Attack on Okamoto et al.'s New Short Signature Schemes.
Fangguo Zhang, Xiaofeng Chen · IACR Cryptology ePrint Archive · 2005
We present an attack on a new short signature scheme from bilinear pairing proposed by Okamoto et al. at ITCC’05. We show that any one can derive the secret key of the signer from any two messagesignature pairs and so can forge the signer’s signature for any message. This means the scheme is totally broken.