National Institute of Standards and Technology における超伝導研究及び生活

Usually, a proof of a theorem contains more knowledge than the mere fact that the theorem is true. For instance, to prove that a graph is Hamiltonian it suffices to exhibit a Hamiltonian tour in it; however, this seems to contain more knowledge than the single bit Hamiltonian/non-Hamiltonian.In this paper a computational complexity theory of the “knowledge” contained in a proof is developed. Zero-knowledge proofs are defined as those proofs that convey no additional knowledge other than the correctness of the proposition in question. Examples of zero-knowledge proof systems are given for the languages of quadratic residuosity and 'quadratic nonresiduosity. These are the first examples of zero-knowledge proofs for languages not known to be efficiently recognizable.

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The knowledge complexity of interactive proof-systems

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

Internet of Things (IoT) allows billions of physical objects to be connected to collect and exchange data for offering various applications, such as environmental monitoring, infrastructure management, and home automation. On the other hand, IoT has unsupported features (e.g., low latency, location awareness, and geographic distribution) that are critical for some IoT applications, including smart traffic lights, home energy management and augmented reality. To support these features, fog computing is integrated into IoT to extend computing, storage and networking resources to the network edge. Unfortunately, it is confronted with various security and privacy risks, which raise serious concerns towards users. In this survey, we review the architecture and features of fog computing and study critical roles of fog nodes, including real-time services, transient storage, data dissemination and decentralized computation. We also examine fog-assisted IoT applications based on different roles of fog nodes. Then, we present security and privacy threats towards IoT applications and discuss the security and privacy requirements in fog computing. Further, we demonstrate potential challenges to secure fog computing and review the state-of-the-art solutions used to address security and privacy issues in fog computing for IoT applications. Finally, by defining several open research issues, it is expected to draw more attention and efforts into this new architecture.

Securing Fog Computing for Internet of Things Applications: Challenges and Solutions

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

Differential and linear cryptanalysis are two of the most powerful techniques to analyze symmetric-key primitives. For modern ciphers, resistance against these attacks is therefore a mandatory design criterion. In this paper, we propose a novel technique to prove security bounds against both differential and linear cryptanalysis. We use mixed-integer linear programming (MILP), a method that is frequently used in business and economics to solve optimization problems. Our technique significantly reduces the workload of designers and cryptanalysts, because it only involves writing out simple equations that are input into an MILP solver. As very little programming is required, both the time spent on cryptanalysis and the possibility of human errors are greatly reduced. Our method is used to analyze Enocoro-128v2, a stream cipher that consists of 96 rounds. We prove that 38 rounds are sufficient for security against differential cryptanalysis, and 61 rounds for security against linear cryptanalysis. We also illustrate our technique by calculating the number of active S-boxes for AES.

Differential and linear cryptanalysis using mixed-integer linear programming

NIST-approved cryptographic standards were designed to perform well on general-purpose computers. In recent years, there has been increased deployment of small computing devices that have limited resources with which to implement cryptography. When current NIST-approved algorithms can be engineered to fit into the limited resources of constrained environments, their performance may not be acceptable. For these reasons, NIST started a lightweight cryptography project that was tasked with learning more about the issues and developing a strategy for the standardization of lightweight cryptographic algorithms. This report provides an overview of the lightweight cryptography project at NIST, and describes plans for the standardization of lightweight cryptographic algorithms.

/pdf/report-on-lightweight-cryptography-ho94bt19z7.pdf

Report on Lightweight Cryptography

We propose Chaskey: a very efficient Message Authentication Code (MAC) algorithm for 32-bit microcontrollers. It is intended for applications that require 128-bit security, yet cannot implement standard MAC algorithms because of stringent requirements on speed, energy consumption, or code size. Chaskey is a permutation-based MAC algorithm that uses the Addition-Rotation-XOR (ARX) design methodology. We prove that Chaskey is secure in the standard model, based on the security of an underlying Even-Mansour block cipher. Chaskey is designed to perform well on a wide range of 32-bit microcontrollers. Our benchmarks show that on the ARM Cortex-M3/M4, our Chaskey implementation reaches a speed of 7.0 cycles/byte, compared to 89.4 cycles/byte for AES-128-CMAC. For the ARM Cortex-M0, our benchmark results give 16.9 cycles/byte and 136.5 cycles/byte for Chaskey and AES-128-CMAC respectively.

https://lirias.kuleuven.be/bitstream/123456789/463157/2/article-2441.pdf

Chaskey: An Efficient MAC Algorithm for 32-bit Microcontrollers

/pdf/chaskey-an-efficient-mac-algorithm-for-32-bit-3qjfjri8e9.pdf

https://lirias.kuleuven.be/bitstream/123456789/324075/2/article-2080.pdf

Nicky Mouha

Papers

Differential and linear cryptanalysis using mixed-integer linear programming

Report on Lightweight Cryptography

Chaskey: An Efficient MAC Algorithm for 32-bit Microcontrollers

Chaskey: An Efficient MAC Algorithm for 32-bit Microcontrollers

Differential and Linear Cryptanalysis using Mixed-Integer Linear Programming