181 research outputs found
Differential and invertibility properties of BLAKE (full version)
BLAKE is a hash function selected by NIST as one of the 14 second round candidates for the SHA-3 Competition. In this paper, we follow a bottom-up approach to exhibit properties of BLAKE and of its building blocks: based on differential properties of the internal function G, we show that a round of BLAKE is a permutation on the message space, and present an efficient inversion algorithm. For 1.5 rounds we present an algorithm that finds preimages faster than in previous attacks. Discovered properties lead us to describe large classes of impossible differentials for two rounds of BLAKE’s internal permutation, and particular impossible differentials for five and six rounds, respectively for BLAKE- 32 and BLAKE-64. Then, using a linear and rotation-free model, we describe near-collisions for four rounds of the compression function. Finally, we discuss the problem of establishing upper bounds on the probability of differential characteristics for BLAKE
Connections between the stability of a Poincare map and boundedness of certain associate sequences
Let and be two natural numbers and let be the -periodic discrete evolution family of matrices, having complex scalars as entries, generated by -valued, -periodic sequence of matrices We prove that the solution of the following discrete problem is bounded for each and each -vector if the Poincare map is stable. The converse statement is also true if we add a new assumption to the boundedness condition. This new assumption refers to the invertibility for each of the matrix By an example it is shown that the assumption on invertibility cannot be removed. Finally, a strong variant of Barbashin's type theorem is proved
A Dynamic Programming Solution to Bounded Dejittering Problems
We propose a dynamic programming solution to image dejittering problems with
bounded displacements and obtain efficient algorithms for the removal of line
jitter, line pixel jitter, and pixel jitter.Comment: The final publication is available at link.springer.co
Nonlinear software sensor for monitoring genetic regulation processes with noise and modeling errors
Nonlinear control techniques by means of a software sensor that are commonly
used in chemical engineering could be also applied to genetic regulation
processes. We provide here a realistic formulation of this procedure by
introducing an additive white Gaussian noise, which is usually found in
experimental data. Besides, we include model errors, meaning that we assume we
do not know the nonlinear regulation function of the process. In order to
illustrate this procedure, we employ the Goodwin dynamics of the concentrations
[B.C. Goodwin, Temporal Oscillations in Cells, (Academic Press, New York,
1963)] in the simple form recently applied to single gene systems and some
operon cases [H. De Jong, J. Comp. Biol. 9, 67 (2002)], which involves the
dynamics of the mRNA, given protein, and metabolite concentrations. Further, we
present results for a three gene case in co-regulated sets of transcription
units as they occur in prokaryotes. However, instead of considering their full
dynamics, we use only the data of the metabolites and a designed software
sensor. We also show, more generally, that it is possible to rebuild the
complete set of nonmeasured concentrations despite the uncertainties in the
regulation function or, even more, in the case of not knowing the mRNA
dynamics. In addition, the rebuilding of concentrations is not affected by the
perturbation due to the additive white Gaussian noise and also we managed to
filter the noisy output of the biological systemComment: 21 pages, 7 figures; also selected in vjbio of August 2005; this
version corrects a misorder in the last three references of the published
versio
Whitham's equations for modulated roll-waves in shallow flows
This paper is concerned with the detailed behaviour of roll-waves undergoing
a low-frequency perturbation. We rst derive the so-called Whitham's averaged
modulation equations and relate the well-posedness of this set of equations to
the spectral stability problem in the small Floquet-number limit. We then fully
validate such a system and in particular, we are able to construct solutions to
the shallow water equations in the neighbourhood of modulated roll-waves proles
that exist for asymptotically large time
Observability/Identifiability of Rigid Motion under Perspective Projection
The "visual motion" problem consists of estimating the motion of an object viewed under projection. In this paper we address the feasibility of such a problem.
We will show that the model which defines the visual motion problem for feature points in the euclidean 3D space lacks of both linear and local (weak) observability. The locally observable manifold is covered with three levels of lie differentiations. Indeed, by imposing metric constraints on the state-space, it is possible to reduce the set of indistinguishable states.
We will then analyze a model for visual motion estimation in terms of identification of an Exterior Differential System, with the parameters living on a topological manifold, called the "essential manifold", which includes explicitly in its definition the forementioned metric constraints. We will show that rigid motion is globally observable/identifiable under perspective projection with zero level of lie differentiation under some general position conditions. Such conditions hold when the viewer does not move on a quadric surface containing all the visible points
BlindHarmony: "Blind" Harmonization for MR Images via Flow model
In MRI, images of the same contrast (e.g., T) from the same subject can
exhibit noticeable differences when acquired using different hardware,
sequences, or scan parameters. These differences in images create a domain gap
that needs to be bridged by a step called image harmonization, to process the
images successfully using conventional or deep learning-based image analysis
(e.g., segmentation). Several methods, including deep learning-based
approaches, have been proposed to achieve image harmonization. However, they
often require datasets from multiple domains for deep learning training and may
still be unsuccessful when applied to images from unseen domains. To address
this limitation, we propose a novel concept called `Blind Harmonization', which
utilizes only target domain data for training but still has the capability to
harmonize images from unseen domains. For the implementation of blind
harmonization, we developed BlindHarmony using an unconditional flow model
trained on target domain data. The harmonized image is optimized to have a
correlation with the input source domain image while ensuring that the latent
vector of the flow model is close to the center of the Gaussian distribution.
BlindHarmony was evaluated on both simulated and real datasets and compared to
conventional methods. BlindHarmony demonstrated noticeable performance on both
datasets, highlighting its potential for future use in clinical settings. The
source code is available at: https://github.com/SNU-LIST/BlindHarmonyComment: ICCV 2023 accepted. 9 pages and 5 Figures for manuscipt,
supplementary include
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