Martin Schläffer

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Grøstl is a SHA-3 candidate proposal. Grøstl is an iterated hash function with a compression function built from two fixed, large, distinct permutations. The design of Grøstl is transparent and based on principles very different from those used in the SHA-family. The two permutations are constructed using the wide trail design strategy, which makes it(More)
Hardware implementations of cryptographic algorithms are vulnerable to side-channel attacks. Side-channel attacks that are based on multiple measurements of the same operation can be countered by employing masking techniques. Many protection measures depart from an idealized hardware model that is very expensive to meet with real hardware. In particular,(More)
In this work, we propose the rebound attack, a new tool for the cryptanalysis of hash functions. The idea of the rebound attack is to use the available degrees of freedom in a collision attack to efficiently bypass the low probability parts of a differential trail. The rebound attack consists of an inbound phase with a match-in-the-middle part to exploit(More)
Whirlpool is a hash function based on a block cipher that can be seen as a scaled up variant of the AES. The main difference is the (compared to AES) extremely conservative key schedule. In this work, we present a distinguishing attack on the full compression function of Whirlpool. We obtain this result by improving the rebound attack on reduced Whirlpool(More)
iii Abstract The National Institute of Standards and Technology (NIST) opened a public competition on November 2, 2007, to develop a new cryptographic hash algorithm – SHA-3, which will augment the hash algorithms specified in the Federal Information Processing Standard (FIPS) 180-4, Secure Hash Standard (SHS). The competition was NIST's response to(More)
The ground-breaking results of Wang et al. have attracted a lot of attention to the collision resistance of hash functions. In their articles, Wang et al. give input differences, differential paths and the corresponding conditions that allow to find collisions with a high probability. However, Wang et al. do not explain how these paths were found. The(More)
In this paper, we propose two new ways to mount attacks on the SHA-3 candidates Grøstl, and ECHO, and apply these attacks also to the AES. Our results improve upon and extend the rebound attack. Using the new techniques, we are able to extend the number of rounds in which available degrees of freedom can be used. As a result, we present the first attack on(More)
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.(More)
We introduce the rebound attack as a variant of differential cryptanalysis on hash functions and apply it to the hash function Whirlpool, standardized by ISO/IEC. We give attacks on reduced variants of the 10-round Whirlpool hash function and compression function. Our results are collisions for 5.5 and near-collisions for 7.5 rounds on the hash function, as(More)
In this work we present first results for the hash function of ECHO. We provide a subspace distinguisher for 5 rounds, near-collisions on 4.5 rounds and collisions for 4 out of 8 rounds of the ECHO-256 hash function. The complexities are 2 compression function calls for the distinguisher and near-collision attack, and 2 for the collision attack. The memory(More)