Research On Provably Secure Certificateless Signature Schemes

To solve the key escrow problem of identity-based cryptography,certificateless public key cryptography was proposed.The same as identity-based cryptography,certificateless public key cryptography does not require certificate guarantee the authenticity of public keys,and simplify the complex certificate management system.This advantage is what makes it attractive to researchers.However,the lack of certificate lead to the system is vulnerable to public keys replacement attack and dishonest KGC attack.Thus,studying provably secure efficient certifateless signature schemes has been an active research hot topic.This dissertapon aims to study efficient provably secure certifateless signature schemes.The major contributions of the dissertation are as follows.Through studying the existing signature schemes,a class of provably secure certificateless signature schemes based on elliptic curve discrete logarithm problem is proposed.The formal security proof of proposed shemes is given.The proposed shemes can resist two types of super adversary.Furthermore,the proposed scheme is more computationally efficient than the existing schemes.We analyze the security of Fan et al's certificateless signature scheme and propose improved schemes.Fan et al's recently proposed an efficient certificateless signature scheme and claimed that their scheme is existentially unforgeable in adaptive chosen-message attacks.Through carrying out cryptanalysis,we found their scheme can not resist forgery attack of strong type I adversary.To overcome this security weakness,we propose improved schemes with higher security.The improved schemes solve the security problem that exists in Fan et al's scheme.The improved schemes are existentially unforgeable in adaptive chosen-message attacks in random oracle model.Proxy signature is widely used in electronic commerce,distributed system,grid computing and so on.The existing certificateless proxy signature schemes mostly use bilinear paring.But the implementations of bilinear pairings are extremely time-consuming.The computational efficiency of these schemes using bilinear pairing is inefficient.To improve the computational efficiency,we propose an efficient provably secure certificateless signature scheme without bilinear pairing based on elliptic curve discrete logarithm problem,and prove its security in random oracle model.The proposed scheme can resist two types of super attackers.The proposed scheme is suitable for the situations with limited bandwidth and power-constrained devices.