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

The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

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

Systems code is often written in low-level languages like C/C++, which offer many benefits but also delegate memory management to programmers. This invites memory safety bugs that attackers can exploit to divert control flow and compromise the system. Deployed defense mechanisms (e.g., ASLR, DEP) are incomplete, and stronger defense mechanisms (e.g., CFI) often have high overhead and limited guarantees [19, 15, 9].We introduce code-pointer integrity (CPI), a new design point that guarantees the integrity of all code pointers in a program (e.g., function pointers, saved return addresses) and thereby prevents all control-flow hijack attacks, including return-oriented programming. We also introduce code-pointer separation (CPS), a relaxation of CPI with better performance properties. CPI and CPS offer substantially better security-to-overhead ratios than the state of the art, they are practical (we protect a complete FreeBSD system and over 100 packages like apache and postgresql), effective (prevent all attacks in the RIPE benchmark), and efficient: on SPEC CPU2006, CPS averages 1.2% overhead for C and 1.9% for C/C++, while CPI's overhead is 2.9% for C and 8.4% for C/C++.A prototype implementation of CPI and CPS can be obtained from http://levee.epfl.ch.

/pdf/code-pointer-integrity-2gu5mwg209.pdf

Code-pointer integrity

Salsa20 is a family of 256-bit stream ciphers designed in 2005 and submitted to eSTREAM, the ECRYPT Stream Cipher Project. Salsa20 has progressed to the third round of eSTREAM without any changes. The 20-round stream cipher Salsa20/20 is consistently faster than AES and is recommended by the designer for typical cryptographic applications. The reduced-round ciphers Salsa20/12 and Salsa20/8 are among the fastest 256-bit stream ciphers available and are recommended for applications where speed is more important than confidence. The fastest known attacks use ≈ 2153simple operations against Salsa20/7, ≈ 2249simple operations against Salsa20/8, and ≈ 2255simple operations against Salsa20/9, Salsa20/10, etc. In this paper, the Salsa20 designer presents Salsa20 and discusses the decisions made in the Salsa20 design.

/pdf/the-salsa20-family-of-stream-ciphers-4la86gmtaq.pdf

The Salsa20 Family of Stream Ciphers

SipHash is a family of pseudorandom functions optimized for short inputs. Target applications include network traffic authentication and hash-table lookups protected against hash-flooding denial-of-service attacks. SipHash is simpler than MACs based on universal hashing, and faster on short inputs. Compared to dedicated designs for hash-table lookup, SipHash has well-defined security goals and competitive performance. For example, SipHash processes a 16-byte input with a fresh key in 140 cycles on an AMD FX-8150 processor, which is much faster than state-of-the-art MACs. We propose that hash tables switch to SipHash as a hash function.

/pdf/siphash-a-fast-short-input-prf-u9qstn38jx.pdf

SipHash : a fast short-input PRF

The need for lightweight (that is, compact, low-power, low-energy) cryptographic hash functions has been repeatedly expressed by professionals, notably to implement cryptographic protocols in RFID technology. At the time of writing, however, no algorithm exists that provides satisfactory security and performance. The ongoing SHA-3 Competition will not help, as it concerns general-purpose designs and focuses on software performance. This paper thus proposes a novel design philosophy for lightweight hash functions, based on the sponge construction in order to minimize memory requirements. Inspired by the stream cipher Grain and by the block cipher KATAN (amongst the lightest secure ciphers), we present the hash function family Quark, composed of three instances: u-Quark, d-Quark, and s-Quark. As a sponge construction, Quark can be used for message authentication, stream encryption, or authenticated encryption. Our hardware evaluation shows that Quark compares well to previous tentative lightweight hash functions. For example, our lightest instance u-Quark conjecturally provides at least 64-bit security against all attacks (collisions, multicollisions, distinguishers, etc.), fits in 1379 gate-equivalents, and consumes on average 2.44 μW at 100 kHz in 0.18 μm ASIC. For 112-bit security, we propose s-Quark, which can be implemented with 2296 gate-equivalents with a power consumption of 4.35 μW.

/pdf/quark-a-lightweight-hash-461jjxjajg.pdf

Quark: A Lightweight Hash

BLAKE is our proposal for SHA-3. BLAKE entirely relies on previously analyzed components: it uses the HAIFA iteration mode and builds its compression function on the ChaCha core function. BLAKE resists generic second-preimage attacks, length extension, and sidechannel attacks. Theoretical and empirical security guarantees are given, against structural and differential attacks. BLAKE hashes on a Core 2 Duo at 12 cycles/byte, and on a 8-bit PIC microcontroller at 400 cycles/byte. In hardware BLAKE can be implemented in less than 9900 gates, and reaches a throughput of 6 Gbps. FHNW, Windisch, Switzerland, jeanphilippe.aumasson@gmail.com ETHZ, Zurich, Switzerland, henzen@iis.ee.ethz.ch FHNW, Windisch, Switzerland, willi.meier@fhnw.ch Loughborough University, UK, r.phan@lboro.ac.uk

SHA-3 proposal BLAKE

CRYPTO 2008 saw the introduction of the hash function MD6 and of cube attacks, a type of algebraic attack applicable to cryptographic functions having a low-degree algebraic normal form over GF(2). This paper applies cube attacks to reduced round MD6, finding the full 128-bit key of a 14-round MD6 with complexity 222 (which takes less than a minute on a single PC). This is the best key recovery attack announced so far for MD6. We then introduce a new class of attacks called cube testers, based on efficient property-testing algorithms, and apply them to MD6 and to the stream cipher Trivium. Unlike the standard cube attacks, cube testers detect nonrandom behavior rather than performing key extraction, but they can also attack cryptographic schemes described by nonrandom polynomials of relatively high degree. Applied to MD6, cube testers detect nonrandomness over 18 rounds in 217 complexity; applied to a slightly modified version of the MD6 compression function, they can distinguish 66 rounds from random in 224 complexity. Cube testers give distinguishers on Trivium reduced to 790 rounds from random with 230 complexity and detect nonrandomness over 885 rounds in 227, improving on the original 767-round cube attack.

/pdf/cube-testers-and-key-recovery-attacks-on-reduced-round-md6-2ibarjrgjm.pdf

Cube Testers and Key Recovery Attacks on Reduced-Round MD6 and Trivium

The need for lightweight cryptographic hash functions has been repeatedly expressed by application designers, notably for implementing RFID protocols. However not many designs are available, and the ongoing SHA-3 Competition probably won't help, as it concerns general-purpose designs and focuses on software performance. In this paper, we thus propose a novel design philosophy for lightweight hash functions, based on a single security level and on the sponge construction, to minimize memory requirements. Inspired by the lightweight ciphers Grain and KATAN, we present the hash function family QUARK, composed of the three instances U-QUARK, D-QUARK, and T-QUARK. Hardware benchmarks show that QUARK compares well to previous lightweight hashes. For example, our lightest instance U-QUARK conjecturally provides at least 64-bit security against all attacks (collisions, multicollisions, distinguishers, etc.), fits in 1379 gate-equivalents, and consumes in average 2.44 µW at 100 kHz in 0.18 µm ASIC. For 112- bit security, we propose T-QUARK, which we implemented with 2296 gate-equivalents.

/pdf/quark-a-lightweight-hash-3j5ekv1nxe.pdf

Jean-Philippe Aumasson

Papers

SipHash : a fast short-input PRF

Quark: A Lightweight Hash

SHA-3 proposal BLAKE

Cube Testers and Key Recovery Attacks on Reduced-Round MD6 and Trivium

QUARK: a lightweight hash