SECURITY PAPER

The invention mainly concerns a fibrous substrate obtained by a wet process, resistant to crumpling and to dirt, in particular of the banknote type, characterised in that it comprises, by weight, at least: - 40% to 96% by dry weight of fibres, in particular cellulose fibres, relative to the dry weight of the substrate, - 1% to 20% by dry weight relative to the dry weight of fibres, of at least one anionic polymer having a glass transition temperature higher than -40°C, and being present in a precipitated form on the surface of the fibres, - 0.5% to 5% by dry weight of at least one cationic precipitation agent, relative to the dry weight of fibres, and - 0.001% to 1% by dry weight of at least one biocidal agent. It also concerns the method for preparing same.