dixon.tex 871 B

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  1. \chapter{Dixon \label{chap:dixon}}
  2. ~\cite{dixon} describes a class of ``probabilistic algorithms'' for finding a
  3. factor of any composite number, at a computational cost asymptotically best
  4. than all other ones previously described:
  5. \bigO{\beta(\log N \log \log N)^{\rfrac{1}{2}}}
  6. for some constant $\beta > 0$.
  7. \paragraph{Kraitchick} was the first one popularizing the idea the instead of
  8. looking for integers $\angular{x, y}$ such that $x^2 -y^2 = N$ -recall Fermat's
  9. problem, formulated in equation ~\ref{eq:fermat_problem}, it is sufficient to
  10. look for \emph{multiples} of $N$:
  11. \begin{align}
  12. x^2 - y^2 \equiv 0 \pmod{N}
  13. \end{align}
  14. and, once found, claim that $\gcd(N, x \pm y)$ are non-trial divisors of $N$
  15. just as we did in \ref{sec:fermat:implementation}.
  16. On the top of this,
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