Research On Identity-Based Public Key Cryptosystem

With the rapid development of information technology and internet technology, the internet plays an important role in people's everyday life. For example, people usually use bank card and e-shopping card and so on. All those must be through the internet for convenient transactions. because of encryption technology or encryption algorithms which have vulnerabilities more or less, some people go through these vulnerabilities and steal Bank customers'account in order to do fictitious trading, the banks and the customers subject to greatly lost. Therefore, information security appears especially important.Shamir proposed identity-based cryptography in 1984. Its aim is to simplify the PKI's management of a variety of certificates. The user's identity and his public key are bound together. The user's public key is the user's identity. The user's phone number, email, and identity card numbers, etc., can be seen as his identity. Identity-based cryptosystem have many advantages: since the user's public key is the user's identity, when encrypting a message, it does not need to know the receiver's any other information and does not need to verify the public key certificate. Users submit their identity to private key generation center, and the private key generation center computes and returns to the users their private keys. Private key generation center does not need to get CA's authority, which is advantage of the identity-based encryption.This paper mainly studies identity-based encryption and improves Gentry's encryption scheme. The improved identity-based encryption cryptosystem, security model, the specific algorithm, security analysis and proof are given. In my new scheme the user's identity is automatically anonymous, and without random oracle model. Finally, compared with the original program in efficiency, because new scheme has four pairings and Gentry's scheme has seven pairings, our new scheme is more efficient than Gentry's scheme.Certificateless public key cryptosystem is considered to be a compromise system of PKI-based public key cryptosystem and public key ID-based cryptosystem. However, this public key cryptosystem is not bonded, and the user generates public key or part of a public key , which makes certificateless public key cryptosystem vulnerable to public key substitution attacks. Liu Jingwei et al proposed an efficient ID-based certificateless signature scheme,Feng Tao et al proposed a partially blind signature scheme without a trusted security PKG. Give the analysis of the two certificateless signature schemes. At last, I think the two schemes are not secure and explain how to attack them.