154 research outputs found
PROBLEM SOLVING SUPPORT BY THE MULTI-LAYER HYPERMEDIA MODEL
Hypermedia is a suitable tool to describe knowledge and to support the
problem solving process. Hypermedia nodes contain information elements and
links represent relations between them. The users of present electronic
materials, however, cannot modify the contents of the materials and include
their individual knowledge. A new hypertext model, called Multi-Layer
Hypermedia Model (MLHM) was developed to support the manipulation of the
presented knowledge. With applying this model, electronic materials can be
created that express writer´s as well as user´s knowledge and support the
problem solving process. When using HTML as the basic layer of the model,
the hypermedia system can expand the usability of HTML based materials
TESTING THE OPERATION OF HIGH Tc SUPERCONDUCTING FAULT CURRENT LIMITER IN A REAL SYSTEM
This paper presents the effects of an inductive type
high-temperature superconducting fault current limiter (HTS FCL) on a
three-phase system have been investigated both theoretically and experimentally
in the case of a shunt and a subsequent series fault.
Calculations have been performed for different cases including those when
currents in the faultless phases would increase. This may lead to an incorrect
operation of the automatic protection elements even in the faultless phases.
The calculations based on the method of symmetrical components.
To investigate the real physical processes, a measuring instrument was
constructed to measure the transients due to the fast acting HTS FCL
On the Security of Data Markets and Private Function Evaluation
The income of companies working on data markets steadily grows year by year. Private function evaluation (PFE) is a valuable tool in solving corresponding security problems. The task of Controlled Private Function Evaluation and its relaxed version was introduced in [Horvath et.al., 2019]. In this article, we propose and examine several different approaches for such tasks with computational and information theoretical security against static corruption adversary. The latter level of security implies quantum-security. We also build known techniques and constructions into our solution where they fit into our tasks. The main cryptographic primitive, naturally related to the task is 1-out-of-n oblivious transfer. We use Secure Multiparty Computation techniques and in one of the constructions functional encryption primitive. The analysis of the computational complexity of the constructions shows that the considered tasks can efficiently be implemented, however it depends on the range of parameter values (e.g. size of database, size of the set of permitted function), the execution environment (e.g. concurrency) and of course on the level of security
New look at impossibility result on Dolev-Yao models with hashes
Backes, Pfitzmann and Waidner showed in [7] that for protocols with hashes Dolev-Yao style models do not have cryptographically sound realization in the sense of BRSIM/UC in the standard model of cryptography. They proved that random oracle model provides a cryptographically sound realization. Canetti [9] introduced the notion of oracle hashing “towards realizing random oracles”. Based on these two approaches, we propose a random hash primitive, which already makes possible cryptographically sound realization in the sense of BRSIM/UC in the standard model of cryptography
Non-malleable public key encryption in BRSIM/UC
We propose an extension to the BRSIM/UC library of Backes, Pfitzmann and Waidner [1] with non-malleable public key encryption. We also investigate the requirement of “full randomization” of public key encryption primitives in [1], and show that additional randomization to attain word uniqueness is theoretically not justified
Növekedésoptimális portfólió elmélet
