This book analyzes the fundamental issues faced when blockchain technology is applied to real-life applications. These concerns, not only in the realm of computer science, are caused by the nature of technological design. Blockchain is considered the foundation of a wide range of flexible ecosystems; its technology is an excellent mixture of mathematics, cryptography, incentive mechanisms, economics, and pertinent regulations. The book provides an essential understanding of why such fundamental issues arise, by revising the underlying theories. Blockchain theory is thus presented in an easy-to-understand, useful manner. Also explained is the reason why blockchain is hard to adopt for real-life problems but is valuable as a foundation for flexible ecosystems. Included are directions for solving those problems and finding suitable areas for blockchain applications in the future. The authors of this work are experts from a wide range of backgrounds such as cryptography, distributed computing, computer science, trust, identity, regulation, and standardization. Their contributions collected here will appeal to all who are interested in blockchain and the elements surrounding it.

This volume brings together a multidisciplinary group of scholars from diverse fields including computer science, engineering, archival science, law, business, psychology, economics, medicine and more to discuss the trade-offs between different “layers” in designing the use of blockchain/Distributed Ledger Technology (DLT) for social trust, trust in data and records, and trust in systems. Blockchain technology has emerged as a solution to the problem of trust in data and records, as well as trust in social, political and economic institutions, due to its profound potential as a digital trust infrastructure. Blockchain is a DLT in which confirmed and validated sets of transactions are stored in blocks that are chained together to make tampering more difficult and render records immutable. This book is dedicated to exploring and disseminating the latest findings on the relationships between socio-political and economic data, record-keeping, and technical aspects of blockchain.

Pairings on elliptic curves over finite fields are crucial for constructing various cryptographic schemes. The ηT pairing on supersingular curves over $GF(3^n)$ is particularly popular since it is efficiently implementable. Taking into account the Menezes-Okamoto-Vanstone attack, the discrete logarithm problem (DLP) in $GF(3^{6n})$ becomes a concern for the security of cryptosystems using ηT pairings in this case. In 2006, Joux and Lercier proposed a new variant of the function field sieve in the medium prime case, named JL06-FFS. We have, however, not yet found any practical implementations on JL06-FFS over $GF(3^{6n})$. Therefore, we first fulfill such an implementation and we successfully set a new record for solving the DLP in $GF(3^{6n})$, the DLP in GF(3^{6·71}) of 676-bit size. In addition, we also compare JL06-FFS and an earlier version, named JL02-FFS, with practical experiments. Our results confirm that the former is several times faster than the latter under certain conditions.

The first contribution of our paper is that we propose a platform, a design strategy, and evaluation criteria for a fair and consistent hardware evaluation of the second-round SHA-3 candidates. Using a SASEBO-GII field-programmable gate array (FPGA) board as a common platform, combined with well defined hardware and software interfaces, we compare all 256-bit version candidates with respect to area, throughput, latency, power, and energy consumption. Our approach defines a standard testing har- ness for SHA-3 candidates, including the interface specification for the SHA-3 module on our testing platform. The second contribution is that we provide both FPGA and 90-nm CMOS application-specific integrated circuit (ASIC) synthesis results and thereby are able to compare the results. Our third contribution is that we release the source code of all the candidates and by using a common, fixed, publicly available platform, our claimed results become reproducible and open for a public verification.