In order to promote its "xxx" signal encoding algorithm, company X offers users of a particular encoder (21) the possibility to up-load (parts of) their .xxx files to the company's website. The company's web-server (1) checks whether the received file is indeed xxx-encoded material by (i) decoding the file using an xxx-decoder (11), (ii) deriving a fingerprint (12) from the decoded signal, and (iii) awarding the owner if the derived fingerprint corresponds to one of the fingerprints stored in X's database (14). A possible award is the transmission, to the user, of metadata associated with the signal such as title, artist, lyrics, etc.