26,446 research outputs found
Modified Alternating Step Generators
Irregular clocking of feedback shift registers is a popular technique to improve parameters of keystream generators in stream ciphers. Another technique is to implement nonlinear functions. We join these techniques and propose Modified Alternating Step Generators built with linear and nonlinear feedback shift registers. Adequate nonlinear Boolean functions are used as feedbacks or as filtering functions of shift registers in order to increase complexity of sequences produced by individual registers and the whole generator. We investigate basic parameters of proposed keystream generators, such as period, linear complexity and randomness
A Simple Attack on Some Clock-Controlled Generators
We present a new approach to edit distance attacks on certain
clock-controlled generators, which applies basic concepts of Graph Theory to
simplify the search trees of the original attacks in such a way that only the
most promising branches are analyzed. In particular, the proposed improvement
is based on cut sets defined on some graphs so that certain shortest paths
provide the edit distances. The strongest aspects of the proposal are that the
obtained results from the attack are absolutely deterministic, and that many
inconsistent initial states of the target registers are recognized beforehand
and avoided during search
Concordance homomorphisms from knot Floer homology
We modify the construction of knot Floer homology to produce a one-parameter
family of homologies for knots in the three-sphere. These invariants can be
used to give homomorphisms from the smooth concordance group to the integers,
giving bounds on the four-ball genus and the concordance genus of knots. We
give some applications of these homomorphisms.Comment: Minor revision, corrected typos and added explanation to Chapter
Post Quantum Cryptography from Mutant Prime Knots
By resorting to basic features of topological knot theory we propose a
(classical) cryptographic protocol based on the `difficulty' of decomposing
complex knots generated as connected sums of prime knots and their mutants. The
scheme combines an asymmetric public key protocol with symmetric private ones
and is intrinsecally secure against quantum eavesdropper attacks.Comment: 14 pages, 5 figure
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