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31
New Approaches to the Design of SelfSynchronizing Stream Ciphers
 EUROCRYPT'91
, 1991
"... Selfsynchronizing stream ciphers (SSSC) are a commonly used encryption technique for channels with low bit error rate but for which bit synchronization can present a problem. Most presently used such ciphers are based on a block cipher (e.g. DES) in 1bit cipher feedback mode. In this paper, severa ..."
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Cited by 28 (0 self)
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Selfsynchronizing stream ciphers (SSSC) are a commonly used encryption technique for channels with low bit error rate but for which bit synchronization can present a problem. Most presently used such ciphers are based on a block cipher (e.g. DES) in 1bit cipher feedback mode. In this paper, several alternative design approaches for SSSCs are proposed that are superior to the design based on a block cipher with respect to encryption speed and potentially also with respect to security. A method for combining several SSSCs is presented that allows to prove that the combined SSSC is at least as secure as any of the component ciphers. The problem of designing SSSCs is contrasted with the problem of designing conventional synchronous additive stream ciphers and it is shown that different security criteria must be applied. Furthermore, an efficient algorithm is presented for finding a function of low degree that approximates a given Boolean function, if such an approximation exists. Its significance for the cryptographic security of SSSCs and its applications in coding theory are discussed.
Overview of Image Security Techniques with applications in multimedia systems
 Proceedings of the SPIE International Conference on Multimedia Networks: Security, Displays, Terminals, and Gateways
, 1997
"... The growth of networked multimedia systems has created a need for the copyright protection of digital images and video. Copyright protection involves the authentication of image content and/or ownership. This can be used to identify illegal copies of a (possibly forged) image. One approach is to mar ..."
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Cited by 21 (5 self)
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The growth of networked multimedia systems has created a need for the copyright protection of digital images and video. Copyright protection involves the authentication of image content and/or ownership. This can be used to identify illegal copies of a (possibly forged) image. One approach is to mark an image by adding an invisible structure known as a digital watermark to the image. Techniques of incorporating such a watermark into digital images include spatialdomain techniques, transformdomain algorithms and subband filtering approaches.
Statistical Techniques for Language Recognition: An Introduction and Guide for Cryptanalysts
 Cryptologia
, 1993
"... We explain how to apply statistical techniques to solve several languagerecognition problems that arise in cryptanalysis and other domains. Language recognition is important in cryptanalysis because, among other applications, an exhaustive key search of any cryptosystem from ciphertext alone requir ..."
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Cited by 11 (2 self)
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We explain how to apply statistical techniques to solve several languagerecognition problems that arise in cryptanalysis and other domains. Language recognition is important in cryptanalysis because, among other applications, an exhaustive key search of any cryptosystem from ciphertext alone requires a test that recognizes valid plaintext. Written for cryptanalysts, this guide should also be helpful to others as an introduction to statistical inference on Markov chains. Modeling language as a finite stationary Markov process, we adapt a statistical model of pattern recognition to language recognition. Within this framework we consider four welldefined languagerecognition problems: 1) recognizing a known language, 2) distinguishing a known language from uniform noise, 3) distinguishing unknown 0thorder noise from unknown 1storder language, and 4) detecting nonuniform unknown language. For the second problem we give a most powerful test based on the NeymanPearson Lemma. For the oth...
An Analysis of the Hart Intercivic DAU eSlate
 In Proceedings of the USENIX/ACCURATE Electronic Voting Technology Workshop (EVT 2007). USENIX Press. [62] Pygame
, 2007
"... This paper reports on an analysis of the Hart InterCivic DAU eSlate unit equipped for disabled access and the associated Judge’s Booth Controller. The analysis examines whether the eSlate and JBC can be subverted to compromise the accuracy of vote totals, the secrecy of the ballot, and the availabi ..."
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Cited by 11 (1 self)
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This paper reports on an analysis of the Hart InterCivic DAU eSlate unit equipped for disabled access and the associated Judge’s Booth Controller. The analysis examines whether the eSlate and JBC can be subverted to compromise the accuracy of vote totals, the secrecy of the ballot, and the availability of the system under the procedures in place for Yolo County. We describe several potential attacks, and show how election officials can block or mitigate them. 1
A New Statistical Testing for Symmetric Ciphers and Hash Functions
 Proc. Information and Communications Security 2002, volume 2513 of LNCS
, 2002
"... This paper presents a new, powerful statistical testing of symmetric ciphers and hash functions which allowed us to detect biases in both of these systems where previously known tests failed. We first give a complete characterization of the Algebraic Normal Form (ANF) of random Boolean functions by ..."
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Cited by 11 (1 self)
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This paper presents a new, powerful statistical testing of symmetric ciphers and hash functions which allowed us to detect biases in both of these systems where previously known tests failed. We first give a complete characterization of the Algebraic Normal Form (ANF) of random Boolean functions by means of the M obius transform. Then we built a new testing based on the comparison between the structure of the different Boolean functions Algebraic Normal Forms characterizing symmetric ciphers and hash functions and those of purely random Boolean functions. Detailed testing results on several cryptosystems are presented. As a main result we show that AES, DES Snow and Lili128 fail all or part of the tests and thus present strong biases.
How to Break Gifford's Cipher
, 1994
"... We present and implement a ciphertextonly algorithm to break Gifford's cipher, a stream cipher designed in 1984 by David Gifford of MIT and used to encrypt New York Times and Associated Press wire reports. Applying linear algebra over finite fields, we exploit a timespace tradeoff to separately de ..."
