  This document summarizes the experience of Julien Voisin during the 2011
edition of the well-known \emph{Google Summer of Code}. This project is a first
step in the domain of metadata anonymization in Free Software. This article is
articulated in three parts. First, a state of the art and a categorization of
usual metadata, then the privacy policy is exposed/discussed in order to find
the right balance between information lost and privacy enhancement. Finally,
the specification of the Metadata Anonymization Toolkit (MAT) is presented, and
future possible works are sketched.
