The invention concerns a method aimed at preventing secret code manipulations in a data processing means, such as a smart card (CA), by applying thereto a presented code. The method for accessing a functionality of the card comprises prior to implementation (E1) of a code transforming function (FT) in the processing means (CP), transformation (E2) of the secret code (CS) into a transformed secret code (CST) in the card. For each use of the card are provided transformation (E6) of the presented code (CP) into a transformed presented code (CPT) in accordance with the implemented transformation function, and a comparison (E7) of the transformed secret code with the transformed secret code in the card.
