Proof-of-vote is a third generation of the Nakamoto consensus. With proof-of-vote, validators compete for people-votes, using proof-of-suffrage given by proof-of-person, and authorize transactions based on authority delegated by the consensus mechanism, just like proof-of-work or proof-of-stake. This logical conclusion of the Nakamoto consensus allows a “nation” of people to secure their own ledger, the equivalent of representative democracy for distributed ledger technology.
Yasar Khan, Toqeer Ali Syed, Megat Fariz, Fernando Moreira · 7 authors
Abstract An electronic business transaction among untrusted bodies without consulting a mutually trusted party has remained widely accepted problem. Blockchain resolves this problem by introducing peer‐to‐peer network with a consensus algorithm and trusted ledger. Blockchain originally introduced for cryptocurrency that came with proof‐of‐work consensus algorithm. Due to some performance issues, scientists brought concept of permissioned Blockchain. Hyperledger Fabric is a permissioned Blockchain targeting business‐oriented problems for industry. It is designed for efficient transaction execution over Blockchain with pluggable consensus model; however, there is limitation of rapid application development. Hyperledger introduced a new layer called Hyperledger Composer on top of the Fabric layer, which provides an abstract layer to model the business application readily and quickly. Composer provides a smart contract to extend the functionality and flexibility of Fabric layer and provides a way of communication with other systems to meet business requirements. Hyperledger Composer uses role‐based access control (RBAC) model to secure access to its valuable assets. However, RBAC is not enough because many business deals require continuous assets monitoring. Our proposed model, BlockU, covers all possible access control models required by a business. BlockU can monitor assets continuously during transactions and updates attributes accordingly. Moreover, we incorporate hooks in Hyperledger Composer to implement extended permission model that provides extensive permission management capability on an asset. Subsequently, our proposed enhanced access control model is implemented with a minimal change to existing Composer code base and is backward compatible with the current security mechanism.
As a new form of network, the Internet of things (IoT) is becoming more widely used in people’s lives. In this paper, related theoretical research and practical applications of the IoT are explored. The security of the IoT has become a hot research topic. Access controls are methods that control reasonable allocations of data and resources and ensure the security of the IoT. However, most access control systems do not dynamically assign users’ rights. Additionally, with some access control systems, there is a risk of overstepping other user’s authority, and there may exist a central authority that is a single point of failure. Therefore, to solve these problems, this paper proposes a Task-Attribute-Based Access Control scheme for the IoT via blockchain that combines the access control technologies of both the IoT and blockchain. This model, which merges the advantages of task-based access controls and attribute-based access controls, is perfectly integrated with blockchain technology. This model uses hash functions and digital signature algorithms to ensure the authenticity and integrity of the data, and it can dynamically allocate users’ minimum privileges and thus perfectly solves the single point of failure problem. The model is implemented using a Geth client and solidity code, and the simulation results demonstrate the effectiveness of the model.
In this thesis, we present novel methods for verifying, implementing and specifying protocols. In particular, we focus properties modeling data protection and the protection of privacy. In the first part of the thesis, the author introduces protocol verification and presents a model for verification that encompasses so-called Zero-Knowledge (ZK) proofs. These ZK proofs are a cryptographic primitive that is particularly suited for hiding information and hence serves the protection of privacy. The here presented model gives a list of criteria which allows the transfer of verification results from the model to the implementation if the criteria are met by the implementation. In particular, the criteria are less demanding than the ones of previous work regarding ZK proofs. The second part of the thesis contributes to the area of protocol implementations. Hereby, ZK proofs are used in order to improve multi-party computations. The third and last part of the thesis explains a novel approach for specifying data protection policies. Instead of relying on policies, this approach relies on actual legislation. The advantage of relying on legislation is that often a fair balancing is introduced which is typically not contained in regulations or policies.
The main incentives of blockchain technology are distribution and distributed change, consistency, and consensus. Beyond just being a distributed ledger for digital currency, smart contracts add transaction protocols to blockchains to execute terms of a contract in a blockchain network. Inter-blockchain (IBC) protocols define and control exchanges between different blockchains.
The Isabelle Infrastructure framework has been designed to serve security and privacy for IoT architectures by formal specification and stepwise attack analysis and refinement. A major case study of this framework is a distributed health care scenario for data consistency for GDPR compliance. This application led to the development of an abstract system specification of blockchains for IoT infrastructures.
