Kazım Rıfat Özyılmaz, Mehmet Ug̃ur Dog̃an, Arda Yurdakul
Today, Internet of Things (IoT) devices are the powerhouse of data generation with their ever-increasing numbers and widespread penetration. Similarly, artificial intelligence (AI) and machine learning (ML) solutions are getting integrated to all kinds of services, making products significantly more "smarter". The centerpiece of these technologies is "data". IoT device vendors should be able keep up with the increased throughput and come up with new business models. On the other hand, AI/ML solutions will produce better results if training data is diverse and plentiful. In this paper, we propose a blockchain-based, decentralized and trustless data marketplace where IoT device vendors and AI/ML solution providers may interact and collaborate. By facilitating a transparent data exchange platform, access to consented data will be democratized and the variety of services targeting end-users will increase. Proposed data marketplace is implemented as a smart contract on Ethereum blockchain and Swarm is used as the distributed storage platform.
Iain Stewart, Dragos Ilie, Alexei Zamyatin, Sam M. Werner · 6 authors
Quantum computers are expected to have a dramatic impact on numerous fields due to their anticipated ability to solve classes of mathematical problems much more efficiently than their classical counterparts. This particularly applies to domains involving integer factorization and discrete logarithms, such as public key cryptography. In this paper, we consider the threats a quantum-capable adversary could impose on Bitcoin, which currently uses the Elliptic Curve Digital Signature Algorithm (ECDSA) to sign transactions. We then propose a simple but slow commit-delay-reveal protocol, which allows users to securely move their funds from old (non-quantum-resistant) outputs to those adhering to a quantum-resistant digital signature scheme. The transition protocol functions even if ECDSA has already been compromised. While our scheme requires modifications to the Bitcoin protocol, these can be implemented as a soft fork.
With the Internet of Things (IoT), Things are expected to live in different “domains” and “contexts” during their lifetime. Information generated by and associated with Things should be manageable by multiple, diverse stakeholders accordingly. Moreover, the scope of the information related to Things can range from private and confidential to public and auditable. Identification, security, and interoperability in this vivid environment are expected to be challenging. In this paper we discuss how smart contracts and blockchain technologies create the potential for a viable solution. To this end, we present smart contract-based solutions that improve security and information management, we identify new opportunities and challenges, and we provide security recommendations and guidelines.
Proposed cryptographic protocol with zero-knowledge proof on elliptic curves using one-way hash function, allowing to establish the truth of allegation and does not convey any additional information about the approval. Cryptographic protocols based on zero-knowledge proof allow identification, key exchange and other cryptographic operations to be performed without leakage of sensitive information during the information exchange. The implementation of the cryptographic protocol of the zero-knowledge proof on the basis of the mathematical apparatus of elliptic curves allows to significantly reduce the size of the protocol parameters and increase the cryptographic stability (computational complexity of the hacking problem). The security of cryptosystems on elliptic curves is based on the difficulty of solving the elliptic curve discrete logarithm problem. The completeness and correctness of the protocol is determined in the work, an example of calculation is given, the cryptographic protocol is modeled on the High-Level Protocol Specification Language, the model validation and verification of the protocol are performed. Software verification of the cryptographic protocol was performed using the software modules On the Fly Model Checker and Constraint Logic based Attack Searcher. To validation the cryptographic protocol for resistance to intruder attacks was used the Security Protocol Animator package for Automated Validation of Internet Security Protocols and Applications. The security of the proposed cryptographic protocol is based on the difficulty of solving the elliptic curve discrete logarithm problem and the cryptographic stability of the hash function. To implement the cryptographic protocol, you can use the recommended elliptical curves according to DSTU 4145-2000 and the hash function GOST 34.311-95.
Many companies rely on Cloud infrastructures for their computation, communication and data storage requirements. While Cloud services provide some benefits, e.g., replacing high upfront costs for an IT infrastructure with a pay-as-you-go model, they also introduce serious concerns that are notoriously difficult to address. In essence, Cloud customers are storing data and running computations on infrastructures that they can not control directly. Therefore, when problems arise -- violations of Service Level Agreements, data corruption, data leakage, security breaches -- both customers and Cloud providers face the challenge of agreeing on which party is to be held responsible. In this paper, we review the challenges and requirements for enforcing accountability in Cloud infrastructures, and argue that smart contracts and blockchain technologies might provide a key contribution towards accountable Clouds.
