Research On Key Issues Of Timed-Release Encryption And Its Application

Many practical applications of information security are time-sensitive such as sealed-bid auctions, electronic voting, conditional e-cash, electronic confidential archives, on-line examinations, key management, mortgage payments electronic multi-media magazines and electronic multi-media magazines. In these applications, the kernel information must be seen sensitive before a specific time and thus protected in a way of encryption. Meanwhile, it must be allowed to be decrypted duly by the target receiver after this specific time. Timed-release encryption (TRE) is a cryptographic primitive in which the sender encrypts a message in a way that allows to protect the message from being decrypted by the receiver or anyone else until a future pre-set release time specified by the sender. TRE can meet the demand of the specified security applications mentioned above.This dissertation mainly launches the research in two aspects:improving the TRE theory itself and extending the application fields of TRE. The main results of this research are presented as follows:(1) The comprehensive research of TRE. By summarizing existing TRE schemes and analyzing their characteristics, this dissertation gives the formal definition and security goals definition of TRE. Then, this dissertation comprehensively analyzes the security goals of TRE (specifically the message confidentiality and message unforgeability), as well as their security bounds under the adaptive chosen-plaintext attack and adaptive chosen-ciphertext attack models. Finally, this dissertation conducts research on the application of TRE; especially proposes the preconditions and generic schemes for combining TRE with other cryptographic mechanisms.(2) The research of timed-release encryption using identity-based and proxy re-encryption (IBPR-TRE). The goal of this work is to solve the TRE problem efficiently and securely in the scenarios of large-scale user and ciphertext. Firstly, this dissertation formalizes the notion of IBPR-TRE and its security game model. Secondly, this dissertation proposes two provably secure constructions of IBPR-TRE which are both secure under the q truncated decisional augmented bilinear Diffie-Hellman exponent (q-ABDHEt) assumption in the standard model. The first scheme is secure under the adaptive chosen-plaintext attack while the second scheme is secure under adaptive chosen-ciphertext attack. The proposed schemes use the technology of identity-based encryption and proxy re-encryption, which have the following characteristics:(a) it can resist the collusion between the agent and any receiver;(b) it can easily revoke any user’s authority;(c) it achieves constant costs from the sender’s and the recipient’s point of view. This dissertation also gives the rigorous proof of the assertion that the first scheme is secure against adaptive chosen plaintext attack assuming q-ABDHEt is intractable. Finally, the efficiency analysis shows that, comparing with the existing CCA schemes, the new proposed CCA scheme achieves higher efficiency and better performance.(3) The research of public key timed-release searchable encryption (PKTRSE) in one-to-one scenarios. The goal of this work is to solve the time-sensitive ciphertext retrieval problem. Firstly, this dissertation formalizes the notion of PKTRSE and its security game model. Secondly, this dissertation proposes two provably secure constructions of PKTRSE. The first one is secure under the bilinear Diffie-Hellman (BDH) assumption in the random oracle model while the second one is secure under the q decisional bilinear Diffie-Hellman inversion (q-DBDHI) assumption without random oracles. Then, this dissertation gives the rigorous proof of the assertion that the first scheme is semantically secure against a chosen plaintext attack in the random oracle model which assumes BDH is intractable. The computational efficiency shows that the second one is more efficient than the first scheme obviously.(4) The research of public key timed-release searchable encryption in one-to-many scenarios. The goal of this work is to solve the time-sensitive ciphertext retrieval problem in cryptographic cloud storage scenarios. Firstly, this dissertation formalizes the notion of one-to-many PKTRSE (PKTRSEOM) and its security game model. Secondly, this dissertation proposes two provably secure constructions of PKTRSEom which are secure under the q-DBDHI assumption. The former focuses on security while the latter pays more attention to practicality. Then, this dissertation gives the rigorous proof for both schemes. The efficiency analysis shows that the two schemes achieve constant costs from the sender’s and the recipient’s points of view in the running process of the system.In conclusion, the problems of TRE with multi user and timed-release searchable encryption in cloud computing scenarios are solved effectively, which improves TRE significantly and makes it possible for TRE to solve more cryptographic problems with time properties.