Research On Functional Encryption And Its Applications In Verifiable Outsourcing Computation

Functional Encryption(FE)is a generic public key encryption(PKE)concept,which cov-ers a range of Identity-Based Encryption(IBE),Attribute-Based Encryption(ABE),Inner-Product Encryption and so on advanced PKE primitives.Since its emerging advantages in encrypted data sharing with fine-grained access control abilities and catering for various net-work services' demands,it has received much interest in a wide range of research.Most current works on FE(where IBE and ABE are the typical representatives)aim to give FE schemes with high security guarantee and high efficiency,as well as its applications in network services(e.g.outsourcing computation).However,some FE schemes pursue the improvements on function-ality and efficiency,cannot achieve one or many key points of provable security theory:such as standard model,security based on standard assumptions and constructed using prime-order bilinear groups;not consider some realizations under FE cryptosystem(such as identity-based cryptosystem)for traditional certificate-based PKE notions;verifiable outsourcing computation protocols based on FE approach suffer from constrained delegation computation types and cer-tain flexibility.Therefore,to obtain more secure and more expressive FE with higher efficiency and its flexibility applications in specific network services is one of the recent hot topics.In this thesis,we mainly focus on the design of provably secure functional encryption and its applications in verifiable outsourcing computation field:manages to give two efficient key-policy ABE schemes with constant-size ciphertexts from the starting point of provable se-curity;introduces the identity-based dual receiver encryption(ID-DRE)notion and presents concrete two provably secure ID-DRE constructions;designs two practical verifiable outsourc-ing computation protocols based on the ABE primitive.Specifically,our contributions can be summarized as follows:1.Semi-adaptive Key-Policy Attribute-Based Encryption with Short Ciphertexts.We propose two more efficient semi-adaptively secure key-policy attribute-based encryption(KP-ABE)schemes with constant-size ciphertexts.The semi-adaptive security requires that the adversary submits the challenge attribute set after it receives public parameters but before it issues any secret key query,which is stronger than the selective security guarantee but a little weaker than the adaptive security.Our first construction deals with small universe while the second one supports large universe.Technically,both construc-tions employ the prime-order instantiation of nested dual system groups under d-linear assumption including DLIN and SXDH assumptions.Compared with other KP-ABE schemes with constant-size ciphertexts,our works achieve shorter ciphertext and secret key sizes,and require low computation costs,especially the one from SXDH assumption.Finally,we conduct an experiment using Python language in Charm to illustrate the actual performance on our schemes.2.New Application of Partitioning Methodology:Identity-Based Dual Receiver En-cryption.We study the notion of Dual Receiver Encryption(DRE)in the traditional certificate-based PKE setting,and extend it into the identity-based setting.Hence,we in-troduce the Identity-Based Dual Receiver Encryption(ID-DRE)concept along with giv-ing formal system and security definitions,and present an IND-ID-CPA secure ID-DRE scheme and then improve it to achieve IND-ID-CCA security without using any generic transformation.Technically,after giving a non-trivial combination between ID-DRE's inherent mechanism and Waters' IBE,we revisit the partitioning strategy proof technique by adopting a random walk-like methodology over an analysis on the lower bound of simulators' artificial abort,which also leads to a better security tightness for Waters' IBE.We base the security of both two constructions to the DBDH assumption in the standard model.Moreover,our two ID-DRE schemes enjoy both desirable properties for DRE and high efficiency.3.Practically Efficient and Scalable Public Verifiable Outsourcing Computation Pro-tocol.We study the outsourcing computation for a group of clients(vessels)in marine mobile cloud computing,and list some desirable properties for such an outsourcing com-putation protocol.In order to cater for clients' different delegation computation types in practice,we first propose a "scalable" public verifiable outsourcing computation protocol(towards outsourcing datasets and computations altogether)by modifying Attrapadung and Imai's dual-policy ABE and refining the relation between public verifiable computa-tion and KP-ABE,and finally extract a single mode variant(single outsourced type and single import type)as well.Both two protocols support public verifiable property and public delegation property,which are highly necessary for a group outsourcing computa-tion situation.We additionally prove that both protocols achieve selective soundness in the random oracle model and evaluate their performance in the end.In summary,this thesis focuses on both the design of provably secure functional encryption scheme and its applications in verifiable outsourcing computation.The proposed cryptographic schemes and application protocols not only have certain theoretical significance,but also have further application values in practice.