\chapter{Dixon \label{chap:dixon}}

~\cite{dixon} describes a class of ``probabilistic algorithms'' for finding a
factor of any composite number, at a computational cost asymptotically  best
than all other ones previously described:
\bigO{\beta(\log N \log \log N)^{\rfrac{1}{2}}}
for some constant $\beta > 0$.

\paragraph{Kraitchick} was the first one popularizing the idea the instead of
looking for integers $\angular{x, y}$ such that $x^2 -y^2 = N$ -recall Fermat's
problem, formulated in equation ~\ref{eq:fermat_problem}, it is sufficient to
look for \emph{multiples} of $N$:
\begin{align}
  x^2 - y^2 \equiv 0 \pmod{N}
\end{align}
and, once found, claim that $\gcd(N, x \pm y)$ are non-trial divisors of $N$
just as we did in \ref{sec:fermat:implementation}.
On the top of this,

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