In this paper, we first give a summary of the concept of IBC. We then introduce an instantiation of the Isabelle Infrastructure framework to model blockchains. Based on this we extend this model to instantiate different blockchains and formalize IBC protocols. We prove the concept by defining the generic property of global consistency and prove it in Isabelle.
Verifiable mix nets, and specifically proofs of (correct) shuffle, are a fundamental building block in numerous applications: these zero-knowledge proofs allow the prover to produce a public transcript which can be perused by the verifier to confirm the purported shuffle. They are particularly vital to verifiable electronic voting, where they underpin almost all voting schemes with non-trivial tallying methods. These complicated pieces of cryptography are a prime location for critical errors which might allow undetected modification of the outcome.The best solution to preventing these errors is to machine-check the cryptographic properties of the design and implementation of the mix net. Particularly crucial for the integrity of the outcome is the soundness of the design and implementation of the verifier (software). Unfortunately, several different encryption schemes are used in many different slight variations which makes it infeasible to machine-check every single case individually. However, a particular optimised variant of the Terelius-Wikström mix net is, and has been, widely deployed in elections including national elections in Norway, Estonia and Switzerland, albeit with many slight variations and several different encryption schemes.In this work, we develop the logical theory and formal methods tools to machine-check the design and implementation of all these variants of Terelius-Wikström mix nets, for all the different encryption schemes used; resulting in provably correct mix nets for all these different variations. We do this carefully to ensure that we can extract a formally verified implementation of the verifier (software) which is compatible with existing deployed implementations of the Terelius-Wikström mix net. This gives us provably correct implementations of the verifiers for more than half of the national elections which have used verifiable mix nets.Our implementation of a proof of correct shuffle is the first to be machine-checked to be cryptographically correct and able to verify proof transcripts from national elections. We demonstrate the practicality of our implementation by verifying transcripts produced by the Verificatum mix net system and the CHVote e-voting system from Switzerland.
Cyber-Physical-Social System (CPSS) big data is specified as the global historical data which is usually stored in cloud, the local real-time data which is usually stored in the fog-edge server (FeS) of the mobile terminal devices or sensors, and the social data which is usually stored in the social data server (SdS), moreover adopts a centralized access control mechanism to offer users' access strategy which can easily cause CPSS big data to be tampered with and to be leaked. Therefore, a blockchain-based access control scheme called BacCPSS for CPSS big data is proposed. In BacCPSS, account address of the node in blockchain is used as the identity to access CPSS big data, the access control permission for CPSS big data is redefined and stored in blockchain, and processes of authorization, authorization revocation, access control and audit in BacCPSS are designed, and then a lightweight symmetric encryption algorithm is used to achieve privacy-preserving. Finally, a credible experimental model on EOS and Aliyun cloud is built. Results show that BacCPSS is feasible and effective, and can achieve secure access in CPSS while protecting privacy.
Dara Tith, Joong-Sun Lee, H. Suzuki, W. M. A. B. Wijesundara · 7 authors
OBJECTIVES: Electronic Health Record (EHR) systems are increasingly used as an effective method to share patients' records among different hospitals. However, it is still a challenge to access scattered patient data through multiple EHRs. Our goal is to build a system to access patient records easily among EHRs without relying on a centralized supervisory system. METHODS: We apply consortium blockchain to compose a distributed system using Hyperledger Fabric incorporating existent EHRs. Peer nodes hold the same ledger on which the address of a patient record in an EHR is written. Individual patients are identified by unique certificates issued by a local certificate authorities that collaborate with each other in a channel of the network. To protect a patient's privacy, we use a proxy re-encryption scheme when the data are transferred. We designed and implemented various chaincodes to handle business logic agreed by member organizations of the network. RESULTS: We developed a prototype system to implement our concept and tested its performance including chaincode logic. The results demonstrated that our system can be used by doctors to find patient's records and verify patient's consent on access to the data. Patients also can seamlessly receive their past records from other hospitals. The access log is stored transparently and immutably in the ledger that is used for auditing purpose. CONCLUSIONS: Our system is feasible and flexible with scalability and availability in adapting to existing EHRs for strengthening security and privacy in managing patient records. Our research is expected to provide an effective method to integrate dispersed patient records among medical institutions.
