Research On Several Types Of Cryptography Schemes Under The Certificate Based Public Key Cryptosystem

In the process of the development of social informatization,the increasing problem of network information security has attracted wide attention.Cryptography is an important theoretical and technical basis for the realization of network information security.It can realize the security characteristies of confidentiality,integrity,authentication and non-repudiation of information.Certificate public key cryptosystem can not only solve the problem of certificate management in traditional public key cryptosystem,but also overcome the problem of key escrow in identity public key cryptosystem.At the same time,it can avoid the problem of secure distribution of some private keys and lack of public key authentication in certificateless public key cryptosystem.Therefore,it is very important to study and design the cryptographic scheme under certificate public key cryptosystem.Denial of authentication encryption technology can not only ensure the confidentiality of data and user authentication,but also protect user's identity privacy.Keyword searchable encryption technology can realize encrypted data outsourcing and storage in cloud server.At the same time,it can also let cloud server to perform encrypted data retrieval operation according to keyword trap-door submitted by users.Aggregated signature can aggregate the signatures of multiple users to generate a signature.Verifiers can verify the aggregated signature to achieve batch verification of multiple user signatures.In order to protect users' data and identity privacy and enhance the security of the scheme,this paper studies and designs denial authentication encryption scheme,keyword searchable encryption scheme and aggregate signature scheme based on certificate public key cryptosystem.The main work of this paper includes the following three aspects:(1)We proposed a certificate denial authentication encryption scheme with privacy protection.In order to avoid.exposing the identity privacy of voters in electronic voting applications,a certificate denial authentication encryption scheme is proposed.Under the random oracle model,it is proved that the scheme satisfies the unforgeability and denial under adaptive selection message attack.User's identity privacy can be protected by denial.(2)We proposed a certificate encryption scheme supporting keyword search.In order to meet the needs of cloud storage and retrieval of cloud-based encrypted data,combining the advantages of certificate public key cryptography and searchable encryption,a certificate public key searchable encryption scheme is proposed.Under the random oracle model,it is proved that the scheme has the indistinguishability of ciphertext under the attack of adaptive choice of keywords.(3)We analyzed and improved a certificate aggregation short signature scheme.Firstly,the security of Li certificate aggregation short signature scheme is analyzed,and it is pointed out that the scheme is not secure.Then two kinds of specific attacks are constructed and the reasons for the attacks are analyzed.Finally,an improved certificate aggregation short signature scheme is proposed.Under the random oracle model,it is proved that the scheme is unforgettable under adaptive selection message attack.On the premise of retaining the advantages of the original scheme,the improved scheme improves the security of the scheme.