. Apart from the actual implementation of the framework, our biggest contribution is the level of protection we are able to guarantee from attacks described in previous work. In order to provide guidance to users of the library, we analyze the use of zero knowledge proofs in ensuring the correct behavior of each node in a computation. We also describe the usage of the library to perform a private-value distributed auction, as well as the other challenges in implementing the protocol, such as auction registration and certificate distribution. Finally, we provide performance statistics on our implementation of the auction.

Changsong Yang, Xiaofeng Chen, Yang Xiang

No abstract is available for this record.

Volker Skwarek

Purpose This paper aims to describe a method for Internet-of-Things-devices to achieve industrial grade reliability for information transfer from wireless sensor systems to production systems using blockchain technologies. Design/methodology/approach An increased security and reliability of submitted data within the sensor network could be achieved on an application level. Therefore, a lightweight, high-level communication protocol based on blockchain principles was designed. Findings Blockchain mechanisms can secure the wireless communication of Internet-of-Things-devices in a lightweight and scalable manner. Originality/value The innovation of this research is the successful application of general blockchain mechanisms to increase security of a wireless sensor system without binding to a dedicated blockchain technology.