In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

PORs: Proofs of Retrievability for Large Files

Blockchain Technology in Healthcare: A Systematic Review.

Modern healthcare systems are characterized as being highly complex and costly. However, this can be reduced through improved health record management, utilization of insurance agencies, and blockchain technology. Blockchain was first introduced to provide distributed records of money-related exchanges that were not dependent on centralized authorities or financial institutions. Breakthroughs in blockchain technology have led to improved transactions involving medical records, insurance billing, and smart contracts, enabling permanent access to and security of data, as well as providing a distributed database of transactions. One significant advantage of using blockchain technology in the healthcare industry is that it can reform the interoperability of healthcare databases, providing increased access to patient medical records, device tracking, prescription databases, and hospital assets, including the complete life cycle of a device within the blockchain infrastructure. Access to patients’ medical histories is essential to correctly prescribe medication, with blockchain being able to dramatically enhance the healthcare services framework. In this paper, several solutions for improving current limitations in healthcare systems using blockchain technology are explored, including frameworks and tools to measure the performance of such systems, e.g., Hyperledger Fabric, Composer, Docker Container, Hyperledger Caliper, and the Wireshark capture engine. Further, this paper proposes an Access Control Policy Algorithm for improving data accessibility between healthcare providers, assisting in the simulation of environments to implement the Hyperledger-based eletronic healthcare record (EHR) sharing system that uses the concept of a chaincode. Performance metrics in blockchain networks, such as latency, throughput, Round Trip Time (RTT). have also been optimized for achieving enhanced results. Compared to traditional EHR systems, which use client-server architecture, the proposed system uses blockchain for improving efficiency and security.

Blockchain-based electronic healthcare record system for healthcare 4.0 applications

Due to the proliferation of ICT during the last few decades, there is an exponential increase in the usage of various smart applications such as smart farming, smart healthcare, supply-chain & logistics, business, tourism and hospitality, energy management etc. However, for all the aforementioned applications, security and privacy are major concerns keeping in view of the usage of the open channel, i.e., Internet for data transfer. Although many security solutions and standards have been proposed over the years to enhance the security levels of aforementioned smart applications, but the existing solutions are either based upon the centralized architecture (having single point of failure) or having high computation and communication costs. Moreover, most of the existing security solutions have focussed only on few aspects and fail to address scalability, robustness, data storage, network latency, auditability, immutability, and traceability. To handle the aforementioned issues, blockchain technology can be one of the solutions. Motivated from these facts, in this paper, we present a systematic review of various blockchain-based solutions and their applicability in various Industry 4.0-based applications. Our contributions in this paper are in four fold. Firstly, we explored the current state-of-the-art solutions in the blockchain technology for the smart applications. Then, we illustrated the reference architecture used for the blockchain applicability in various Industry 4.0 applications. Then, merits and demerits of the traditional security solutions are also discussed in comparison to their countermeasures. Finally, we provided a comparison of existing blockchain-based security solutions using various parameters to provide deep insights to the readers about its applicability in various applications.

Blockchain for Industry 4.0: A Comprehensive Review

With the development of electronic information technology, electronic medical records (EMRs) have been a common way to store the patients' data in hospitals. They are stored in different hospitals' databases, even for the same patient. Therefore, it is difficult to construct a summarized EMR for one patient from multiple hospital databases due to the security and privacy concerns. Meanwhile, current EMRs systems lack a standard data management and sharing policy, making it difficult for pharmaceutical scientists to develop precise medicines based on data obtained under different policies. To solve the above problems, we proposed a blockchain-based information management system, MedBlock, to handle patients' information. In this scheme, the distributed ledger of MedBlock allows the efficient EMRs access and EMRs retrieval. The improved consensus mechanism achieves consensus of EMRs without large energy consumption and network congestion. In addition, MedBlock also exhibits high information security combining the customized access control protocols and symmetric cryptography. MedBlock can play an important role in the sensitive medical information sharing.

MedBlock: Efficient and Secure Medical Data Sharing Via Blockchain

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.

Secure Attribute-Based Signature Scheme With Multiple Authorities for Blockchain in Electronic Health Records Systems

The vehicular ad-hoc networks (VANETs) is one of the most promising application in the communications of smart vehicles and the smart transportation systems. However, authentication and privacy of users are still two vital issues in VANETs. It is crucial to prevent internal vehicles from broadcasting the forged messages while preserving the privacy of vehicles against the tracking attack. Moreover, in the traditional mode, the transactional data storage provides no distributed and decentralized security, so that the third party initiates the dishonest behaviors possibly. In this paper, based on blockchain technique, we propose a traceable and decentralized the Internet of Vehicle system framework for communication among smart vehicles by employing of a secure access authentication scheme between vehicles and RoadSide Units (RSUs). On the one hand, this scheme allows that vehicles employ pseudonyms for Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communications anonymously in the non-fully trusted environment. On the other hand, the transparency of vehicles in authentication and announcement is preformed efficiently by the blockchain technology. In addition, the transaction information is tamper-resistant that provides the distributed and decentralized property for the different cloud servers. With the help of Certificate Authority (CA) and the RoadSide Units (RSUs), our proposal achieves the conditional privacy to trace the real identity of the malicious vehicle in the anonymous announcements as well. Finally, through the theoretical analysis and simulations, our scheme is able to construct a secure and decentralized system framework of VANETs with accountability and privacy preservation.

