The paper proposes a secure and efficient group blind signature based on a group signature which is not coalition-resistant by adding random number to the secret key and introducing blind signature of knowledge.

They considerd their scheme possible to satisfy multed security requirements to resisit coalition attacks.

And the scheme does not satisfy the properties of against coalition attack.

A coalition attack that the manager and the revocation center could conspire to generate valid group signatures and impose them on an arbitrary member of the group was presented.

This new scheme not only solves the problem that QCX scheme has not the property of strong identifiablity through introducing the set ASI in the threshold proxy signature but also overcomes the security leaks such as collusion attack,the original forgeable attack in the congener schemes.

Comparing with other scholar\'s off-line TTP multi-party non-repudiation protocols, our protocol meets consistent evidence properties, which means that whenever protocol finished through TTP, the evidence participants got is consistent, in the meanwhile, our protocol can provide non-repudiation, strong fairness, confidentiality and collusion attack freeness.