Recent work has demonstrated significant anonymity vulnerabilities in\nBitcoin's networking stack. In particular, the current mechanism for\nbroadcasting Bitcoin transactions allows third-party observers to link\ntransactions to the IP addresses that originated them. This lays the groundwork\nfor low-cost, large-scale deanonymization attacks. In this work, we present\nDandelion++, a first-principles defense against large-scale deanonymization\nattacks with near-optimal information-theoretic guarantees. Dandelion++ builds\nupon a recent proposal called Dandelion that exhibited similar goals. However,\nin this paper, we highlight simplifying assumptions made in Dandelion, and show\nhow they can lead to serious deanonymization attacks when violated. In\ncontrast, Dandelion++ defends against stronger adversaries that are allowed to\ndisobey protocol. Dandelion++ is lightweight, scalable, and completely\ninteroperable with the existing Bitcoin network. We evaluate it through\nexperiments on Bitcoin's mainnet (i.e., the live Bitcoin network) to\ndemonstrate its interoperability and low broadcast latency overhead.\n
Amir Kafshdar Goharshady, Ali Behrouz, Krishnendu Chatteriee
We present a secure approach for maintaining and reporting credit history records on the Blockchain. Our approach removes third-parties such as credit reporting agencies from the lending process and replaces them with smart contracts. This allows customers to interact directly with the lenders or banks while ensuring the integrity, unmalleability and privacy of their credit data. Most importantly, each customer is given full control over complete or selective disclosure of her credit records, eliminating the risk of privacy violations or data breaches such as the one that happened to Equifax in 2017. Moreover, our approach provides strong guarantees for the lenders as well. A lender can check both correctness and completeness of the credit data disclosed to her. This is the first approach that is able to perform all real-world credit reporting tasks without a central authority or changing the financial mechanisms.
Blockchain-based consensus protocols present the opportunity to develop new protocols, due to their novel requirements of open participation and explicit incentivization of participants. To address the first requirement, it is necessary to consider the leader election inherent in consensus protocols, which can be difficult to scale to a large and untrusted set of participants. To address the second, it is important to consider ways to provide incentivization without relying on the resource-intensive proofs-of-work used in Bitcoin. In this paper, we propose a secure leader election protocol, Caucus; we next fit this protocol into a broader blockchain-based consensus protocol, Fantomette, that provides game-theoretic guarantees in addition to traditional blockchain security properties. Fantomette is the first proof-of-stake protocol to give formal game-theoretic proofs of security in the presence of non-rational players.
Mustafa Al-Bassam, Alberto Sonnino, Michał Król, Ioannis Psaras
We present Airtnt, a novel scheme that enables users with CPUs that support Trusted Execution Environments (TEEs) and remote attestation to rent out computing time on secure enclaves to untrusted users. Airtnt makes use of the attestation capabilities of TEEs and smart contracts on distributed ledgers to guarantee the fair exchange of the payment and the result of an execution. Airtnt makes use of off-chain payment channels to allow requesters to pay executing nodes for intermediate "snapshots" of the state of an execution. Effectively, this step-by-step "compute-payment" cycle realises untrusted pay-as-you-go micropayments for computation. Neither the requester nor the executing node can walk away and incur monetary loss to the other party. This also allows requesters to continue executions on other executing nodes if the original executing node becomes unavailable or goes offline.
Freya Sheer Hardwick, Raja Naeem Akram, Konstantinos Markantonakis
At a time when society is in constant transition to keep up with technological advancement, we are seeing traditional paradigms being increasingly challenged. The fundamentals of governance are one such paradigm. As society's values have shifted, so have expectations of government shifted from the traditional model to something commonly referred to as `open governance'. Though a disputed term, we take open governance to mean a concept, which encourages and facilitates openness, accountability, and responsiveness to citizens. For the success of open governance initiatives, there are some technologies, such as the internet, that are crucial. These technologies enable access to both the data and to engagement activities between citizens and government. There are also other technologies, like blockchain and smart contacts, which could be utilised to assist open governance. A sound starting point would be moving from a system where information is tediously released by a government, on an `as they please' basis, to an infrastructure where critical actions are captured with strong integrity, non-repudiation and evidential guarantees. With an added dimension that facilitates these actions record be accessible to public scrutiny in near real-time. One candidate technology for capturing such actions is blockchain. Initially, blockchains were mainly used to facilitate cryptocurrencies as a record of transactions. The notable example being bitcoin. However, in recent years, blockchains utility is being recognised through smart contracts - potentially a vital building block to realising open and transparent government activities. In this paper, we employ the concept of smart contracts to government tendering activities. The proposed scheme is based on smart contracts, enabling a fair, transparent and independently verifiable (auditable) government tendering scheme. The scheme is then implemented on the Ethereum platform to evaluate the performance and financial cost implications, along with an evaluation of the potential security and auditability challenges.
