METHOD OF PROTECTING DIGITAL DOCUMENTS AGAINST UNAUTHORIZED USES

The method comprises: taking a digital document for protection that constitutes a piece of source code, and identifying therein a programming language L defined by a grammar GL; associating an action grammar module with said programming language L; performing a structural characterization of the code in a single syntactic analysis pass on the basis of the action grammar module; this being done by constructing a grammar dictionary GDL associated with the programming language and comprising a set of structural terms such that each of these terms is associated with a rule or a set of rules belonging to said grammar (GL) and by transforming the source code into a structural sequence (RL, TL, GDL) comprising the set of structural terms and the dictionary GDL of the grammar of the language L; proceeding in the same manner to transform a digital document for analysis into a structural sequence (RL, TL, GDL); and measuring the plagiarism ratio between the source code of the digital document for protection and the source code of the digital document for analysis with the help of quantification of the alignment ratio between the respective structural sequences of the source code of the digital document for protection and the digital document for analysis.