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Cited by 9 (1 self)
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We present and implement a ciphertextonly algorithm to break Gifford's cipher, a stream cipher designed in 1984 by David Gifford of MIT and used to encrypt New York Times and Associated Press wire reports. Applying linear algebra over finite fields, we exploit a timespace tradeoff to separately determine key segments derived from a decomposition of the feedback function. This work, the first proposed attack on Gifford's cipher, illustrates a powerful attack on stream ciphers and shows that Gifford's cipher is illsuited for encrypting broadcast data in the MITbased Boston Community Information System (BCIS). Gifford's cipher is a filter generatora linear feedback shift register with nonlinear output. Our cryptanalytic problem is to determine the secret 64bit initial fill, which is changed for each news article. Representing the feedback function as a binary matrix F , we decompose the vector space of register states into a direct sum of four F invariant subspaces determined fr...
A Study on the Construction and Analysis of Substitution Boxes for Symmetric Cryptosystems
, 1990
"... S(ubstitution)boxes are quite important components of modern symmetric cryptosystems (in particular, block ciphers) in the sense that Sboxes bring nonlinearity to block ciphers and strengthen their cryptographic security. An Sbox is said to satisfy the strict avalanche criterion (SAC), if and onl ..."
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Cited by 3 (1 self)
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S(ubstitution)boxes are quite important components of modern symmetric cryptosystems (in particular, block ciphers) in the sense that Sboxes bring nonlinearity to block ciphers and strengthen their cryptographic security. An Sbox is said to satisfy the strict avalanche criterion (SAC), if and only if for any single input bit of the Sbox, the inversion of it changes each output bit with probability one half. In this thesis, with the concrete proof of cryptographical properties of Sboxes satisfying the SAC, we propose a variety of provable construction methods for Sboxes satisfying the SAC. For Boolean Sboxes satisfying the SAC, we can construct and enlarge them by using concatenation, Kronecker (or direct) product, and dyadic shift. For bijective Sboxes satisfying the SAC, when an nbit input Boolean function and an nbit input bijective function satisfying the SAC are given, the combined function is proved to become an (n+1)bit bijective function satisfying the SAC as well. A...
Clockcontrolled generators
, 1999
"... A stream cipher generator can not be considered as suitable for stream ciphers applications unless its output sequences have large periods, large linear complexities and possess certain randomness properties. The use of clockcontrolled shift registers in keystream generators appears to be a good wa ..."
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A stream cipher generator can not be considered as suitable for stream ciphers applications unless its output sequences have large periods, large linear complexities and possess certain randomness properties. The use of clockcontrolled shift registers in keystream generators appears to be a good way of achieving sequences with these properties. In this thesis we look at clockcontrolled generators, these are built up from two registers, one controlling the clock of a second register from which the output is taken. Examples that have appeared in the literature include the stop and go generator, the binary rate multiplier, the (a, b) clockcontrolled generator, the cascade generator, and the shrinking generator. The binary rate multiplier and the (a, b) clockcontrolled generator may be seen as generalizations for the stop and go generator. Similarly we introduce generalizations of the cascade generator and the shrinking generator that allows us, by using the same initial states and feedback functions, to produce many more sequences with the same desirable properties as those
Key Schedule Classification of the AES Candidates
, 1999
"... An important component of iterative, block ciphers is the key schedule. In most ciphers, a master key of speci#ed length is manipulated to create round subkeys. This manipulation is known as the key schedule. A strong key schedule means a cipher will be more resistant to various forms of attacks, su ..."
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An important component of iterative, block ciphers is the key schedule. In most ciphers, a master key of speci#ed length is manipulated to create round subkeys. This manipulation is known as the key schedule. A strong key schedule means a cipher will be more resistant to various forms of attacks, such as di#erential and linear cryptanalysis. In this paper, the Advanced Encryption Standard#AES# candidates are classi#ed according to their key schedules. 1 The Classi#cation Schedule The most powerful methods of analysis of iterative block ciphers such as the Data Encryption Standard#DES# #4# are attacks which aim to reveal round subkeys. These methods include di#erential #5# and linear cryptanalysis #9#. In #1#, the authors introduced a new classi#cation scheme for iterative block ciphers based on their key schedules. In essence, this scheme creates two categories of ciphers based on whether or not knowledge of a round subkey generated by the key schedule reveals any information about ot...
An Image Encryption method with Magnitude and Phase Manipulation using carrier images
 IJCS
, 2006
"... Abstract — We describe an effective method for image encryption which employs magnitude and phase manipulation using carrier images. Although it involves traditional methods like magnitude and phase encryptions, the novelty of this work lies in deploying the concept of carrier images for encryption ..."
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Abstract — We describe an effective method for image encryption which employs magnitude and phase manipulation using carrier images. Although it involves traditional methods like magnitude and phase encryptions, the novelty of this work lies in deploying the concept of carrier images for encryption purpose. To this end, a carrier image is randomly chosen from a set of stored images. One dimensional (1D) discrete Fourier transform (DFT) is then carried out on the original image to be encrypted along with the carrier image. Row wise spectral addition and scaling is performed between the magnitude spectra of the original and carrier images by randomly selecting the rows. Similarly, row wise phase addition and scaling is performed between the original and carrier images phase spectra by randomly selecting the rows. The encrypted image obtained by these two operations is further subjected to one more level of magnitude and phase manipulation using another randomly chosen carrier image by 1D DFT along the columns. The resulting encrypted image is found to be fully distorted, resulting in increasing the robustness of the proposed work. Further, applying the reverse process at the receiver, the decrypted image is found to be distortionless.