Study On Identity Based Anonymous Broadcast Encryption Scheme

Broadcast encryption is a kind of point-to-multipoint public key encryption,which has higher communication efficiency and wider application compared with traditional point-to-point encryption.In a broadcast encryption scheme,broadcaster sends encrypted message(i.e.ciphertext)to multiple users via an unsafe broadcast channel simultaneously,in which only authorized users can decrypt and access the original message(i.e.plaintext).But unauthorized users can not obtain any valuable information from the ciphertext.Anonymity of broadcast encryption means that no one knows whom the encrypted message is sent to.Thus the recipient user's privacy is protected.At present,there are still some problems need to be further studied and solved in security and efficiency of anonymous broadcast encryption.Therefore,how to design a secure,efficient and anonymous broadcast encryption system in the standard model has become one of the hot issues in the field of cryptography.This thesis focuses on the study of design and security proof of identity based anonymous broadcast encryption scheme in the standard model.The main contributions can be summarized as follows:(1)Under the composite order,based on the symmetric bilinear pairings,identity based anonymous broadcast encryption scheme in standard model is proposed.Firstly,the formal definition and security model of identity based anonymous broadcast encryption are given.Then a specific build of the scheme is proposed.Finally,using the dual system encryption technique,the proposed scheme is proved to meet IND-CPA(Indistinguishability Adaptive Chosen Plaintext Attack)based on the three static assumptions.The analysis shows that the length of private key requires only two group elements and the computational efficiency is improved.Moreover,it can satisfy the anonymity.(2)Under the prime order,based on the asymmetric bilinear pairings,identity based anonymous broadcast encryption scheme in standard model is proposed.This construction utilizes the dual pairing vector space technique.Firstly,the formal definition and security model of identity based anonymous broadcast encryption are given.Then a specific build of the scheme is proposed.Finally,using the dual system encryption technique,the proposed scheme is proved to be fully security under the symmetric External Diffie-Hellman(SXDH)assumption.The analysis shows that proposed scheme achieves constant-size system parameters,private keys and ciphertexts under the prime order.In addition,the proposed scheme satisfies the user's identity anonymity.