/pdf/a-traceable-blockchain-based-access-authentication-system-py0zhq9uwd.pdf

A Traceable Blockchain-Based Access Authentication System With Privacy Preservation in VANETs

Telemedicine offers a medical-on-demand (MoD) service from a distance. This technology is designed to overcome distance barriers and improve the process of accessing medical services in distant rural communities. With the development of cloud computing, the MoD services in the telemedicine system are provided by the Cloud Service Provider (CSP). This CSP connects the patient and the medical staff in different places with both convenience and fidelity. Meanwhile, the outsourcing healthcare data on public cloud platforms bring some new challenges on the security. Although attribute-based encryption (ABE) algorithm realizes flexible and fine-grained access control, a large number of patients subscribe or unsubscribe the different medical services frequently in the cloud, which takes a huge cost for membership management. In this paper, an ABE scheme is presented to achieve the dynamic authentication and authorization with higher flexibility and efficiency for the MoD services in telemedicine system. On the one hand, when the patient alters his ordered service, it requires no updating on the parameters for those whose statuses remain unchanged. We construct an independent-update key policy ABE scheme in the distributed telemedicine system that aims to updates patient's keys separately, and there are multiple authorities to manage this system altogether which is more similar to the real situation. On the other hand, by using blockchain and distributed database technologies, the private healthcare data stored in public cloud is protected in integrity, which avoids the misdiagnosis accident from the inaccurate electronic health records distorted by a malicious user or authority from the inner cloud. Finally, we analyze the collusion attack in multiple authorities and formally prove the security of this protocol in a standard model. After comparing and simulating, the results of this work show a better performance.

Flexible and Efficient Blockchain-Based ABE Scheme With Multi-Authority for Medical on Demand in Telemedicine System

As an important method of making democratic decisions, voting has always been a topic of social concern. Compared with the traditional, e-voting is widely used in various decision scenarios because of the convenience, easy to participate and low cost. However, the proposed e-voting protocols are at the risk of excessive authority and tampered information, which makes it impossible to achieve true fairness and transparency in e-voting. By combining the blockchain technology, it enables to solve these problems with the decentralization and tamper-resistant features. Moreover, the misoperations of the voters will also affect this fairness, such as voting for non-candidates, abstention or repeated voting. Therefore, to ensure the efficiency of the voting process and maintain the fairness of the voting environment, it is important to append the function of audit in e-voting protocol. This paper proposes an e-voting protocol based on blockchain, which provides transparency in the process of voting. At the same time, this scheme has the ability to audit voters operating incorrectly and resist quantum attacks by adopting the certificateless and code-based cryptography. After performance analysis, our scheme is suitable for the small-scale election and has some advantages in security and efficiency when the number of voters is small.

/pdf/an-anti-quantum-e-voting-protocol-in-blockchain-with-audit-grh6qlf9d9.pdf

An Anti-Quantum E-Voting Protocol in Blockchain With Audit Function

Since the ancient times, there exist all kinds of criminals in the world. In order to punish them, most authorities usually encourage the people to provide the evidence of a crime. To avoid the revenges from the criminals, it is necessary to study the anonymous reporting scheme with anonymous rewarding. In this paper, for the first time, we propose the novel concept of blockchain-based anonymous reporting scheme with anonymous rewarding (BB2AR). Our BB2AR scheme solves the open problem: how to realize the anonymous reporting and the anonymous rewarding simultaneously? First, we formalize the system model, definition, and security model of BB2AR. Second, we propose a concrete BB2AR scheme based on the elliptic curve public key cryptography. Our formal proof shows that our BB2AR scheme satisfies the anonymous reporting and the anonymous rewarding simultaneously. Finally, we analyze its efficiency and provide its prototype implementation. From the comparison, our BB2AR scheme is more efficient and practical.

Rui Guo

Papers

Secure Attribute-Based Signature Scheme With Multiple Authorities for Blockchain in Electronic Health Records Systems

A Traceable Blockchain-Based Access Authentication System With Privacy Preservation in VANETs

Flexible and Efficient Blockchain-Based ABE Scheme With Multi-Authority for Medical on Demand in Telemedicine System

An Anti-Quantum E-Voting Protocol in Blockchain With Audit Function

Blockchain-Based Anonymous Reporting Scheme With Anonymous Rewarding