Background: Blockchain can be described as an immutable ledger, logging data entries in a decentralized manner. This new technology has been suggested to disrupt a wide range of data-driven domains, including the health domain. Objective: The purpose of this study was to systematically review, assess and synthesize peer-reviewed publications utilizing/proposing to utilize blockchain to improve processes and services in healthcare, health sciences and health education. Method: A structured literature search on the topic was conducted in October 2018 relevant bibliographic databases. Result: 39 publications fulfilled the inclusion criteria. The result indicates that Electronic Health Records and Personal Health Records are the most targeted areas using blockchain technology. Access control, interoperability, provenance and data integrity are all issues that are meant to be improved by blockchain technology in this field. Ethereum and Hyperledger fabric seem to be the most used platforms/frameworks in this domain. Conclusion: This study shows that the endeavors of using blockchain technology in the health domain are increasing exponentially. There are areas within the health domain that potentially could be highly impacted by blockchain technology.
Keywords: Blockchain | Health systems | Scoping review | Distributed ledger

Instant Messaging (IM) offers real-time communications between two or more participants on Internet. Nowadays, most IMs take place on mobile applications, such as WhatsApp, WeChat, Viber and Facebook Messenger, which have more users than social networks, such as Twitter and Facebook. Among the applications of IMs, online shopping has become a part of our everyday life, primarily those who are busiest. However, transaction disputes are often occurred online shopping. Since most IMs are centralized and message history is not stored in the center, the messaging between users and owners of online shops are not reliable and traceable. In China, online shopping sales have soared from practically zero in 2003 to nearly 600 hundred million dollars last year, and now top those in the United States. It is very crucial to secure the instant messaging in online shopping in China. We present techniques to exploit blockchain and machine learning algorithms to secure instant messaging. Since the cryptography of Chinese national standard is encouraged to adopt in security applications of China, we propose a blockchain-based IM scheme with the Chinese cryptographic bases. First, we design a message authentication model based on SM2 to avoid the counterfeit attack and replay attack. Second, we design a cryptographic hash mode based on SM3 to verify the integrity of message. Third, we design a message encryption model based on SM4 to protect the privacy of users. Besides, we propose a method based on machine learning algorithms to monitor the activity on blockchain to detect anomaly. To prove and verify the blockchain-based IM scheme, a blockchain-based IM system has been designed on Linux platforms. The implementation result shows that it is a practical and secure IM system, which can be applied to a variety of instant messaging applications directly.
Keywords: Instant Messaging (IM) | BlockChain | Machine learning | Distributed Ledger Technology (DLT) | Safety and security

Consensus is a fundamental problem of distributed computing. While this problem has been known to be unsolvable since 1985, existing protocols were designed these past three decades to solve consensus under various assumptions. Today, with the recent advent of blockchains, various consensus implementations were proposed to make replicas reach an agreement on the order of transactions updating what is often referred to as a distributed ledger. Very little work has however been devoted to explore its theoretical ramifications. As a result existing proposals are sometimes misunderstood and it is often unclear whether the problems arising during their executions are due to implementation bugs or more fundamental design issues. In this paper, we discuss the mainstream blockchain consensus algorithms and how the classic Byzantine consensus can be revisited for the blockchain context. In particular, we discuss proof-of-work consensus and illustrate the differences between the Bitcoin and the Ethereum proof-of-work consensus algorithms. Based on these definitions, we warn about the dangers of using these blockchains without understanding precisely the guarantees their consensus algorithm offers. In particular, we survey attacks against the Bitcoin and the Ethereum consensus algorithms. We finally discuss the advantage of the recent Blockchain Byzantine consensus definition over previous definitions, and the promises offered by emerging consistent blockchains.
Keywords: Algorithms | Proof-of-work | Blockchain consensus | Scalability

This conceptual paper explores the impact of blockchain technology on public sector processes through the lens of information security. It includes an overview of the evolution of e-government, a synopsis of existing applications of blockchain technology, and innovative blockchain developments. We utilize the Confidentiality- Integrity-Accessibility (CIA) triad to guide our discussion of the security, governance, and regulatory implications of this technology. Leveraging the CIA triad model, we provide context for public managers who may consider blockchain technologies, and we highlight certain advantages arising from the “non-reputability” of distributed ledgers. In particular, we highlight the advantages of blockchain technologies with regards to non-reputability to help public managers understand how to best leverage blockchain technology to transform operations.
Keywords: Blockchain technology | Public sector applications | Government | Security triad