We present the hash function BLAKE2, an improved version of the SHA-3 finalist BLAKE optimized for speed in software. Target applications include cloud storage, intrusion detection, or version control systems. BLAKE2 comes in two main flavors: BLAKE2b is optimized for 64-bit platforms, and BLAKE2s for smaller architectures. On 64bit platforms, BLAKE2 is often faster than MD5, yet provides security similar to that of SHA-3: up to 256-bit collision resistance, immunity to length extension, indifferentiability from a random oracle, etc. We specify parallel versions BLAKE2bp and BLAKE2sp that are up to 4 and 8 times faster, by taking advantage of SIMD and/or multiple cores. BLAKE2 reduces the RAM requirements of BLAKE down to 168 bytes, making it smaller than any of the five SHA-3 finalists, and 32% smaller than BLAKE. Finally, BLAKE2 provides a comprehensive support for tree-hashing as well as keyed hashing (be it in sequential or tree mode).

Abstract.A popular approach to tweakable blockcipher design is via masking, where a certain primitive (a blockcipher or a permutation) is preceded and followed by an easy-to-compute tweak-dependent mask. In this work, we revisit the principle of masking. We do so alongside the introduction of the tweakable Even-Mansour construction MEM. Its masking function combines the advantages of word-oriented LFSRand powering-up-based methods. We show in particular how recent advancements in computing discrete logarithms over finite fields of characteristic 2 can be exploited in a constructive way to realize highly efficient, constant-time masking functions. If the masking satisfies a set of simple conditions, then MEM is a secure tweakable blockcipher up to the birthday bound. The strengths of MEM are exhibited by the design of fully parallelizable authenticated encryption schemes OPP (nonce-respecting) and MRO (misuse-resistant). If instantiated with a reduced-round BLAKE2b permutation, OPP and MRO achieve speeds up to 0.55 and 1.06 cycles per byte on the Intel Haswell microarchitecture, and are able to significantly outperform their closest competitors.

This paper introduces NORX, a novel authenticated encryption scheme supporting arbitrary parallelism degree and based on ARX primitives, yet not using modular additions. NORX has a unique parallel architecture based on the monkeyDuplex construction, with an original domain separation scheme for a simple processing of header/payload-/trailer data. Furthermore, NORX specifies a dedicated datagram to facilitate interoperability and avoid users the trouble of defining custom encoding and signalling. NORX was optimized for efficiency in both software and hardware, with a SIMD-friendly core, almost byte-aligned rotations, no secret-dependent memory lookups, and only bitwise operations. On a Haswell processor, a serial version of NORX runs at 2.51 cycles per byte. Simulations of a hardware architecture for 180 nm UMC ASIC give a throughput of approximately 10 Gbps at 125 MHz.

Abstract. At CRYPTO 2016, Cogliati and Seurin introduced the Encrypted Davies-Meyer construction, p2(p1(x)⊕x) for two n-bit permutations p1, p2, and proved security up to 2 2n/3 . We present an improved security analysis up to 2 n /(67n). Additionally, we introduce the dual of the Encrypted Davies-Meyer construction, p2(p1(x)) ⊕ p1(x), and prove even tighter security for this construction: 2 n /67. We finally demonstrate that the analysis neatly generalizes to prove almost optimal security of the Encrypted Wegman-Carter with Davies-Meyer MAC construction. Central to our analysis is a modernization of Patarin's mirror theorem and an exposition of how it relates to fundamental cryptographic problems.

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