There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

We present a new block cipher LED. While dedicated to compact hardware implementation, and offering the smallest silicon footprint among comparable block ciphers, the cipher has been designed to simultaneously tackle three additional goals. First, we explore the role of an ultra-light (in fact non-existent) key schedule. Second, we consider the resistance of ciphers, and LED in particular, to related-key attacks: we are able to derive simple yet interesting AES-like security proofs for LED regarding related- or single-key attacks. And third, while we provide a block cipher that is very compact in hardware, we aim to maintain a reasonable performance profile for software implementation.

The LED block cipher

Smart grids equipped with bi-directional communication flow are expected to provide more sophisticated consumption monitoring and energy trading. However, the issues related to the security and privacy of consumption and trading data present serious challenges. In this paper we address the problem of providing transaction security in decentralized smart grid energy trading without reliance on trusted third parties. We have implemented a proof-of-concept for decentralized energy trading system using blockchain technology, multi-signatures, and anonymous encrypted messaging streams, enabling peers to anonymously negotiate energy prices and securely perform trading transactions. We conducted case studies to perform security analysis and performance evaluation within the context of the elicited security and privacy requirements.

Security and Privacy in Decentralized Energy Trading Through Multi-Signatures, Blockchain and Anonymous Messaging Streams

Since Rijndael was chosen as the Advanced Encryption Standard (AES), improving upon 7-round attacks on the 128-bit key variant (out of 10 rounds) or upon 8-round attacks on the 192/256-bit key variants (out of 12/14 rounds) has been one of the most difficult challenges in the cryptanalysis of block ciphers for more than a decade. In this paper, we present the novel technique of block cipher cryptanalysis with bicliques, which leads to the following results:

 

The first key recovery method for the full AES-128 with computational complexity 2126.1.

The first key recovery method for the full AES-192 with computational complexity 2189.7.

The first key recovery method for the full AES-256 with computational complexity 2254.4.

Key recovery methods with lower complexity for the reduced-round versions of AES not considered before, including cryptanalysis of 8-round AES-128 with complexity 2124.9.

Preimage search for compression functions based on the full AES versions faster than brute force.

In contrast to most shortcut attacks on AES variants, we do not need to assume related-keys. Most of our techniques only need a very small part of the codebook and have low memory requirements, and are practically verified to a large extent. As our cryptanalysis is of high computational complexity, it does not threaten the practical use of AES in any way.

/pdf/biclique-cryptanalysis-of-the-full-aes-pi8uwf8n7d.pdf

Biclique cryptanalysis of the full AES

We present a detailed security analysis of the CAESAR candidate Ascon. Amongst others, cube-like, differential and linear cryptanalysis are used to evaluate the security of Ascon. Our results are practical key-recovery attacks on round-reduced versions of Ascon-128, where the initialization is reduced to 5 out of 12 rounds. Theoretical keyrecovery attacks are possible for up to 6 rounds of initialization. Moreover, we present a practical forgery attack for 3 rounds of the finalization, a theoretical forgery attack for 4 rounds finalization and zero-sum distinguishers for the full 12-round Ascon permutation. Besides, we present the first results regarding linear cryptanalysis of Ascon, improve upon the results of the designers regarding differential cryptanalysis, and prove bounds on the minimum number of (linearly and differentially) active Sboxes for the Ascon permutation.

/pdf/cryptanalysis-of-ascon-1c2vchiv80.pdf

Cryptanalysis of Ascon.

SIMD is one of the round 2 candidates of the public SHA-3 competition hosted by NIST. It was designed by Leurent et al.. In this paper, we present a distinguisher attack on the compression function of SIMD-512. By linearizing the compression function we construct a linear code. Using techniques from coding theory to search for low Hamming weight codewords, we can find differential characteristics with low Hamming weight (and hence high probability). In the attack the differences are introduced only in the IV. Such a characteristic is the base for our distinguisher, which can distinguish the compression function of SIMD-512 from random with a complexity of 5·2425.28 compression function calls. Furthermore, we can distinguish the output transformation of SIMD-512 from random with a complexity of about 22·2425.28 compression function calls. So far this is the first cryptanalytic result for the SIMD hash function.

https://lirias.kuleuven.be/bitstream/123456789/329814/2/article-2096.pdf

A Distinguisher for the Compression Function of SIMD-512

This report was produced in partial fulfillment of contract ICT-2007-216676 (ECRYPT II), sponsored by the European Commission through the ICT Programme. The information in
this paper is provided as is, and no warranty is given or implied that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and liability. We present a short overview of the recent results on the five finalists for NIST's SHA-3
competition. The next five chapters treat each one of the finalists.

Intermediate Status Report

Since the first demonstration of fault attacks by Boneh et al. on RSA, a multitude of fault attack techniques on various cryptosystems have been proposed. Most of these techniques, like Differential Fault Analysis, Safe Error Attacks, and Collision Fault Analysis, have the requirement to process two inputs that are either identical or related, in order to generate pairs of correct/faulty ciphertexts. However, when targeting authenticated encryption schemes, this is in practice usually precluded by the unique nonce required by most of these schemes.

/pdf/statistical-fault-attacks-on-nonce-based-authenticated-58azkshv3l.pdf

Statistical Fault Attacks on Nonce-Based Authenticated Encryption Schemes

The recently started SHA-3 competition in order to find a new secure hash standard and thus a replacement for SHA-1/SHA-2 has attracted a lot of interest in the academic world as well as in industry. There are 51 round one candidates building on sometimes very different principles.

In this paper, we show how to attack two of the 51 round one hash functions. The attacks have in common that they exploit structural weaknesses in the design of the hash function and are independent of the underlying compression function. First, we present a preimage attack on the hash function Blender-n . It has a complexity of about n ·2 n /2 and negligible memory requirements. Secondly, we show practical collision and preimage attacks on DCH-n . To be more precise, we can trivially construct a (28 + 2)-block collision for DCH-n and a 1297-block preimage with only 521 compression function evaluations. The attacks on both hash functions work for all output sizes and render the hash functions broken.

https://lirias.kuleuven.be/bitstream/123456789/329813/2/article-2095.pdf

Florian Mendel

Papers

Cryptanalysis of Ascon.

A Distinguisher for the Compression Function of SIMD-512

Intermediate Status Report

Statistical Fault Attacks on Nonce-Based Authenticated Encryption Schemes

Structural Attacks on Two SHA-3 Candidates: Blender-n and DCH-n