  With privacy-preserving and traceability properties, group signature is a
cryptosystem with central role in cryptography. And there are lots of
application scenarios. A new extension concept of group signature is presented,
namely group signature with self-proof capacity. For a legitimate group
signature, the real signer can prove that the signature is indeed signed by
him/her. While for the other members of the group, they can prove that the
signature is not signed by him/her. The former can be used for claiming money
reward from the police, while the latter can be used for proving one's innocent
in a criminal investigation.
