By Topic

Cryptanalysis of three mutually clock-controlled stop/go shift registers

Sign In

Cookies must be enabled to login.After enabling cookies , please use refresh or reload or ctrl+f5 on the browser for the login options.

Formats Non-Member Member
$33 $13
Learn how you can qualify for the best price for this item!
Become an IEEE Member or Subscribe to
IEEE Xplore for exclusive pricing!
close button

puzzle piece

IEEE membership options for an individual and IEEE Xplore subscriptions for an organization offer the most affordable access to essential journal articles, conference papers, standards, eBooks, and eLearning courses.

Learn more about:

IEEE membership

IEEE Xplore subscriptions

1 Author(s)
J. D. Golic ; Sch. of Electr. Eng., Belgrade Univ., Serbia

A binary stream cipher consisting of three short linear-feedback shift registers (LFSRs) of total length 64 that are mutually clocked in the stop/go manner is cryptanalyzed in the known keystream sequence scenario. To reconstruct the internal state candidates at a known time from about 64 known keystream bits, two algorithms are developed. One is based on guessing a number of elements of the clock-control sequence and has a computational complexity of about 240 steps, where the average step complexity is comparable to the step complexity of the exhaustive search method. The other exploits a time-memory tradeoff based on the well-known birthday paradox and is successful if approximately T·M⩾264, where T is the required computational time in table lookups and M is the memory in 64-bit words. As the state-transition function is not one-to-one, to recover the initial state from the internal state candidates, two algorithms are introduced. One consists in guessing the number of clocks for each of the LFSRs. The other consists in the reversion of the internal states and is based on the theory of critical and subcritical branching processes

Published in:

IEEE Transactions on Information Theory  (Volume:46 ,  Issue: 3 )