Abstract: The product/program and the process according to the invention make it possible to insert into an item of software in source code, in particular Java, watermarks which comply with the semantics of the program and are very difficult to detect. They make it possible to: compute a secret semantic signature of a software or hardware computer program from an infinity of possible secret semantic signatures; —mark a software or hardware computer program by inserting a visible or invisible watermark making it possible to retrieve an authenticator of the original program; retrieve the mark and extract this authenticator from the secret semantic signature of the watermarked software or hardware computer program. The secret semantic signature of the software or hardware computer program to be protected is characteristic of the semantics of said program.