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Search Results: 1 - 10 of 67 matches for " Keijo Haataja "
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Novel Hybrid Encryption Algorithm Based on Aes, RSA, and Twofish for Bluetooth Encryption  [PDF]
Marwan Ali Albahar, Olayemi Olawumi, Keijo Haataja, Pekka Toivanen
Journal of Information Security (JIS) , 2018, DOI: 10.4236/jis.2018.92012
In this paper, we proposed a novel triple algorithm based on RSA (Rivest-Shamir-Adleman), AES (Advanced Encryption Standard), and TwoFish in order to further improve the security of Bluetooth that is currently using only 128-bit AES for encryption in its latest versions (Bluetooth 4.0 - 5.0). Further-more, older Bluetooth 1.0A – 3.0 + HS (High-Speed) devices use E0 stream cipher for encryption that has been shown to be weak by numerous researchers and thus it could be considered insufficient for high security purposes nowadays. In our novel approach, the triple protection of AES, RSA, and TWOFISH would enhance the level of security, which shields the data transmission in the Bluetooth. As the first step of our novel approach, we first encrypted the message by using AES with 128-bit key and then further encrypted it by using Twofish with the same 128-bit key. Finally, the 128-bit key generated in the beginning will be encrypted by using RSA with 1024-bit key to protect its over-the-air transfer. In the receiving end, the decryption process goes in reverse order compared with encryption process. We showed with experimental figures that our novel algorithm improved the security of Bluetooth encryption by eliminating all known weaknesses and thus made data exchange between Bluetooth devices secure.
Meaningful Academic Work as Praxis in Emergence
Keijo R?s?nen
Journal of Research Practice , 2008,
Abstract: The managerial form of university governance has changed the conditions of academic work in many countries. While some academics consider this a welcome development, others experience it as a threat to their autonomy and to the meaningfulness of their work. This essay suggests a stance in response to the current conditions that should serve especially the latter group of academics. The claim is that by approaching academic work as a potential praxis in emergence, it is possible to appreciate local, autonomous activity in renewing academic work. Even if such efforts remain difficult, dispersed in space, discontinuous in time, and incomplete, they may provide a sense of direction and keep up hope. The conception of praxis is a way of articulating the mission of such efforts; simultaneously, it is also a way of defining an epistemic object for research on academic work.
Algebraic independence of certain Mahler numbers
Keijo V??n?nen
Mathematics , 2015,
Abstract: In this note we prove algebraic independence results for the values of a special class of Mahler functions. In particular, the generating functions of Thue-Morse, regular paperfolding and Cantor sequences belong to this class, and we obtain the algebraic independence of the values of these functions at every non-zero algebraic point in the open unit disk. The proof uses results on Mahler's method.
Proceedings 10th International Workshop on Parallel and Distributed Methods in verifiCation
Ji?í Barnat,Keijo Heljanko
Computer Science , 2011, DOI: 10.4204/EPTCS.72
Abstract: This volume contains the proceedings of the 10th International Workshop on Parallel and Distributed Methods in verifiCation (PDMC 2011) that took place in Snowbird, Utah, on July 14, 2011. The workshop was co-located with 23rd International Conference on Computer Aided Verification (CAV 2011). The PDMC workshop series covers all aspects related to the verification and analysis of very large and complex systems using, in particular, methods and techniques that exploit contemporary, hence parallel, hardware architectures. To celebrate the 10th anniversary of PDMC, the workshop consisted of a half day invited session together and a half day session of regular contributed presentations.
Bounded LTL Model Checking with Stable Models
Keijo Heljanko,Ilkka Niemel?
Computer Science , 2003,
Abstract: In this paper bounded model checking of asynchronous concurrent systems is introduced as a promising application area for answer set programming. As the model of asynchronous systems a generalisation of communicating automata, 1-safe Petri nets, are used. It is shown how a 1-safe Petri net and a requirement on the behaviour of the net can be translated into a logic program such that the bounded model checking problem for the net can be solved by computing stable models of the corresponding program. The use of the stable model semantics leads to compact encodings of bounded reachability and deadlock detection tasks as well as the more general problem of bounded model checking of linear temporal logic. Correctness proofs of the devised translations are given, and some experimental results using the translation and the Smodels system are presented.
On the degree of a Kloosterman sum as an algebraic integer
Keijo Kononen,Marko Rinta-aho,Keijo V??n?nen
Mathematics , 2011,
Abstract: The maximal degree over rational numbers that an n-dimensinonal Kloosterman sum defined over a finite field of characteristic p can achieve is known to be (p-1)/d where d=gcd(p-1,n+1). Wan has shown that this maximal degree is always achieved in points whose absolute trace is nonzero. By the works of Fischer, Wan we know that there exist many finite fields for which the values of the Kloosterman sums are distinct except Frobenius conjugation. For these fields we completely determine the degrees of all the Kloosterman sums. Even if the finite field does not satisfy this condition we can still often find points in which the Kloosterman sum has smaller degree than (p-1)/d.