We put forth a new framework for building pairing-based non-interactive zero-knowledge (\(\mathsf {NIZK}\)) arguments for a wide class of algebraic languages, which are an extension of linear languages, containing disjunctions of linear languages and more. Our approach differs from the Groth-Sahai methodology, in that we rely on pairings to compile a \(\varSigma \)-protocol into a \(\mathsf {NIZK}\). Our framework enjoys a number of interesting features:
conceptual simplicity, parameters derive from the \(\varSigma \)-protocol;
proofs as short as resulting from the Fiat-Shamir heuristic applied to the underlying \(\varSigma \)-protocol;
fully adaptive soundness and perfect zero-knowledge in the common random string model with a single random group element as CRS;
yields simple and efficient two-round, public coin, publicly-verifiable perfect witness-indistinguishable (WI) arguments(ZAPs) in the plain model. To our knowledge, this is the first construction of two-rounds statistical witness-indistinguishable arguments from pairing assumptions.
Access control management is an integral part of maintaining the security of an application. Although there has been significant work in the field of cloud access control mechanisms, however, with the advent of Distributed Ledger Technology (DLT), on-chain access control management frameworks hardly exist. Existing access control management mechanisms are tightly coupled with the business logic, resulting in governance issues, non-coherent with existing Identity Management Solutions, low security, and compromised usability. We propose a novel framework to implement dynamic role-based access control for decentralized applications (dApps). The framework allows for managing access control on a dApp, which is completely decoupled from the business application and integrates seamlessly with any dApps. The smart contract architecture allows for the independent management of business logic and execution of access control policies. It also facilitates secure, low cost, and a high degree of flexibility of access control management. The proposed framework promotes decentralized governance of access control policies and efficient smart contract upgrades. We also provide quantitative and qualitative metrics for the efficacy and efficiency of the framework. Any Turing complete smart contract programming language is an excellent fit to implement the framework. We expect this framework to benefit enterprise and non-enterprise dApps and provide greater access control flexibility and effective integration with traditional and state of the art identity management solutions.
Electronic health record (EHR) management systems require the adoption of effective technologies when health information is being exchanged. Current management approaches often face risks that may expose medical record storage solutions to common security attack vectors. However, healthcare-oriented blockchain solutions can provide a decentralized, anonymous and secure EHR handling approach. This paper presents PREHEALTH, a privacy-preserving EHR management solution that uses distributed ledger technology and an Identity Mixer (Idemix). The paper describes a proof-of-concept implementation that uses the Hyperledger Fabric's permissioned blockchain framework. The proposed solution is able to store patient records effectively whilst providing anonymity and unlinkability. Experimental performance evaluation results demonstrate the scheme's efficiency and feasibility for real-world scale deployment.
Access control is one of the most important security concerns, which is critical in resource and information protection over IoT devices. This paper proposes a new scheme that combines attribute-based access control (ABAC) model with blockchain technology and uses smart contracts for access control judgment. This scheme can realize dynamic, distributed and reliable access control in the open IoT environment. The IoT access control system based on this scheme consists of five functional modules. The information registration point registers information for each device that joins the system. Policy enforcement point (PEP) is responsible for managing agent-devices in the system and processing original access requests from access subjects. Policy decision point (PDP) makes access control right decision through smart contracts. Policy administration point (PAP) is used to manage smart contract information. Policy information point (PIP) is used to manage key attribute information of devices used for access control judgment. The scheme also includes three types of smart contracts, one management contract (MC) is used to manage other contracts in the system, one policy decision contract (PDC) is responsible for obtaining attribute information from PIP and making final access control right decision, and a large number of policy contracts (PCs) which composed of a public policy contract (PPC) and a large number of exclusive policy contracts (EPCs). These PCs are used to implement specific attribute-based access control policies. To demonstrate the application of the scheme, we simulated a scenario of access control in a home IoT environment and verified the feasibility of access control decisions using our proposed scheme through three experiments.
Guntur Dharma Putra, Volkan Dedeoglu, Salil S. Kanhere, Raja Jurdak
Heterogeneous and dynamic IoT environments require a lightweight, scalable, and trustworthy access control system for protection from unauthorized access and for automated detection of compromised nodes. Recent proposals in IoT access control systems have incorporated blockchain to overcome inherent issues in conventional access control schemes. However, the dynamic interaction of IoT networks remains uncaptured. Here, we develop a blockchain based Trust and Reputation System (TRS) for IoT access control, which progressively evaluates and calculates the trust and reputation score of each participating node to achieve a self-adaptive and trustworthy access control system. Trust and reputation are explicitly incorporated in the attribute-based access control policy, so that different nodes can be assigned to different access right levels, resulting in dynamic access control policies. We implement our proposed architecture in a private Ethereum blockchain comprised of a Docker container network. We benchmark our solution using various performance metrics to highlight its applicability for IoT contexts.
