Cryptanalysis of "an identity-based society oriented signature scheme with anonymous signers"

In this paper, we show that the identity-based society oriented signature scheme with anonymous signers proposed by saeednia is insecure. If some members of a given group leave that group or if some new members join the group, their secret keys would be revealed. We also propose a simple way to fulfill the task of the identity-based society oriented signature scheme with anonymous signers.