We propose building a new PKC in a ring structure, the classification of rings being an open problem. The difficulty of the scheme is based on retrieving the eigenvalues of endomorphism on a finite type module over a non-commutative ring. It is resistant to a chosen cipher text attack. Working in the fraction ring of a non-commutative ring makes our scheme a zero-knowledge proof of knowledge, result indistinguishable, in the Naor-Yung model. Finally, a dramatic improvement in security is obtained through the drawing with uniform probability of the working ring at high frequency.
Parinya Ekparinya, Vincent Gramoli, Guillaume Jourjon
Recently, several works conjectured the vulnerabilities of mainstream blockchains under several network attacks. All these attacks translate into showing that the assumptions of these blockchains can be violated in theory or under simulation at best. Unfortunately, previous results typically omit both the nature of the network under which the blockchain code runs and whether blockchains are private, consortium or public. In this paper, we study the public Ethereum blockchain as well as a consortium and private blockchains and quantify the feasibility of man-in-the-middle and double spending attacks against them. To this end, we list important properties of the Ethereum public blockchain topology, we deploy VMs with constrained CPU quantum to mimic the top-10 mining pools of Ethereum and we develop full-fledged attacks, that first partition the network through BGP hijacking or ARP spoofing before issuing a Balance Attack to steal coins. Our results demonstrate that attacking Ethereum is remarkably devastating in a consortium or private context as the adversary can multiply her digital assets by 200, 000x in 10 hours through BGP hijacking whereas it would be almost impossible in a public context.
The prevalence of IoT devices makes them an ideal target for attackers. To\nreduce the risk of attacks vendors routinely deliver security updates (patches)\nfor their devices. The delivery of security updates becomes challenging due to\nthe issue of scalability as the number of devices may grow much quicker than\nvendors' distribution systems. Previous studies have suggested a permissionless\nand decentralized blockchain-based network in which nodes can host and deliver\nsecurity updates, thus the addition of new nodes scales out the network.\nHowever, these studies do not provide an incentive for nodes to join the\nnetwork, making it unlikely for nodes to freely contribute their hosting space,\nbandwidth, and computation resources. In this paper, we propose a novel\ndecentralized IoT software update delivery network in which participating nodes\nreferred to as distributors) are compensated by vendors with digital currency\nfor delivering updates to devices. Upon the release of a new security update, a\nvendor will make a commitment to provide digital currency to distributors that\ndeliver the update; the commitment will be made with the use of smart\ncontracts, and hence will be public, binding, and irreversible. The smart\ncontract promises compensation to any distributor that provides\nproof-of-distribution, which is unforgeable proof that a single update was\ndelivered to a single device. A distributor acquires the proof-of-distribution\nby exchanging a security update for a device signature using the Zero-Knowledge\nContingent Payment (ZKCP) trustless data exchange protocol. Eliminating the\nneed for trust between the security update distributor and the security\nconsumer (IoT device) by providing fair compensation, can significantly\nincrease the number of distributors, thus facilitating rapid scale out.\n
As Byzantine Agreement (BA) protocols find application in large-scale decentralized cryptocurrencies, an increasingly important problem is to design BA protocols with improved communication complexity. A few existing works have shown how to achieve subquadratic BA under an {\it adaptive} adversary. Intriguingly, they all make a common relaxation about the adaptivity of the attacker, that is, if an honest node sends a message and then gets corrupted in some round, the adversary {\it cannot erase the message that was already sent} --- henceforth we say that such an adversary cannot perform "after-the-fact removal". By contrast, many (super-)quadratic BA protocols in the literature can tolerate after-the-fact removal. In this paper, we first prove that disallowing after-the-fact removal is necessary for achieving subquadratic-communication BA. Next, we show new subquadratic binary BA constructions (of course, assuming no after-the-fact removal) that achieves near-optimal resilience and expected constant rounds under standard cryptographic assumptions and a public-key infrastructure (PKI) in both synchronous and partially synchronous settings. In comparison, all known subquadratic protocols make additional strong assumptions such as random oracles or the ability of honest nodes to erase secrets from memory, and even with these strong assumptions, no prior work can achieve the above properties. Lastly, we show that some setup assumption is necessary for achieving subquadratic multicast-based BA.
