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The prediction and probability assignment (PPA) concept is important in lossless image compression. We report on a new approximate technique for PPA based on local optimization.
A new message authentication code (MAC) is described that exploits the tree structure present in many modern document formats, e.g. SGML and XML. The new code supports incremental updating of the cryptographic checksum in the process of making incremental changes to the document. Theoretical bounds on the probability of a successful substitution attack are derived. Through experimental results we
Message authentication codes (MACs) using polynomial evaluation have the advantage of requiring a very short key even for very large messages. We describe a low complexity software polynomial evaluation procedure, that for large message sizes gives a MAC that has about the same low software complexity as for bucket hashing but requires only small keys and has better security characteristics.
The verification of the authenticity of a text document or a datafile is one of the main applications of cryptographic techniques. A common used technique for this purpose is the application of a message authentication code (MAC). Usually the MAC computation has to be done in software. Based on the relationship between error-correcting codes and so-called families of almost universal hash function
Some of the best compression ratios for text compression are provided by the PPM (prediction by partial matching) class of algorithms. These algorithms are based on arithmetic coding using a fixed-depth Markov chain model of the source, i.e., the subsequence of symbols generated in any state s of the source is assumed to be the output of a memoryless subsource w=w(s). One of the most crucial steps
We present a coding theoretic approach to the problem the initial state recovery of a linear feedback shift register when a noisy output sequence is given. Our work is focused on the investigation of the asymptotical behaviour of the recovery process. We give two algorithms which will work for shift registers with arbitrary feedback polynomial. Furthermore, the number of required given noisy symbo
We present an analysis of some known cartesian authentication codes and their modification into authentication codes with secrecy, with transmission rate R = r/n, where n = 2, 3, …, and 1 ≤ r ≤ n - 1 using (n - r)(r + 1) q-ary key digits. For this purpose we use a grouping technique. Essentially the same key grouping technique is used for the construction of codes that withstand spoofing attacks o
Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in their local gas environment, and the dynamics of the response is a decisive factor for the catalysts’ action and activity. Few probes are able to map catalyst structure and local gas environment simultaneously under reaction conditions at the timescales of the dynamic changes. Here we use the CO oxidation react
Scaling down material synthesis to crystalline structures only few atoms in size and precisely positioned in device configurations remains highly challenging, but is crucial for new applications e.g., in quantum computing. We propose to use the sidewall facets of larger III–V semiconductor nanowires (NWs), with controllable axial stacking of different crystal phases, as templates for site-selectiv
Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this articl
”Conflict in Colours” är en avhandling som fokuserar på historiska narrativs roll i att legitimera och bibehålla konflikter, samt hur dessa narrativ påverkar den begynnande fredsprocessen. Genom att studera det inneboende kulturella våldet i dessa narrativ har jag visat hur kulturellt våld är en essentiell del i att legitimera, påverka och bibehålla det antagonistiska förhållandet mellan parterna Conflict in Colours is a book about the role of cultural violence in maintaining and transferring conflict situations by investigating republican and loyalist murals in Belfast during the Troubles and the Northern Irish peace process. During several decades, the people of Northern Ireland have endured warlike situations before the peace agreement in 1998. This doctoral thesis examines the ways/how
The effect of two different pair correlation functions, used to model multiple scattering in a slab filled with randomly located spherical particles, is investigated. Specifically, the Percus-Yevick approximation is employed and a comparison with the simple hole correction is made. The kernel entries of the hole correction have an analytic solution, which makes the numerical solution of the integr
Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10–100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we inv
Specific heat and small-angle neutron scattering measurements have been performed on the superconductor β-PdBi2. Whereas models with a uniform gap do not yield an adequate description of the temperature-dependent specific heat and the temperature and magnetic field dependence of the SANS intensity, fits to a heuristic model with two gap parameters agree well with both data sets. The fact that two
