Emerging smart contract systems over decentralized cryptocurrencies allow mutually distrustful parties to transact safely without trusted third parties. In the event of contractual breaches or aborts, the decentralized blockchain ensures that honest parties obtain commensurate compensation. Existing systems, however, lack transactional privacy. All transactions, including flow of money between pseudonyms and amount transacted, are exposed on the blockchain. We present Hawk, a decentralized smart contract system that does not store financial transactions in the clear on the blockchain, thus retaining transactional privacy from the public's view. A Hawk programmer can write a private smart contract in an intuitive manner without having to implement cryptography, and our compiler automatically generates an efficient cryptographic protocol where contractual parties interact with the blockchain, using cryptographic primitives such as zero-knowledge proofs. To formally define and reason about the security of our protocols, we are the first to formalize the blockchain model of cryptography. The formal modeling is of independent interest. We advocate the community to adopt such a formal model when designing applications atop decentralized blockchains.

https://www.the-blockchain.com/docs/Hawk%20-%20The%20Blockchain%20Model%20of%20Cryptography%20and%20Privacy-Preserving%20Smart%20Contracts.pdf

Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts

Medical care has become one of the most indispensable parts of human lives, leading to a dramatic increase in medical big data. To streamline the diagnosis and treatment process, healthcare professionals are now adopting Internet of Things (IoT)-based wearable technology. Recent years have witnessed billions of sensors, devices, and vehicles being connected through the Internet. One such technology—remote patient monitoring—is common nowadays for the treatment and care of patients. However, these technologies also pose grave privacy risks and security concerns about the data transfer and the logging of data transactions. These security and privacy problems of medical data could result from a delay in treatment progress, even endangering the patient’s life. We propose the use of a blockchain to provide secure management and analysis of healthcare big data. However, blockchains are computationally expensive, demand high bandwidth and extra computational power, and are therefore not completely suitable for most resource-constrained IoT devices meant for smart cities. In this work, we try to resolve the above-mentioned issues of using blockchain with IoT devices. We propose a novel framework of modified blockchain models suitable for IoT devices that rely on their distributed nature and other additional privacy and security properties of the network. These additional privacy and security properties in our model are based on advanced cryptographic primitives. The solutions given here make IoT application data and transactions more secure and anonymous over a blockchain-based network.

https://www.mdpi.com/1424-8220/19/2/326/pdf

A Decentralized Privacy-Preserving Healthcare Blockchain for IoT

The Simon and Speck families of block ciphers were designed specifically to offer security on constrained devices, where simplicity of design is crucial. However, the intended use cases are diverse and demand flexibility in implementation. Simplicity, security, and flexibility are ever-present yet conflicting goals in cryptographic design. This paper outlines how these goals were balanced in the design of Simon and Speck.

The SIMON and SPECK lightweight block ciphers

We present a new tweakable block cipher family SKINNY, whose goal is to compete with NSA recent design SIMON in terms of hardware/software performances, while proving in addition much stronger security guarantees with regards to differential/linear attacks. In particular, unlike SIMON, we are able to provide strong bounds for all versions, and not only in the single-key model, but also in the related-key or related-tweak model. SKINNY has flexible block/key/tweak sizes and can also benefit from very efficient threshold implementations for side-channel protection. Regarding performances, it outperforms all known ciphers for ASIC round-based implementations, while still reaching an extremely small area for serial implementations and a very good efficiency for software and micro-controllers implementations SKINNY has the smallest total number of AND/OR/XOR gates used for encryption process.

Secondly, we present MANTIS, a dedicated variant of SKINNY for low-latency implementations, that constitutes a very efficient solution to the problem of designing a tweakable block cipher for memory encryption. MANTIS basically reuses well understood, previously studied, known components. Yet, by putting those components together in a new fashion, we obtain a competitive cipher to PRINCE in latency and area, while being enhanced with a tweak input.

/pdf/the-skinny-family-of-block-ciphers-and-its-low-latency-12yjnnzi8w.pdf

The SKINNY Family of Block Ciphers and Its Low-Latency Variant MANTIS

The Internet of Things (IoT) is rapidly spreading, reaching a multitude of different domains, including personal health care, environmental monitoring, home automation, smart mobility, and Industry 4.0. As a consequence, more and more IoT devices are being deployed in a variety of public and private environments, progressively becoming common objects of everyday life. It is hence apparent that, in such a scenario, cybersecurity becomes critical to avoid threats like leakage of sensible information, denial of service (DoS) attacks, unauthorized network access, and so on. Unfortunately, many low-end IoT commercial products do not usually support strong security mechanisms, and can hence be target of—or even means for—a number of security attacks. The aim of this article is to provide a broad overview of the security risks in the IoT sector and to discuss some possible counteractions. To this end, after a general introduction to security in the IoT domain, we discuss the specific security mechanisms adopted by the most popular IoT communication protocols. Then, we report and analyze some of the attacks against real IoT devices reported in the literature, in order to point out the current security weaknesses of commercial IoT solutions and remark the importance of considering security as an integral part in the design of IoT systems. We conclude this article with a reasoned comparison of the considered IoT technologies with respect to a set of qualifying security attributes, namely integrity, anonymity, confidentiality, privacy, access control, authentication, authorization, resilience, self organization.

IoT: Internet of Threats? A Survey of Practical Security Vulnerabilities in Real IoT Devices

The SIMON and SPECK Families of Lightweight Block Ciphers.

The U.S. National Security Agency (NSA) developed the Simon and Speck families of lightweight block ciphers as an aid for securing applications in very constrained environments where AES may not be suitable. This paper summarizes the algorithms, their design rationale, along with current cryptanalysis and implementation results.

/pdf/simon-and-speck-block-ciphers-for-the-internet-of-things-2vkz23sw1g.pdf

SIMON and SPECK: Block Ciphers for the Internet of Things.

The last several years have witnessed a surge of activity in lightweight cryptographic design Many lightweight block ciphers have been proposed, targeted mostly at hardware applications Typically software performance has not been a priority, and consequently software performance for many of these algorithms is unexceptional Simon and Speck are lightweight block cipher families developed by the US National Security Agency for high performance in constrained hardware and software environments In this paper, we discuss software performance and demonstrate how to achieve high performance implementations of Simon and Speck on the AVR family of 8-bit microcontrollers Both ciphers compare favorably to other lightweight block ciphers on this platform Indeed, Speck seems to have better overall performance than any existing block cipher — lightweight or not

/pdf/the-simon-and-speck-block-ciphers-on-avr-8-bit-jlzv4jkaji.pdf

The Simon and Speck Block Ciphers on AVR 8-Bit Microcontrollers

In 2011, prompted by potential U.S. government requirements for lightweight ciphers (e.g., SCADA and logistics applications) and concerns that existing cryptographic solutions were unnecessarily restrictive, a team of cryptographic designers was formed within the Information Assurance Research Laboratory of NSA’s Research Directorate, with the goal of designing foundational lightweight cryptographic block ciphers. SIMON and SPECK emerged from that research effort in 2013. See [Age16].

/pdf/notes-on-the-design-and-analysis-of-simon-and-speck-1c1oxvcfz3.pdf

Bryan Weeks

Papers

The SIMON and SPECK Families of Lightweight Block Ciphers.

The SIMON and SPECK lightweight block ciphers

SIMON and SPECK: Block Ciphers for the Internet of Things.

The Simon and Speck Block Ciphers on AVR 8-Bit Microcontrollers

Notes on the design and analysis of SIMON and SPECK.