Finding SHA-2 characteristics: searching through a minefield of contradictions
Florian Mendel,Tomislav Nad,Martin Schläffer +2 more
- pp 288-307
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This paper presents the first automated tool for finding complex differential characteristics in SHA-2 and shows that the techniques on SHA-1 cannot directly be applied toSHA-2, and shows how to overcome difficulties by including the search for conforming message pairs in thesearch for differential characteristics.Abstract:
In this paper, we analyze the collision resistance of SHA-2 and provide the first results since the beginning of the NIST SHA-3 competition. We extend the previously best known semi-free-start collisions on SHA-256 from 24 to 32 (out of 64) steps and show a collision attack for 27 steps. All our attacks are practical and verified by colliding message pairs. We present the first automated tool for finding complex differential characteristics in SHA-2 and show that the techniques on SHA-1 cannot directly be applied to SHA-2. Due to the more complex structure of SHA-2 several new problems arise. Most importantly, a large amount of contradicting conditions occur which render most differential characteristics impossible. We show how to overcome these difficulties by including the search for conforming message pairs in the search for differential characteristics.read more
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BookDOI
Advances in Cryptology -- EUROCRYPT 2013
Thomas Johansson,Phong Q. Nguyen +1 more
TL;DR: 41 full papers included in this volume deal with cryptanalysis of hash functions, side-channel attacks, number theory, lattices, public key encryption, digital signatures, homomorphic cryptography, quantum cryptography, storage, tools, and secure computation.
Book ChapterDOI
MILP-Based Automatic Search Algorithms for Differential and Linear Trails for Speck
TL;DR: This paper proposes an MILP-based method for automatic search for differential characteristics and linear approximations in ARX ciphers and presents a method to describe the differential characteristic and linear approximation with linear inequalities under the assumptions of independent inputs to the modular addition and independent rounds.
Book ChapterDOI
Improving Local Collisions: New Attacks on Reduced SHA-256
TL;DR: In this paper, the authors focus on the construction of semi-free-start collisions for SHA-256, and show how to turn them into collisions using a two-block approach.
Book ChapterDOI
Automatic Search for Differential Trails in ARX Ciphers
Alex Biryukov,Vesselin Velichkov +1 more
TL;DR: In this article, a tool for automatic search for differential trails in ARX ciphers is proposed, which can be applied to the block cipthers TEA, XTEA, SPECK and RAIDEN.
Book ChapterDOI
Analysis of differential attacks in ARX constructions
TL;DR: New multi-bit constraints to describe differential characteristics in ARX designs more accurately, and quartet constraints to analyze boomerang attacks, and how to propagate those constraints are described.
References
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Book ChapterDOI
Finding collisions in the full SHA-1
TL;DR: This is the first attack on the full 80-step SHA-1 with complexity less than the 280 theoretical bound, and it is shown that collisions ofSHA-1 can be found with complexityLess than 269 hash operations.
Book ChapterDOI
How to break MD5 and other hash functions
Xiaoyun Wang,Hongbo Yu +1 more
TL;DR: A new powerful attack on MD5 is presented, which unlike most differential attacks, does not use the exclusive-or as a measure of difference, but instead uses modular integer subtraction as the measure.
Book ChapterDOI
Cryptanalysis of the hash functions MD4 and RIPEMD
TL;DR: In this article, a chosen-message pre-image attack on MD4 with complexity below 28 was presented, where the complexity is only a single MD4 computation and a random message is a weak message with probability 2−2 to 2−6.
Book ChapterDOI
Efficient collision search attacks on SHA-0
TL;DR: Using the new techniques, this paper can find collisions of the full 80-step SHA-0 with complexity less than 239 hash operations.
Algorithms for the Satisfiability (SAT) Problem: A Survey,
TL;DR: This survey presents a general framework (an algorithm space) that integrates existing SAT algorithms into a unified perspective and describes sequential and parallel SAT algorithms including variable splitting, resolution, local search, global optimization, mathematical programming, and practical SAT algorithms.