Some Words on Cryptanalysis of Stream Ciphers
(2006) Abstract
 In the world of cryptography, stream ciphers are known as primitives used to ensure privacy over a communication channel. One common way to build a stream cipher is to use a keystream generator to produce a pseudorandom sequence of symbols. In such algorithms, the ciphertext is the sum of the keystream and the plaintext, resembling the onetime pad principal. Although the idea behind stream ciphers is simple, serious investigation of these primitives has started only in the late 20th century. Therefore, cryptanalysis and design of stream ciphers are important.
In recent years, many designs of stream ciphers have been proposed in an effort to find a proper candidate to be chosen as a world standard for data encryption.... (More)  In the world of cryptography, stream ciphers are known as primitives used to ensure privacy over a communication channel. One common way to build a stream cipher is to use a keystream generator to produce a pseudorandom sequence of symbols. In such algorithms, the ciphertext is the sum of the keystream and the plaintext, resembling the onetime pad principal. Although the idea behind stream ciphers is simple, serious investigation of these primitives has started only in the late 20th century. Therefore, cryptanalysis and design of stream ciphers are important.
In recent years, many designs of stream ciphers have been proposed in an effort to find a proper candidate to be chosen as a world standard for data encryption. That potential candidate should be proven good by time and by the results of cryptanalysis.
Different methods of analysis, in fact, explain how a stream cipher should be constructed. Thus, techniques for cryptanalysis are also important.
This thesis starts with an overview of cryptography in general, and introduces the reader to modern cryptography. Later, we focus on basic principles of design and analysis of stream ciphers. Since statistical methods are the most important cryptanalysis techniques, they will be described in detail.
The practice of statistical methods reveals several bottlenecks when implementing various analysis algorithms. For example, a common property of a cipher to produce nbit words instead of just bits makes it more natural to perform a multidimensional analysis of such a design. However, in practice, one often has to truncate the words simply because the tools needed for analysis are missing. We propose a set of algorithms and data structures for multidimensional cryptanalysis when distributions over a large probability space have to be constructed.
This thesis also includes results of cryptanalysis for various cryptographic primitives, such as A5/1, Grain, SNOW 2.0, Scream, Dragon, VMPC, RC4, and RC4A. Most of these results were achieved with the help of intensive use of the proposed tools for cryptanalysis. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/25433
 author
 Maximov, Alexander ^{LU}
 opponent

 Ph.D. Daemen, Joan, ST Microelectronics, Belgien
 organization
 publishing date
 2006
 type
 Thesis
 publication status
 published
 subject
 keywords
 VMPC, Dragon, Grain, A5/1, SNOW 2.0, Scream, large distributions, correlation attacks, distinguishing attacks, algorithms, Cryptography, cryptanalysis, RC4, RC4A, Computer science, numerical analysis, systems, control, Datalogi, numerisk analys, system, kontroll
 pages
 256 pages
 publisher
 Department of Information Technology, Lund Univeristy
 defense location
 E:1406, Ehuset, Lunds Tekniska HÃ¶gskola
 defense date
 20060616 10:15
 external identifiers

 Other:LUTEDX/TEIT06/1035SE
 ISBN
 9171670394
 language
 English
 LU publication?
 yes
 id
 b5e4b9b8f9494435a3696df839ca7d23 (old id 25433)
 date added to LUP
 20070608 11:20:12
 date last changed
 20160919 08:45:02
@phdthesis{b5e4b9b8f9494435a3696df839ca7d23, abstract = {In the world of cryptography, stream ciphers are known as primitives used to ensure privacy over a communication channel. One common way to build a stream cipher is to use a keystream generator to produce a pseudorandom sequence of symbols. In such algorithms, the ciphertext is the sum of the keystream and the plaintext, resembling the onetime pad principal. Although the idea behind stream ciphers is simple, serious investigation of these primitives has started only in the late 20th century. Therefore, cryptanalysis and design of stream ciphers are important.<br/><br> <br/><br> In recent years, many designs of stream ciphers have been proposed in an effort to find a proper candidate to be chosen as a world standard for data encryption. That potential candidate should be proven good by time and by the results of cryptanalysis.<br/><br> <br/><br> Different methods of analysis, in fact, explain how a stream cipher should be constructed. Thus, techniques for cryptanalysis are also important.<br/><br> <br/><br> This thesis starts with an overview of cryptography in general, and introduces the reader to modern cryptography. Later, we focus on basic principles of design and analysis of stream ciphers. Since statistical methods are the most important cryptanalysis techniques, they will be described in detail.<br/><br> <br/><br> The practice of statistical methods reveals several bottlenecks when implementing various analysis algorithms. For example, a common property of a cipher to produce nbit words instead of just bits makes it more natural to perform a multidimensional analysis of such a design. However, in practice, one often has to truncate the words simply because the tools needed for analysis are missing. We propose a set of algorithms and data structures for multidimensional cryptanalysis when distributions over a large probability space have to be constructed.<br/><br> <br/><br> This thesis also includes results of cryptanalysis for various cryptographic primitives, such as A5/1, Grain, SNOW 2.0, Scream, Dragon, VMPC, RC4, and RC4A. Most of these results were achieved with the help of intensive use of the proposed tools for cryptanalysis.}, author = {Maximov, Alexander}, isbn = {9171670394}, keyword = {VMPC,Dragon,Grain,A5/1,SNOW 2.0,Scream,large distributions,correlation attacks,distinguishing attacks,algorithms,Cryptography,cryptanalysis,RC4,RC4A,Computer science,numerical analysis,systems,control,Datalogi,numerisk analys,system,kontroll}, language = {eng}, pages = {256}, publisher = {Department of Information Technology, Lund Univeristy}, school = {Lund University}, title = {Some Words on Cryptanalysis of Stream Ciphers}, year = {2006}, }