Cryptanalysis of Harn digital multisignature scheme with distinguished signing authorities [comment]

Presents an insider attack on Harn digital multisignature scheme with distinguished signing authorities. In this attack, any malicious insider attacker without any secret keys of the other signers can forge a valid multisignature for any message. The insider attack cannot be detected by any outsider or verifier. The main complexity of the attack is equivalent to the complexity of computing given. Obviously the above computational task is not difficult to carry out, so the insider attack method is very effective. We would like to also point out that the above insider attack is also successful for other Harn digital multisignature schemes, in which all signers sign the same message.