Blockchain is a novel technology that is rising a lot of interest in the industrial and re- search sectors because its properties of decentralisation, immutability and data integrity. Initially, the underlying consensus mechanism has been designed for permissionless block- chain on trustless network model through the proof-of-work, i.e. a mathematical challenge which requires high computational power. This solution suffers of poor performances, hence alternative consensus algorithms as the proof-of-stake have been proposed. Conversely, for permissioned blockchain, where participants are known and authenti- cated, variants of distributed consensus algorithms have been employed. However, most of them comes out without formal expression of security analysis and trust assumptions because the absence of an established knowledge. Therefore the lack of adequate analysis on these algorithms hinders any cautious evaluation of their effectiveness in a real-world setting where systems are deployed over trustless networks, i.e. Internet ...
Fergus Dall, Gabrielle De Micheli, Thomas Eisenbarth, Daniel Genkin · 7 authors
Intel Software Guard Extensions (SGX) allows users to perform secure computation on platforms that run untrusted software. To validate that the computation is correctly initialized and that it executes on trusted hardware, SGX supports attestation providers that can vouch for the user’s computation. Communication with these attestation providers is based on the Extended Privacy ID (EPID) protocol, which not only validates the computation but is also designed to maintain the user’s privacy. In particular, EPID is designed to ensure that the attestation provider is unable to identify the host on which the computation executes. In this work we investigate the security of the Intel implementation of the EPID protocol. We identify an implementation weakness that leaks information via a cache side channel. We show that a malicious attestation provider can use the leaked information to break the unlinkability guarantees of EPID. We analyze the leaked information using a lattice-based approach for solving the hidden number problem, which we adapt to the zero-knowledge proof in the EPID scheme, extending prior attacks on signature schemes.
Edgar González Fernández, Guillermo Morales-Luna, Feliú Sagols Troncoso
Zero-Knowledge Proofs ZKP provide a reliable option to verify that a claim is true without giving detailed information other than the answer. A classical example is provided by the ZKP based in the Graph Isomorphism problem (GI), where a prover must convince the verifier that he knows an isomorphism between two isomorphic graphs without publishing the bijection. We design a novel ZKP exploiting the NP-hard problem of finding the algebraic ideal of a multivariate polynomial set, and consequently resistant to quantum computer attacks. Since this polynomial set is obtained considering instances of GI, we guarantee that the protocol is at least as secure as the GI based protocol.
George Kappos, Haaroon Yousaf, Mary Maller, Sarah Meiklejohn
Among the now numerous alternative cryptocurrencies derived from Bitcoin, Zcash is often touted as the one with the strongest anonymity guarantees, due to its basis in well-regarded cryptographic research. In this paper, we examine the extent to which anonymity is achieved in the deployed version of Zcash. We investigate all facets of anonymity in Zcash's transactions, ranging from its transparent transactions to the interactions with and within its main privacy feature, a shielded pool that acts as the anonymity set for users wishing to spend coins privately. We conclude that while it is possible to use Zcash in a private way, it is also possible to shrink its anonymity set considerably by developing simple heuristics based on identifiable patterns of usage.
Recently, advancements in energy distribution models have fulfilled the needs of microgrids in finding a suitable energy distribution model between producer and consumer without the need of central controlling authority. Most of the energy distribution model deals with energy transactions and losses without considering the security aspects such as information tampering. The transaction data could be accessible online to keep track of the energy distribution between the consumer and producer (e.g., online payment records and supplier profiles). However this data is prone to modification and misuse if a consumer moves from one producer to other. Blockchain is considered to be one solution to allow users to exchange energy related data and keep track of it without exposing it to modification. In this paper, electrical transactions embedded in blockchain are validated using the signatures of multiple producers based on their assigned attributes. These signatures are verified and endorsed by the consumers satisfying those attributes without revealing any information. The public and private keys for these consumers are generated by the producers and endorsement procedure using these keys ensures that these consumers are authorized. This approach does not need any central authority. To resist against collision attacks, producers are given a secret pseudorandom function seed. The comparative analysis shows the efficiency of proposed approach over the existing ones.
