A CCA Secure Identity-based Threshold Encryption

Public key cryptography is a great and revolutionary achievement in the history of cryptography.In 1976,the idea of public key cryptography was first introduced publicly,and then a large number of public key cryptography schemes were proposed.However,the problem of public key authentication is existed generally in the public key cryptosystem,which is solved by certificates in the public key infrastructure.But the management of certificates is very tedious,which inspires people to propose identity-based encryption.However,in the identity-based encryption system,the power of the trusted center is too great,and the trusted center knows the private key of each user.In order to decentralize the rights of trusted centers,scholars proposed identity-based threshold public key encryption.In this paper,the identity-based threshold public key encryption is studied,and a non-interactive identity-based threshold public key encryption scheme is proposed,which can be proved to be CCA secure in the random oracle model.In fact,the work of this article is carried out in two steps.First,we use a simple conversion to get a general method which improves the security of an identity-based encryption from CPA to CCA,then using the method,we construct a CCA secure identity-based threshold encryption scheme.In the existing literature,there are few CCA secure threshold schemes,and some efficient CCA secure public key encryption schemes use private keys for ciphertext validation,so it is difficult to be extended to the threshold scheme(for example,cramer-shoup scheme).In addition,in some existing threshold schemes of CCA security,the transformation from CPA to CCA requires an additional signature or a message authentication code for each encryption,which leads to low efficiency and increases the length of ciphertext.However,in this paper,the ciphertext validity of the encryption scheme can be verified publicly,so the scheme can be extended to a threshold scheme naturally,and the scheme has short public key,short ciphertext and tight security reduction.