Research On Conditional Proxy Re-encryption Scheme

Proxy re-encryption can be used to delegate the decryption of a cipher text from one userto another, without losing the confidentiality of the plaintext. Thus, Proxy re-encryptionbecomes increasingly more important in many application fields like Cloud computing ande-mail forwarding etc. In these fields, Proxy re-encryption offers an efficient method ofdelegating decryption. The development of the proxy re-encryption plays an important roleand has become crucial to the technique development in these fields. Therefore, the design ofproxy re-encryption with higher security and efficiency is still a rather challenging task.Especially, fine-grained delegation is often needed in some applications, which isimplemented by conditional proxy re-encryption. So the study of conditional proxyre-encryption is of great theoretical and practical significance.Weng Jian et al. proposed the concept of conditional proxy re-encryption, and gave theformalized definition of conditional proxy re-encryption and the secure model as well. Eversince, various versions of conditional proxy re-encryption schemes were proposed by scholars.However, till now, there is still no CCA secure conditional proxy re-encryption schemewithout parings or CCA secure conditional proxy re-encryption scheme in adaptive corruptedmodel.In this paper, the construction of the proxy re-encryption scheme without pairings isfirstly introduced, and a detailed analysis of the secure properties is made as well. A newproperty for conditional proxy re-encryption, non-dispersibility, is proposed afterwards.Based on these, a CCA secure conditional proxy re-encryption scheme without pairings byusing the technology of token-controlled encryption is put forward.In addition, after the introduction of the conditional proxy re-encryption scheme inadaptive corrupted model without random oracle, a conditional proxy re-encryption inadaptive corrupted model based on the CHK technology is constructed.The last task of this paper is to analyze the application of conditional proxy re encryptionin such fields as cloud computing, encrypted mail forwarding system and so on. Theapplication of it has greatly improved the functions of these systems and enabled the systemusers to assign decryption rights more fine-grained.