A strong designated verifiable group signature scheme

This paper presents a strong designated verifier group signature scheme, in which signature is generated by any member of the group and it is verified by only a specific receiver, called a designated verifier using the public parameters of the group and his own secret key. The verifier assumes that the signature indeed is from the group itself, not from any individual group member. In this scheme, anonymity of the signer is completely preserved. The verifier cannot link a signature to the signer. The scheme is secure as an adversary cannot verify the signature even if the secret key of the signer is compromised or leaked. Also, neither the group manager nor any member of the group can produce a valid signature on behalf of another member. Only in case of legal disputes, the group manager can disclose the identity of a group member who has signed a document. The major benefit of this scheme is that the length of the group signature is independent of number of group members and it remains unaffected if some members left the group or new members join the group. Security of the proposed scheme lies in the complexity of solving three computationally hard problems, namely, Computational Diffiee-Helmann (CDH) problem, Discrete Logarithm Problem (DLP) and Integer Factorization Problem (IFP). This scheme can be useful in organizations where there is a need to send confidential documents to a specific recipient. This scheme can also be applicable to real life scenarios, such as, e-commerce applications, e-banking and e-voting.