Eric Zhang, C Hendrik, Yang Liu, Archit Sharma · 5 authors
In this paper we present the initial design of Minerva consensus protocol for Truechain and other technical details. Currently, it is widely believed in the blockchain community that a public chain cannot simultaneously achieve high performance, decentralization and security. This is true in the case of a Nakamoto chain (low performance) or a delegated proof of stake chain (partially centralized), which are the most popular block chain solutions at time of writing. Our consensus design enjoys the same consistency, liveness, transaction finality and security guarantee, a de-facto with the Hybrid Consensus. We go on to propose the idea of a new virtual machine on top of Ethereum which adds permissioned-chain based transaction processing capabilities in a permissionless setting. We also use the idea of data sharding and speculative transactions, and evaluation of smart contracts in a sharding friendly virtual machine. Finally, we will briefly discuss our fundamentally ASIC resistant mining algorithm, Truehash.
While the Internet of Things (IoT) technology has been widely recognized as the essential part of Smart Cities, it also brings new challenges in terms of privacy and security. Access control (AC) is among the top security concerns, which is critical in resource and information protection over IoT devices. Traditional access control approaches, like Access Control Lists (ACL), Role-based Access Control (RBAC) and Attribute-based Access Control (ABAC), are not able to provide a scalable, manageable and efficient mechanism to meet the requirements of IoT systems. Another weakness in today's AC is the centralized authorization server, which can be the performance bottleneck or the single point of failure. Inspired by the smart contract on top of a blockchain protocol, this paper proposes BlendCAC, which is a decentralized, federated capability-based AC mechanism to enable an effective protection for devices, services and information in large scale IoT systems. A federated capability-based delegation model (FCDM) is introduced to support hierarchical and multi-hop delegation. The mechanism for delegate authorization and revocation is explored. A robust identity-based capability token management strategy is proposed, which takes advantage of the smart contract for registering, propagating and revocating of the access authorization. A proof-of-concept prototype has been implemented on both resources-constrained devices (i.e., Raspberry PI node) and more powerful computing devices (i.e., laptops), and tested on a local private blockchain network. The experimental results demonstrate the feasibility of the BlendCAC to offer a decentralized, scalable, lightweight and fine-grained AC solution for IoT systems.
Muhammad Saad, Aziz Mohaisen, Charles Kamhoua, Kevin Kwait · 5 authors
In this paper, we look at the use of hash-based, one-time signatures in the context of the Blockchain systems and demonstrate how the replacement of currently utilized schemes into a one-time signature can help deter double-spending. Towards this goal, we make the following contributions. 1) We introduce a notion of double- spending deterrence, a form of malleability that does not require pre-authorization from the signer to create a signature on an arbitrary message using two previously signed messages. It is used as a penalty to deter double-spending and disincentivize forgery. 2) We study features of various one-time signature schemes, and we demonstrate their effectiveness in thwarting double-spending. 3) We explore the design space of applying our methodology to the Blockchain system with a clear example and design options to deter double-spending. The results reported in this paper are promising, and open several new directions.
Ahmed E. Kosba, Charalampos Papamanthou, Elaine Shi
Many cloud and cryptocurrency applications rely on verifying the integrity of outsourced computations, in which a verifier can efficiently verify the correctness of a computation made by an untrusted prover. State-of-the-art protocols for verifiable computation require that the computation task be expressed as arithmetic circuits, and the number of multiplication gates in the circuit is the primary metric that determines performance. At the present, a programmer could rely on two approaches for expressing the computation task, either by composing the circuits directly through low-level development tools; or by expressing the computation in a high-level program and rely on compilers to perform the program-to-circuit transformation. The former approach is difficult to use but on the other hand allows an expert programmer to perform custom optimizations that minimize the resulting circuit. In comparison, the latter approach is much more friendly to non-specialist users, but existing compilers often emit suboptimal circuits. We present xJsnark, a programming framework for verifiable computation that aims to achieve the best of both worlds: offering programmability to non-specialist users, and meanwhile automating the task of circuit size minimization through a combination of techniques. Specifically, we present new circuit-friendly algorithms for frequent operations that achieve constant to asymptotic savings over existing ones; various globally aware optimizations for short- and long- integer arithmetic; as well as circuit minimization techniques that allow us to reduce redundant computation over multiple expressions. We illustrate the savings in different applications, and show the framework's applicability in developing large application circuits, such as ZeroCash, while minimizing the circuit size as in low-level implementations.