Abstract: A method of making secure the use of a piece of software, the method consisting: in a substage of generating modified data (D?): for a first category of users possessing a generation unit (11g) including at least one generation secret (Sg) to be able to obtain modified data (D?); and for a second category of users not possessing the generation unit (11g), to be able at best to generate original data (D) without being able to translate it in order to obtain modified data (D?); and in a substage of reconstituting original data (D): for a first category of users possessing a reconstitution unit including at least a reconstitution secret, to be able to restore the original data (D); and for a second category of users not possessing the reconstitution unit, to be able at best to use the modified data (D?).

Abstract: The invention provides a method of making a user piece of software secure by means of a user processing and memorizing unit (11u) containing at least one user secret (Su). According to the invention, the method consists in: making a user piece of software and modified data (D?) available to a user; and in a stage of running the user piece of software with the associated modified data (D?), enabling the user possessing the user unit (11u) to recover the original data (D) from the modified data (D?).

Abstract: The subject of the invention concerns a process and a system to limit the possibility to transform data, the transformation of TX-type data into TY-type data being carried out using an A-type transformation function, while the transformation of TY-type data into TX-type data is carried out using a B-type transformation function, inverse of the A-type transformation function, the data being in particular designed to constitute for instance pre-payment tokens. According to the invention, the system includes at least one A-type data processing system (STDA), at least one B-type data processing system (STDB), at least one link, at least once, between the system (STDA) and the system (STDB), at least one A-type processing and memorizing unit (UTMA) including at least the A-type transformation function, at least one B-type processing and memorizing unit (UTMB) including the B-type transformation function and not including the A-type transformation function.