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Gebze, Turkey

Ustuner F.,Tubitak BILGEM UEKAE
Progress in Electromagnetics Research Symposium | Year: 2011

The safety distance concept is widely used in the installation of cellular base stations to define a radiation hazard zone around the periphery of the base station. In this paper, three dimensional safety distance analysis around a specific cellular base station is carried out using ray optic techniques with the diffraction theory included. The calculated electric field equivalent to health limit is plotted in a contour line form to illustrate the safety distance around the base station. The resulting plots illustrate the radiation hazard areas.

Yildirim A.,Tubitak BILGEM UEKAE
IET Signal Processing | Year: 2011

The author analyses the target range estimation errors in pulse compression high-resolution radars (HRRs). Conventional radar signal processors assume a point target model in matched filtering-based detection and tracking. The author demonstrates through simulations that the performance degradation, under the point target assumption, can be significant for HRRs, where targets extend across several detection cells. Also, the author models events of backscatters from illuminated target and clutter as a non-homogenous Poisson process (NHPP). The corresponding maximum likelihood, maximum a posteriori, minimum mean square error and minimum mean absolute error estimators are derived for range estimation. Typical target detection process has been simulated and the performance of NHPP-based estimators has been compared to that of the most commonly used peak estimators, namely, the maximum point and interpolation peak estimators. Simulation results show that the proposed estimators significantly reduce target range estimation errors in HRRs. © 2011 The Institution of Engineering and Technology.

Boztas O.,Tubitak BILGEM UEKAE | Boztas O.,Middle East Technical University | Karakoc F.,Tubitak BILGEM UEKAE | Karakoc F.,Technical University of Istanbul | And 2 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

TWINE is a lightweight block cipher designed for multiple platforms and was proposed at Selected Areas in Cryptography, 2012. The number of rounds of TWINE is 36 and the most powerful attack given by the designers is the impossible differential attack against 24 rounds of TWINE-128 whose time complexity is 2115.10 encryptions and data complexity is 252.21 blocks. The best attack known so far is the biclique attack on the full round cipher with a time complexity of 2126.82 and data complexity of 2 60. However the time complexity of biclique attack is near exhaustive search and data needed for the attack is near the whole codebook. In this paper we propose some meet-in-the-middle type attacks on reduced round TWINE-128. We show that meet-in-the-middle type attacks can be applied on more rounds than the best attack done by the designers while they claim that the first 5 rounds contain all the key bits for TWINE-128. Our attacks are due to the slow diffusion of both the cipher and the key schedule algorithm. One of our attacks just use 212 chosen plaintext-ciphertext pair with time complexity of 2124 to break 21 rounds of the algorithm. Also we propose another attack on 25 rounds of the cipher by using 248 chosen plaintext-ciphertext pairs with the time complexity of 2122 and memory complexity of 2125 while the best attack proposed by the designers is for 24 rounds. © 2013 Springer-Verlag.

Ozturk Y.,Tubitak BILGEM UEKAE | Ozturk Y.,Gebze Institute of Technology | Ustuner F.,Tubitak BILGEM UEKAE
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011 | Year: 2011

Determination of the radiation pattern is one of the major issues in antenna characterization. Radiation pattern is a far field parameter and it must be measured at a point where wave trains are propagating in same phase. Although this range can be obtained inside a laboratory for isotropic antennas, in case of high gain directive antennas it can well extend to several tens of meters. Radiation pattern measurement using near field approach is possible for the latter case, even inside a small-scale laboratory. Nevertheless, since the design and the realization of near field antenna measurement systems require detailed engineering activities compared to that of far field systems, their costs are fairly high. In order to obtain a low-cost, maintainable and native near field antenna measurement system, an engineering study was conducted in TUBITAK BILGEM UEKAE EMC Laboratory and a near field measurement system was developed. In this article, antenna patterns measured by the developed system are presented. © 2011 IEEE.

Karakoc F.,Tubitak BILGEM UEKAE | Karakoc F.,Technical University of Istanbul | Demirci H.,Tubitak BILGEM UEKAE | HarmancI A.E.,Technical University of Istanbul
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

In this paper we analyze the security of PRINTcipher using a technique that combines differential and linear cryptanalysis. This technique is different from differential-linear cryptanalysis. We use linear approximations to increase the probability of differential characteristics. We show that specific choices of some of the key bits give rise to a certain differential characteristic probability, which is far higher than the best characteristic probability claimed by the designers. We give the underlying mechanism of this probability increase. We have developed attacks on 29 and 31 rounds of PRINTcipher-48 for 4.54% and 0.036% of the keys, respectively. Moreover, we have implemented the proposed attack algorithm on 20 rounds of the cipher. © 2012 Springer-Verlag.

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