Digital watermarking is a promising technology for protecting intellectual property rights on digital content. Resolving authorship-disputes was one of the first and most propelling applications of robust digital watermarks, and much research effort
has gone into protocols for resolving authorship-disputes by means of digital watermarks. Unfortunately, previous proposals lack formal definitions of their trust model, their assumptions, and requirements they should fulfill. This lack of formal definitions makes security proofs for such protocols impossible and many dispute resolving protocols, claimed to be secure, can be shown to be insecure. In this paper we set off to rigorously defining dispute resolving schemes based on a reasonable formal definition of "authorship." Building on this formal fundament, we analyze the most important proposals for dispute resolving, and discuss their connection to our authorship model. We show that existing proposals suffer from two major problems: First, they require an unnecessary high level of trust in the dispute resolving party. The second and even more serious is that the winner of the dispute is not guaranteed to be the rightful author of the disputed work (conclusiveness problem). As solutions, we propose dispute resolving schemes based on zero-knowledge watermark detection and asymmetric watermarking schemes.