Cryptanalysis of Provably Secure Certi cateless Short Signature Scheme.
Jayaprakash Kar · 2015
Abstract. Recently, Choi et al. proposed certificateless short signature scheme in random oracle model and the author claims that it is provably secure. Certificateless Public Key Cryptography is a new paradigm, where it allows resolving the inherent key escrow and key management problem. Attack to certificateless signature scheme are of two types as Type-I where the adversary can replace the public key of the user and cannot able to retrieve the master secret key from Key Generator Center (KGC). In Type-II, the adversary can able to obtain the master secret key and cannot replace the public key of the user. In this paper we have proven that, the proposed scheme is not secure against Type-I adversary. To prove, we solve linear Diophantine equation and obtain the partial-private key of the user. Keywords:Diophantine equation, Bilinear map, Digital signature, Certificateless sig-nature