Process for manufacturing a sheet of paper and/or board, according to which, in a plant comprising a fan pump and a head box: a cellulose fiber suspension is prepared; the white waters are introduced into the thick stock; the mixture is homogenized in the fan pump; the thin stock is transferred to the head box; the sheet is formed and then dried, characterized in that, before homogenization of the mixture in the fan pump, a cationic copolymer obtained by Hofmann degradation reaction is introduced into the white waters and/or the thick stock and/or the mixture formed by the white waters and the thick stock.