The advent of the Web, electronic commerce and the creation of electronic distribution channels for content have brought new challenges regarding the protection of intellectual property. As it has become increasingly difficult to protect the distribution medium against copying, techniques for asserting the copyright on information have gained in importance. A particularly promising method is the use of digital watermarking to embed additional copyright information within data. However, central servers or certification authorities are required by most current watermarking protocols, thus limiting the wide-spread application of watermarking in electronic commerce applications.