An Attack on a Signature Scheme Proposed by Okamoto and Shiraishi.

Ernest F. Brickell John M. DeLaurentis An Attack on a Signature Scheme Proposed by Okamoto and Shiraishi. 28-32 http://dx.doi.org/10.1007/3-540-39799-X_4 1985 conf/crypto/1985 CRYPTO db/conf/crypto/crypto85.html#BrickellD85