A dolgozat alapproblĂ©mája a vĂ©gtelen idĹ‘ horizonton valĂł optimális befektetĂ©si politika vizsgálata. A kĂ©rdĂ©sen számos neves közgazdász dolgozott, mĂ©g Merton Ă©s Samuelson figyelmĂ©t is felkeltettĂ©k a kutatások. A disszertáciĂłban szekvenciális befektetĂ©si (portfĂłliĂł-választási) stratĂ©giákat mutatunk be. Szekvenciális stratĂ©gia alatt, olyan kauzális stratĂ©giát Ă©rtĂĽnk, amely a piacrĂłl rendelkezĂ©sre állĂł mĂşltbeli adatokat használva, minden kereskedĂ©si periĂłdus (nap) elejĂ©n megváltoztathatja a portfĂłliĂłt, azaz a tĹ‘kĂ©t Ăşjraoszthatja a rendelkezĂ©sre állĂł Ă©rtĂ©kpapĂrok között. A vĂ©gtelen idĹ‘horizonton valĂł optimális befektetĂ©s problĂ©májának vizsgálata során elĹ‘ször azt kell tisztázni, hogy mit is Ă©rtĂĽnk egyáltalán az optimális szĂłn. A dolgozat cĂmĂ©ben jelzett kutatási irány az optimalitás kritĂ©riumán a maximális átlagos növekedĂ©si ĂĽtemet Ă©rti vĂ©gtelenben vett határĂ©rtĂ©k Ă©rtelmĂ©ben. A befektetĹ‘ cĂ©lja, hogy hosszĂştávon maximalizálja a vagyonát anĂ©lkĂĽl, hogy ismernĂ© a rĂ©szvĂ©nyárfolyamokat generálĂł háttĂ©rfolyamat eloszlását. Szemben a klasszikus modellekkel, amelyek a piac működĂ©sĂ©nek a leĂrására erĹ‘s statisztikai feltĂ©telezĂ©seket tesznek, modellekben a matematikai vizsgálatok során használt egyetlen feltĂ©tel, hogy a napi hozamok stacionárius Ă©s ergodikus folyamatot alkotnak. E feltĂ©tel mellett az aszimptotikus növekedĂ©si rátának egy jĂłl definiált maximuma van, amely elĂ©rhetĹ‘ a teljes folyamateloszlásának ismeretĂ©ben az Ăşgynevezett log-optimális portfĂłliĂł alkalmazásával. A log-optimális stratĂ©gia optimalitása azt jelenti, hogy egyetlen másik stratĂ©gia sem produkál a vĂ©gtelen idĹ‘horizonton nagyobb átlagos növekedĂ©si ĂĽtemet. A disszertáciĂł fĹ‘bb megválaszolandĂł kĂ©rdĂ©sei a következĹ‘k. • Hogyan approximálni a log-optimális portfĂłliĂłt egy kisebb számĂtási költsĂ©gű algoritmus segĂtsĂ©gĂ©vel? • Mi a kapcsolat a log-optimális Ă©s a Markowitz portfĂłliĂł stratĂ©gia között? • Hogyan lehet termĂ©szetesen bevezetni kockázat kontrollt a log-optimális elmĂ©letbe? Melyek a kockázat megszorĂtás melletti log-optimális portfĂłliĂł aszimptotikus tulajdonságai? • Hogyan konstruálhatĂł meg a szemi-log-optimális portfĂłliĂł Ă©s a Markowitz-tĂpusĂş portfĂłliĂł empirikus változata? • Mi az egy-valĂłszĂnűsĂ©ggel optimális portfĂłliĂł diszkrĂ©t idejű Markov hozamfolyamat Ă©s arányos tranzakciĂłs költsĂ©g esetĂ©n
Cryptographically Sound Security Proof for On-Demand Source Routing Protocol EndairA
We present the first cryptographically sound security proof of a routing protocol for mobile ad-hoc networks. More precisely, we show that the route discovery protocol does not output a non-existing path under arbitrary active attacks, where on a non-existing path there exists at least one pair of neighboring nodes without communication connection during the run of the route discovery protocol. The proof relies on the Dolev-Yao-style model of Backes, Pfitzmann and Waidner, which allows for mapping results obtained symbolically within this model to cryptographically sound proofs if certain assumptions are met
On Central Bank Digital Currency: A composable treatment
Central Bank Digital Currency (CBDC) is in the phase of discussion in most of countries. In this paper, we consider the security issues of centralized retail CBDC. Our focus is on the design and analysis of the underlying cryptographic protocol. The main security requirements against the protocol are transaction anonymity and protection against tax evasion. The protocol provides security guarantees in case of the strongest model of an execution environment which is the general concurrent environment. We apply the Universal Composition (UC) methodology of Canetti [3],[4]. At the time of this writing, we are not aware of any published CBDC protocol with an aim to provide secure compositional guarantees
The UC approach: an application view
What kind of guidelines can the UC approach provide for traditional designs and applications? The aim of this report is to bring this theoretically rooted, computer scientist technology closer to the community of practitioners in the field of protocol designs
- …