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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 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 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 Kaotik kriptografinin çilesi(IEEE, 2013-06-13) Solak, ErcanSon yirmi yıldır araştırılan bir konu olmasına rağmen, kaotik kriptografi ana akım kriptografi literatüründe yer almıyor. Bu makalede, bu ayrımın nedenleri üzerinde durulmuştur.Yayın Algebraic break of a cryptosystem based on discretized two-dimensional chaotic maps(Elsevier Science BV, 2009-03-30) Solak, Ercan; Çokal, CahitRecently, a cryptosystem based on two-dimensional discretized chaotic maps was proposed [T. Xiang, et al., Phys. Lett. A 364 (2007) 252]. In this Letter, we cryptanalyze the proposal using algebraic methods. We give three different attacks that yield all the secret parameters of the cryptosystem.Yayın Cryptanalysis of image encryption with compound chaotic sequence(IEEE, 2009) Solak, ErcanRecently, an image encryption algorithm based on compound chaotic sequence was proposed [Tong et al., Image and Vision Computing 26 (2008) 843]. In this paper, we analyze the security weaknesses of the proposal. We give chosen-plaintext and known-plaintext attacks that yield the secret parameters of the algoritm. Our simulation results show that the computational complexity of the attacks is quite low.
