ABSTRACT
A digital copyright is a signature added to a digital multimedia contents. The copyright has been used to establish authorship and to check if the data has been tampered with. In existing copyright protection schemes based on ordinary signature scheme, some one can make counterfeited copyright and embeds it to the copyrighted digital contents to assert multiple claims of rightful authorship. In this case, an original author wants to make the copyright which can not be verified without help of the author so that only the intended verifier can be convinced about the validity of it.
In undeniable signature scheme, the signature can be verified and disavowed only with cooperation of the signer. If the copyright has property of undeniable signature, the verifier can not distinguish between valid and invalid copyright without help of the copyright owner. Generally, the digital multimedia contents is made by many authors. In application that requires many authors and a designated verifier, an algorithm for undeniable multi-signature is needed.
In this paper, the digital copyright protection scheme based on undeniable multi-signature scheme is proposed. The copyright can be verified and disavowed only in cooperation with all signers. Our scheme is secure against active attacks such as signature modification and repudiation of signature by signers. It can be applied to fair on-line sales of coauthoring copyrighted digital multimedia contents.
