Integrity of Anonymous Data

This chapter discusses schemes to confirm that data owned by anonymous entities are legitimate ones, in other words, to protect data owned by anonymous entities from their illegitimate modifications, forgeries, additions, and deletions. Blind Signature schemes enable entity P to obtain the signature of other entity on its data M without disclosing M, therefore later on P can prove the authenticity of M without disclosing its identity. Unlinkable signatures on data ensure that signers had honestly signed on only and all eligible data while disabling anyone including data owners and signers to know correspondences between the data and their signed forms, and implicit transaction links (ITLs) can be used to force entities not to delete their maintaining data without knowing the data themselves. These schemes enable developments of homomorphic anonymous tokens and anonymous credentials, where entities can prove their eligibilities while maintaining their anonymities by showing tokens or credentials. They also enable the identifications of dishonest entities, while preserving privacies of honest entities.