Muntadher Sallal, Steve Schneider, Matthew Casey, Constantin Cătălin Drăgan · 9 authors
Online voting in the UK generally takes place without verifiability mechanisms, with providers that are trusted to provide ballot privacy and correctness of the result. However, replacing existing systems with verifiable voting systems with brand new algorithms and code presents a business risk to election providers. We present an approach for incremental change: adding a Selene-based verifiability layer to an existing online voting system. Selene is a verifiable e-voting protocol that publishes votes in plaintext alongside tracking numbers that enable voters to confirm that their votes have been captured correctly by the system. This results in a system where even the election authority running the system cannot change the result in an undetectable way. This gives stronger guarantees on the integrity of the election than were previously present. This gives an end-to-end verifiable system we call Verify My Vote (VMV). In addition, we outline how this approach supports further incremental changes towards the deployment of fully trustworthy online voting systems. The paper also describes the use of distributed ledger technology as a component of VMV to manage the verifiability data in a decentralised way for resilience and trust.
Access control has been recognized as a critical issue for preventing unauthorized access to the resources in Internet of Things (IoT) systems. This paper proposes an Attribute-Based Access Control (ABAC) framework for IoT systems by using the emerging Ethereum smart contract technology. The framework consists of one Policy Management Contract (PMC), one Subject Attribute Management Contract (SAMC), one Object Attribute Management Contract (OAMC) and one Access Control Contract (ACC). The PMC, SAMC and OAMC are responsible for storing and managing the ABAC policies, the attributes of subjects (i.e., entities accessing resources) and the attributes of objects (i.e., resources being accessed), respectively. When receiving access requests, the ACC retrieves the subject attributes and object attributes as well as the corresponding policy from the SAMC, OAMC and PMC to perform the access control. Combining the ABAC model and the blockchain technology, this framework is expected to achieve distributed, trustworthy and fine-grained access control for IoT systems. To show the feasibility of the proposed framework, we construct a local private Ethereum blockchain system to implement the four smart contracts and also conduct experiments to test the monetary and time cost.
Yuta Nakamura, Yuanyu Zhang, Masahiro Sasabe, Shoji Kasahara
The large-scale and trustless nature of the Internet of Things (IoT) calls for distributed and trustworthy access control schemes to prevent unauthorized resource access. This paper proposes a Capability-Based Access Control (CapBAC) scheme by applying the emerging Ethereum blockchain technology. This scheme uses Ethereum smart contracts, i.e., executable codes residing in the blockchain, to store and manage the capability tokens, i.e., special data structures that maintain the allowed actions of a user (i.e., subject) on a certain resource (i.e., object). To provide more fine-grained access control and more flexible token management, this scheme defines capability tokens in units of actions, i.e., by dividing a conventional capability token containing multiple actions into multiple ones with each being associated with a certain action. In addition, this scheme uses a delegation graph instead of the delegation tree in existing smart contract-based CapBAC schemes to store the token delegation relationship among the subjects. By storing the tokens and the delegation graph in smart contracts, this scheme allows object owners to verify the ownership and validity of the capability tokens of the subjects. To demonstrate the feasibility of the scheme, we constructed a local Ethereum blockchain network and conducted extensive experiments.
In IoT, a flexible and trustworthy access control framework is of significance to ensure the security of lightweight IoT devices. The conventional centralized access control framework is no longer fit for the open and large-scale IoT environments. In this paper, we propose an attribute-based distributed access control framework (ADAC) for IoT using blockchain technology. The attributes, such as manufacturer and object-specified attribute, are considered in the proposed ADAC for more fine-grained access control in the open and lightweight IoT devices. Particularly, we design a smart contract system, which includes a subject contract (SC), an object contract (OC), an access control contract (ACC) and multiple policy contracts (PCs), to manage and access attributes of IoT devices for distributed and trustworthy access control (DTAC). SC and OC are responsible for managing subject attribute and object attribute information, respectively. PCs are used to manage access control policies. ACC performs authorization judgment by accessing attributes and policies. Finally, a case study is performed to demonstrate the workflow and show that ADAC could achieve fine-grained and flexible access control for IoT.
Access control is a mechanism in computer security that regulates access to the system resources. The current access control systems face many problems, such as the presence of the third-party, inefficiency, and lack of privacy. These problems can be addressed by blockchain, the technology that received major attention in recent years and has many potentials. In this study, we overview the problems of the current access control systems, and then, we explain how blockchain can help to solve them. We also present an overview of access control studies and proposed platforms in the different domains. This paper presents the state of the art and the challenges of blockchain-based access control systems.