Provably secure multisignature scheme with document decomposition and signer anonymity

In 1999, Harn proposed a multisignature scheme with distinguished signing authorities (also called a multisignature scheme with document decomposition). In such schemes, a document could be partitioned into subdocuments, and each signer only has the authority to sign one specific subdocument in accordance with his signing responsibility and knowledge domains, instead of the whole one. In this paper, we will propose a new multisignature scheme with document decomposition and signer anonymity, in which any outsider (not a signer) cannot identify the actual signer for a given partial signature or a specific subdocument, while an insider can identify him for the internal audit purpose.