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Yayın Comment on "Modified Baptista type chaotic cryptosystem via matrix secret key" [Phys. Lett. A 372 (2008) 5427](Elsevier Science BV, 2009-09-07) Rhouma, Rhouma; Solak, Ercan; Arroyo, David; Li, Shujun; Alvarez, Gonzalo; Belghith, Safya MdimeghIn this comment, we analyze a recently proposed Baptista-like cryptosystem and show that it is not invertible. Others weaknesses are also reported. A modified version of this cryptosystem is proposed to show how to overcome the non-invertibility.Yayın Cryptanalysis of a multi-chaotic systems based image cryptosystem(Elsevier Science BV, 2010-01-15) Solak, Ercan; Rhouma, Rhouma; Belghith, Safya MdimeghThis paper is a cryptanalysis of a recently proposed multi-chaotic systems based image cryptosystem. The cryptosystem is composed of two shuffling stages parameterized by chaotically generated sequences. We propose and implement two different attacks which completely break this encryption scheme.Yayın A hybrid approach to private record matching(IEEE Computer Soc, 2012-10) İnan, Ali; Kantarcıoğlu, Murat; Ghinita, Gabriel; Bertino, ElisaReal-world entities are not always represented by the same set of features in different data sets. Therefore, matching records of the same real-world entity distributed across these data sets is a challenging task. If the data sets contain private information, the problem becomes even more difficult. Existing solutions to this problem generally follow two approaches: sanitization techniques and cryptographic techniques. We propose a hybrid technique that combines these two approaches and enables users to trade off between privacy, accuracy, and cost. Our main contribution is the use of a blocking phase that operates over sanitized data to filter out in a privacy-preserving manner pairs of records that do not satisfy the matching condition. We also provide a formal definition of privacy and prove that the participants of our protocols learn nothing other than their share of the result and what can be inferred from their share of the result, their input and sanitized views of the input data sets (which are considered public information). Our method incurs considerably lower costs than cryptographic techniques and yields significantly more accurate matching results compared to sanitization techniques, even when privacy requirements are high.Yayın Cryptanalysis of Fridrich's chaotic image encryption(World Scientific Publishing, 2010-05) Solak, Ercan; Çokal, Cahit; Yıldız, Olcay Taner; Bıyıkoğlu, TürkerWe cryptanalyze Fridrich's chaotic image encryption algorithm. We show that the algebraic weaknesses of the algorithm make it vulnerable against chosen-ciphertext attacks. We propose an attack that reveals the secret permutation that is used to shuffle the pixels of a round input. We demonstrate the effectiveness of our attack with examples and simulation results. We also show that our proposed attack can be generalized to other well-known chaotic image encryption algorithms.Yayın Breaking an orbit-based symmetric cryptosystem(Pergamon-Elsevier Science Ltd, 2011-09) Solak, Ercan; Rhouma, Rhouma; Belghith, Safya MdimeghWe report a break for a recently proposed class of cryptosystems. The cryptosystem uses constant points of a periodic secret orbit to encrypt the plaintext. In order to break the system, it suffices to sort the constant points and find the initial fixed point. We also report breaks for modified versions of the cryptosystem. In addition, we discuss some efficiency issues of the cryptosystem.Yayın Cryptanalysis of a cryptosystem based on discretized two-dimensional chaotic maps(Elsevier Science BV, 2008-11-17) Solak, Ercan; Çokal, CahitRecently, an encryption algorithm based on two-dimensional discretized chaotic maps was proposed [Xiang et al., Phys. Lett. A 364 (2007) 252]. In this Letter, we analyze the security weaknesses of the proposal. Using the algebraic dependencies among system parameters. we show that its effective key space can be shrunk. We demonstrate a chosen-ciphertext attack that reveals a portion of the key.Yayın Implementing lightweight, dynamic hierarchical key assignment scheme for cloud computing(IEEE, 2024-03-25) Çelikbilek, İbrahim; Çeliktaş, Barış; Özdemir, EnverIn this paper, we propose the implementation and adaptation of a hierarchical key assignment scheme (HKAS) previously developed in our research to improve access control in cloud computing environments. The secret keys generated and managed by this scheme can be utilized for various purposes within the cloud computing, including data encryption, integrity checks, secure communications, and accessing critical infrastructures or services. Our implementation performs dynamic update operations with minimal computational cost and storage demands, as users within the hierarchical structure do not store any key components. Through security analysis, the scheme demonstrates strong key indistinguishability security (S-KI-security), effectively safeguarding keys against various cryptographic attacks. The scheme's flexibility allows it to be tailored to specific organizational needs, whether for securing sensitive data, ensuring compliance with regulatory standards, or facilitating secure data sharing and collaboration in cloud environments. Thus, we advocate for the practical implementation of the HKAS in transitioning to cloud environments.Yayın Cryptanalysis of a chaos-based image encryption algorithm(Elsevier Science BV, 2009-03-30) Çokal, Cahit; Solak, ErcanA chaos-based image encryption algorithm was proposed in [Z.-H. Guan, F. Huang, W. Guan, Phys. Lett. A 346 (2005) 153]. In this Letter, we analyze the security weaknesses of the proposal. By applying chosen-plaintext and known-plaintext attacks, we show that all the secret parameters can be revealed.Yayın Generating multi-atom entangled W states via light-matter interface based fusion mechanism(Nature Publishing Group, 2015-11-09) Özaydın, Fatih; Zang, Xue-Ping; Yang, Ming; Song, Wei; Cao, Zhuo-LiangW state is a key resource in quantum communication. Fusion technology has been proven to be a good candidate for preparing a large-size W state from two or more small-size W states in linear optical system. It is of great importance to study how to fuse W states via light-matter interface. Here we show that it is possible to prepare large-size W-state networks using a fusion mechanism in cavity QED system. The detuned interaction between three atoms and a vacuum cavity mode constitute the main fusion mechanism, based on which two or three small-size atomic W states can be fused into a larger-size W state. If no excitation is detected from those three atoms, the remaining atoms are still in the product of two or three new W states, which can be re-fused. The complicated Fredkin gate used in the previous fusion schemes is avoided here. W states of size 2 can be fused as well. The feasibility analysis shows that our fusion processes maybe implementable with the current technology. Our results demonstrate how the light-matter interaction based fusion mechanism can be realized, and may become the starting point for the fusion of multipartite entanglement in cavity QED system.Yayın SIMSec: A key exchange protocol between SIM card and service provider(Springer New York LLC, 2016-08-01) Ok, Kerem; Coşkun, Vedat; Yarman, Bekir Sıddık Binboğa; Çevikbaş, Cem; Özdenizci Köse, BüşraMobile technology is so popular and overdosed adoption is inevitable in today’s world. As the mobile technologies have advanced, Service Providers (SP) have offered services via Smartphones and some of them required secure data communication between the Subscriber Identity Module (SIM) cards on Smartphones and the servers of SP. The latest SIM cards comply with recent specifications including secure domain generation, mobile signatures, pre-installed encryption keys, and other useful security services. Nevertheless, un-keyed SIM cards do not satisfy such requirements, thus end-to-end encryption between the SIM card and SP cannot be provided. In this paper, we provide a key exchange protocol, which creates a symmetric key through the collaborative work of the SIM card and the SP server. After a successful protocol performance, the SIM card and SP can perform end-to-end data encryption. After defining the protocol, we also discuss the security issues and provide a formal security analysis of the protocol using the Casper/FDR tool.