Use of flow cytometry for the adhesion analysis of Streptococcus pyogenes mutant strains to epithelial cells: investigation of the possible role of surface pullulanase and cysteine protease, and the transcriptional regulator Rgg
Jukka Hyt?nen, Sauli Haataja, Jukka Finne
BMC Microbiology , 2006, DOI: 10.1186/1471-2180-6-18
Abstract: Streptococcal mutants were readily labelled with CFDA-SE and their binding to epithelial cells could be effectively studied by flow cytometry. A strain deficient in Rgg expression showed increased binding to the analyzed epithelial cell lines of various origin. Inactivation of SpeB had no effect on the adhesion, while PulA knock-out strains displayed decreased binding to the cell lines.These results suggest that the flow cytometric assay is a valuable tool in the analysis of S. pyogenes adherence to host cells. It appears to be an efficient and sensitive tool for the characterization of interactions between the bacteria and the host at the molecular level. The results also suggest a role for Rgg regulated surface molecules, like PulA, in the adhesion of S. pyogenes to host cells.Flow cytometry has been established as a standard tool in the characterization of eukaryote cells and their interactions. Flow cytometric adherence assay has in recent years also been adopted for the analysis of interactions between bacteria and eukaryotic cells [1,2]. The results suggest some benefits over conventional assays but the method has not yet been much used. In conventional adherence assays, bacteria are allowed to attach to solid-phase immobilized cells, and after washings, released by lysing the host cells and enumerated either by time-consuming plate cultures or by counting the bacteria using a microscope. In contrast, the flow cytometric assay displays characteristics such as fast performance, large through-put of analyzed cells, and the avoidance of washing steps. This should allow even the detection of weak interactions between bacteria and host cells. In addition, since the bacteria and host cells interact in liquid phase, other types of bacterium-cell interactions may take place as compared to solid-phase assays. On the other hand, mechanical detachment of the cell for flow cytometry based adhesion assay may in theory create artificial binding activities, which are avoided
Crossover Scaling of Wavelength Selection in Directional Solidification of Binary Alloys
Michael Greenwood,Mikko Haataja,Nikolas Provatas
Physics , 2004, DOI: 10.1103/PhysRevLett.93.246101
Abstract: We simulate dendritic growth in directional solidification in dilute binary alloys using a phase-field model solved with an adaptive-mesh refinement. The spacing of primary branches is examined for a range of thermal gradients and alloy compositions and is found to undergo a maximum as a function of pulling velocity, in agreement with experimental observations. We demonstrate that wavelength selection is unambiguously described by a non-trivial crossover scaling function from the emergence of cellular growth to the onset of dendritic fingers, a result validated using published experimental data.
Phase-field Crystals with Elastic Interactions
Peter Stefanovic,Mikko Haataja,Nikolas Provatas
Physics , 2006, DOI: 10.1103/PhysRevLett.96.225504
Abstract: We report on a novel extension of the recent phase-field crystal (PFC) method introduced in [Elder et al., Phys. Rev. Lett., Vol. 88, 245701:1-4 (2002)], which incorporates elastic interactions as well as crystal plasticity and diffusive dynamics. In our model, elastic interactions are mediated through wave modes that propagate on time scales many orders of magnitude slower than atomic vibrations but still much faster than diffusive times scales. This allows us to preserve the quintessential advantage of the PFC model: the ability to simulate atomic-scale interactions and dynamics on time scales many orders of magnitude longer than characteristic vibrational time scales. We demonstrate the two different modes of propagation in our model and show that simulations of grain growth and elasto-plastic deformation are consistent with the microstructural properties of nanocrystals.
Linear Independence of -Logarithms over the Eisenstein Integers
Peter Bundschuh,Keijo V??n?nen
International Journal of Mathematics and Mathematical Sciences , 2010, DOI: 10.1155/2010/839695
Abstract: For fixed complex with , the -logarithm is the meromorphic continuation of the series , into the whole complex plane. If is an algebraic number field, one may ask if are linearly independent over for satisfying . In 2004, Tachiya showed that this is true in the Subcase , , , and the present authors extended this result to arbitrary integer from an imaginary quadratic number field , and provided a quantitative version. In this paper, the earlier method, in particular its arithmetical part, is further developed to answer the above question in the affirmative if is the Eisenstein number field , an integer from , and a primitive third root of unity. Under these conditions, the linear independence holds also for , and both results are quantitative. 1. Introduction and Results For fixed complex of absolute value greater than 1, the -logarithm is defined by the power series which converges in and has the meromorphic continuation into the whole complex plane. In the early 1990s, the irrationality investigations on this -logarithm got a fresh impetus by two papers of Borwein [1, 2], where he introduced new analytic tools to demonstrate quantitative versions of the following. If and if , then both numbers and are irrational, with the second result appearing only in [2]. The next important step was made by Tachiya [3], who succeeded in proving, for , the linear independence of over using Borwein's function theoretic method from [2]. Shortly later, quantitative refinements of this result and also of the linear independence of were obtained independently by Zudilin [4] and by the present authors [5]; here the dash indicates differentiation with respect to . Somehow related to Tachiya's above-mentioned theorem is the linear independence over of for squares , which was established in [6]. Another result, proved in [7], is the linear independence of for any . It should be noted that all these linear independence statements remain true if one replaces by an arbitrary imaginary quadratic number field and if one supposes to be in its ring of integers. One starting point of our present work was the question whether we can replace in Tachiya's result the primitive second root of unity ( , of course) by a primitive third root of unity. As we will see in Theorem 1.2 below, this is indeed true if we study linear independence over the particular quadratic number field . The parameter has to be from its ring of integers, which is sometimes called ring of Eisenstein integers since Eisenstein (1844) was the first to thoroughly investigate its algebraic properties in the course of
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