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Distinguishing Attacks are a class of attacks on stream ciphers, which evaluate the random peroperties of the keystream generated by a stream cipher. In fact in these attacks the cryptanalyst tries to determine whether a stream is generated by a specific cipher or it seems random. Most of the Distinguishing attacks use the linear cryptanalysis technique and are called Linear Distinguishing Attack. The focus of this thesis is on linear distinguishing attacks. After a survey on stream ciphers and their cryptanalysis methods, distinguishing attack is introduced in detail. Then a new successful linear distinguishing attack on a recently developed stream cipher, Shannon, is presented. This attack... 

In this thesis, we analyze and compare switching and CPSP cryptography systems. CPSP is a dynamic system which can act as synchronized or self-synchronized stream cipher under specific conditions. To do the comparison, first we have a brief review of cryptography fundamentals like stream cipher systems, synchronized stream ciphers, and self-synchronized ones. Then, we consider chaos systems in general form and then we present their role in cryptography systems, and in continue by introducing switching cryptography systems and also CPSP cryptography systems, and analyzing their relation with self-synchronized stream ciphers, we do our statistical tests on them  

Stream ciphers are one of the cryptography primitives which have high speed in encryption process and less amount of hardware which they used. Guess and determine attacks are general attacks on stream ciphers which have often been implemented in ad hoc manner. Finding the minimal basis for internal state of a cryptosystem based on connection equations is the main challenge in stream ciphers. In recent years, some efforts for applying this attack in the systematic manner are started. First work in this area is the Simple Guess and Determine attack. The dvanced and Heuristic Guess and Determine attacks then presented, which all of them have heuristic structure. In this thesis, after reviewing... 

Stream ciphers are cryptographic schemes being widely used in communications as a means of providing security of data. Hence, scrutinizing their level of security against different cryptanalytic methods has obviously turned to be of great importance. Randomness of the keystream is an important requirement for stream ciphers. The cipher should be designed in such a way that the keystream is free of any statistical biases that would let attackers distinguish it from a random sequence. A distinguishing attack on a stream cipher is one that determines whether a given stream of symbols is a truly random sequence or generated by a specific cipher with an unknown key. In this thesis, we focus on... 

According to the development of communication, cryptography has become a vital issue. Several algorithms have been introduced for cryptography applications. Stream ciphers are such algorithms with high speed and appropriate efficiency. Lots of attacks have been applied to stream ciphers. We concentrate on two kinds of attacks in this thesis. Distinguishing attack is a general attack in which the attacker tries to distinguish the observed output sequence from random. Designers apply this kind of attack to test the statistical probabilities of the output sequence. We applied this attack on Grain family and Trivium family. In the proposed attack, nonlinear parts are replaced with linear ones.... 

The purpose of this dissertation is to investigate encryption of multimedia files using self-synchronizing stream ciphers. First, we will briefly examine various features of self-synchronizing stream ciphers, where we also review some self-synchronizing stream cipher design techniques. In particular, we study the system $ \mathbf{S}_{\sigma} ^ 4 $ (Daneshgar and Mohebbipour, $ 2018 $), which is designed using unknown input observer techniques. In Chapter~3, compression algorithms for $ JPEG $ and $ MPEG $ are discussed in detail. Finally, in Chapter~4, we briefly study some multimedia encryption algorithms that are used for $ JPEG $ and $ MPEG $ compression algorithms. The results of using...