Title
Decrypting a Class of Stream Ciphers Using Ciphertext Only
Abstract
Pseudonoise sequences generated by linear feedback shift registers [1] with some nonlinear combining function have been proposed [2]-[5] for cryptographic applications as running key generators in stream ciphers. In this correspondence it will be shown that the number of trials to break these ciphers can be significantly reduced by using correlation methods. By comparison of computer simulations and theoretical results based on a statistical model, the validity of this analysis is demonstrated. Rubin [6] has shown that it is computationally feasible to solve a cipher proposed by Pless [2] in a known plaintext attack, using as few as 15 characters. Here, the number of ciphertext symbols is determined to perform a ciphertext-only attack on the Pless cipher using the correlation attack. Our conclusion from the analysis is that the pseudonoise generator's output sequence and the sequences generated by the linear feedback shift registers should be uncorrelated. This leads to constraints for the nonlinear combining function to be used.
Year
DOI
Venue
1985
10.1109/TC.1985.1676518
IEEE Trans. Computers
Keywords
Field
DocType
ciphertext-only attack,stream cipher,correlation method,ciphertext symbol,cryptographic application,correlation attack,plaintext attack,linear feedback shift register,key generator,computer simulation,cryptanalysis,correlation
Cipher,Computer science,Known-plaintext attack,Algorithm,Cryptanalysis,Arithmetic,Stream cipher,Ciphertext,Linear cryptanalysis,Correlation attack,Differential cryptanalysis
Journal
Volume
Issue
ISSN
34
1
0018-9340
Citations 
PageRank 
References 
241
62.51
2
Authors
1
Search Limit
100241
Name
Order
Citations
PageRank
T. Siegenthaler124565.05