183 research outputs found
The role of fingerprints in the coding of tactile information probed with a biomimetic sensor
In humans, the tactile perception of fine textures (spatial scale <200
micrometers) is mediated by skin vibrations generated as the finger scans the
surface. To establish the relationship between texture characteristics and
subcutaneous vibrations, a biomimetic tactile sensor has been designed whose
dimensions match those of the fingertip. When the sensor surface is patterned
with parallel ridges mimicking the fingerprints, the spectrum of vibrations
elicited by randomly textured substrates is dominated by one frequency set by
the ratio of the scanning speed to the interridge distance. For human touch,
this frequency falls within the optimal range of sensitivity of Pacinian
afferents, which mediate the coding of fine textures. Thus, fingerprints may
perform spectral selection and amplification of tactile information that
facilitate its processing by specific mechanoreceptors.Comment: 25 pages, 11 figures, article + supporting materia
Clustering effect in Simon and Simeck
SIMON and SIMECK are two lightweight block ciphers with a simple round function using only word rotations and a bit-wise AND operation. Previous work has shown a strong clustering effect for differential and linear cryptanalysis, due to the existence of many trails with the same inputs and outputs.
In this paper, we explore this clustering effect by exhibiting a class of high probability differential and linear trails where the active bits stay in a fixed window of w bits. Instead of enumerating a set of good trails contributing to a differential or a linear approximation, we compute the probability distribution over this space, including all trails in the class.
This results in stronger distinguishers than previously proposed, and we describe key recovery attacks against SIMON and SIMECK improving the previous results by u
Quantum linearization attacks
Recent works have shown that quantum period-finding can be used to break many popular constructions (some block ciphers such as Even-Mansour, multiple MACs and AEs...) in the superposition query model. So far, all the constructions broken exhibited a strong algebraic structure, which enables to craft a periodic function of a single input block. Recoverin
From Scattering Amplitudes to the Dilatation Generator in N=4 SYM
The complete spin chain representation of the planar N=4 SYM dilatation
generator has long been known at one loop, where it involves leading
nearest-neighbor 2 -> 2 interactions. In this work we use superconformal
symmetry to derive the unique solution for the leading L -> 2 interactions of
the planar dilatation generator for arbitrarily large L. We then propose that
these interactions are given by the scattering operator that has N=4 SYM
tree-level scattering amplitudes as matrix elements. We provide compelling
evidence for this proposal, including explicit checks for L=2,3 and a proof of
consistency with superconformal symmetry.Comment: 39 pages, v2: reference added and minor changes, published versio
Quantum Spectral Curve at Work: From Small Spin to Strong Coupling in N=4 SYM
We apply the recently proposed quantum spectral curve technique to the study
of twist operators in planar N=4 SYM theory. We focus on the small spin
expansion of anomalous dimensions in the sl(2) sector and compute its first two
orders exactly for any value of the 't Hooft coupling. At leading order in the
spin S we reproduced Basso's slope function. The next term of order S^2
structurally resembles the Beisert-Eden-Staudacher dressing phase and takes
into account wrapping contributions. This expansion contains rich information
about the spectrum of local operators at strong coupling. In particular, we
found a new coefficient in the strong coupling expansion of the Konishi
operator dimension and confirmed several previously known terms. We also
obtained several new orders of the strong coupling expansion of the BFKL
pomeron intercept. As a by-product we formulated a prescription for the correct
analytical continuation in S which opens a way for deriving the BFKL regime of
twist two anomalous dimensions from AdS/CFT integrability.Comment: 53 pages, references added; v3: due to a typo in the coefficients C_2
and D_2 on page 29 we corrected the rational part of the strong coupling
predictions in equations (1.5-6), (6.22-24), (6.27-30) and in Table
Quark--anti-quark potential in N=4 SYM
We construct a closed system of equations describing the quark--anti-quark
potential at any coupling in planar N=4 supersymmetric Yang-Mills theory. It is
based on the Quantum Spectral Curve method supplemented with a novel type of
asymptotics. We present a high precision numerical solution reproducing the
classical and one-loop string predictions very accurately. We also analytically
compute the first 7 nontrivial orders of the weak coupling expansion.
Moreover, we study analytically the generalized quark--anti-quark potential
in the limit of large imaginary twist to all orders in perturbation theory. We
demonstrate how the QSC reduces in this case to a one-dimensional Schrodinger
equation. In the process we establish a link between the Q-functions and the
solution of the Bethe-Salpeter equation.Comment: 31 pages, 1 figure; v2: minor correcton
Internal symmetries and linear properties: Full-permutation distinguishers and improved collisions on Gimli
Gimli is a family of cryptographic primitives (both a hash function and an AEAD scheme) that has been selected for the second round of the NIST competition for standardizing new lightweight designs. The candidate Gimli is based on the permutation Gimli, which was presented at CHES 2017. In this paper, we study the security of both the permutation and the constructions that are based on it. We exploit the slow diffusion in Gimli and its internal symmetries to build, for the first time, a distinguisher on the full permutation of complexity 2^64. We also provide a practical distinguisher on 23 out of the full 24 rounds of Gimli that has been implemented. Next, we give (full state) collision and semi-free start collision attacks on Gimli-Hash, reaching, respectively, up to 12 and 18 rounds. On the practical side, we compute a collision on 8-round Gimli-Hash. In the quantum setting, these attacks reach 2 more rounds. Finally, we perform the first study of linear trails in Gimli, and we find a linear distinguisher on the full permutation
Cryptanalysis of MORUS
Item does not contain fulltextAdvances in Cryptology - ASIACRYPT 2018 - 24th International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, QLD, Australia, December 2-
New Attacks on the Concatenation and XOR Hash Combiners
We study the security of the concatenation combiner for two independent iterated hash functions with -bit outputs that are built using the Merkle-Damgård construction. In 2004 Joux showed that the concatenation combiner of hash functions with an -bit internal state does not offer better collision and preimage resistance compared to a single strong -bit hash function. On the other hand, the problem of devising second preimage attacks faster than against this combiner has remained open since 2005 when Kelsey and Schneier showed that a single Merkle-Damgård hash function does not offer optimal second preimage resistance for long messages.
In this paper, we develop new algorithms for cryptanalysis of hash combiners and use them to devise the first second preimage attack on the concatenation combiner. The attack finds second preimages faster than for messages longer than and has optimal complexity of . This shows that the concatenation of two Merkle-Damgård hash functions is not as strong a single ideal hash function.
Our methods are also applicable to other well-studied combiners, and we use them to devise a new preimage attack with complexity of on the XOR combiner of two Merkle-Damgård hash functions. This improves upon the attack by Leurent and Wang (presented at Eurocrypt 2015) whose complexity is (but unlike our attack is also applicable to HAIFA hash functions).
Our algorithms exploit properties of random mappings generated by fixing the message block input to the compression functions of and . Such random mappings have been widely used in cryptanalysis, but we exploit them in new ways to attack hash function combiners
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