145 research outputs found
Trivalent Graph isomorphism in polynomial time
It's important to design polynomial time algorithms to test if two graphs are
isomorphic at least for some special classes of graphs.
An approach to this was presented by Eugene M. Luks(1981) in the work
\textit{Isomorphism of Graphs of Bounded Valence Can Be Tested in Polynomial
Time}. Unfortunately, it was a theoretical algorithm and was very difficult to
put into practice. On the other hand, there is no known implementation of the
algorithm, although Galil, Hoffman and Luks(1983) shows an improvement of this
algorithm running in .
The two main goals of this master thesis are to explain more carefully the
algorithm of Luks(1981), including a detailed study of the complexity and, then
to provide an efficient implementation in SAGE system. It is divided into four
chapters plus an appendix.Comment: 48 pages. It is a Master Thesi
Quantum Fourier sampling, Code Equivalence, and the quantum security of the McEliece and Sidelnikov cryptosystems
The Code Equivalence problem is that of determining whether two given linear
codes are equivalent to each other up to a permutation of the coordinates. This
problem has a direct reduction to a nonabelian hidden subgroup problem (HSP),
suggesting a possible quantum algorithm analogous to Shor's algorithms for
factoring or discrete log. However, we recently showed that in many cases of
interest---including Goppa codes---solving this case of the HSP requires rich,
entangled measurements. Thus, solving these cases of Code Equivalence via
Fourier sampling appears to be out of reach of current families of quantum
algorithms.
Code equivalence is directly related to the security of McEliece-type
cryptosystems in the case where the private code is known to the adversary.
However, for many codes the support splitting algorithm of Sendrier provides a
classical attack in this case. We revisit the claims of our previous article in
the light of these classical attacks, and discuss the particular case of the
Sidelnikov cryptosystem, which is based on Reed-Muller codes
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