Group signatures are cryptographic privacy-preserving authentication mechanisms. Potential signers are formed into a group, which is managed by a usually centralized authority (group manager). Each group member being in possession of a (valid) membership certificate can sign documents on behalf of the whole group. In addition to various forms of unforgeability the distinguished privacy property of group signatures is that they do not leak any information about the actual signer, except for the validity of the signer's membership in the group. In case of dispute the group manager can, however, identify the signer and possibly prove this fact to a third-party. The concept of group signatures was introduced in 1991 by Chaum and Van Heyst and many more schemes appeared since then. The goal of the project is to reflect the state-of-the-art in this field by providing a comparative study of existing group signatures, thereby focusing on their security and privacy properties, cryptographic strength, performance, and practical relevance.