Another credential form that adds a new feature to anonymous credentials: multi-show unlinkability. These are the group signature related credentials of Camenisch et al. The introduction of Group signatures opened up the possibility of multi-show unlinkable showing protocols. While blind signatures are highly relevant for electronic cash and one-show credentials, a new cryptographic primitive, called group signature, opened new possibilities for the construction of privacy enhancing protocols. As is observed in their article, group signatures bear a resemblance to Chaum's concept of credential systems.