Research On Leakage-resilient Attribute-based Encryption Schemes

Traditionally,the security of cryptographic systems is analyzed in an idealized setting where secret keys and other internal state are not leaked to the adversary.However,this idealized assumption does not hold in real life.It has been shown that various side-channel attacks,exploiting the physical nature of cryptographic operations,such as radiation,temperature,timing or power,can be used to obtain information about secret keys.That is,key leakage has become one of the greatest barriers to the security of cryptosystem.The improvement of the nature on the physical computer to eliminate side-channel attacks has considerable difficulty.Responding to this challenge,leakage-resilient cryptography was introduced to provide such security guarantees.Leakage-resilient cryptography defines a class of computable leakage function applied to secret keys and other internal state to simulate a large class of leakage.It is designed to remain provably secure even if some information about the private key is leaked.The common goal of leakage-resilient cryptography is to design cryptographic systems resilient to large amounts of leakage.So in practice,the cryptosystem makes reliable safety.The thesis focus on leakage-resilient attribute-based encryption and puts emphasis on constant size ciphertexts,anonymity and hash proof system.The main results are specified as follows:1)An efficient attribute-based encryption scheme resilient to continual auxiliary leakage with constant size ciphertexts is proposed.It achieves leakage-resilience and simultaneously has shorter public keys and ciphertexts.To this end,Goldreich–Levin theorem is adopted.Furthermore,the proposed scheme can be realized as resilience against continual leakage if keys are periodically updated.Under three static assumptions,the introduced scheme uses dual system encryption to achieve adaptive security in the standard model.2)Novel leakage-resilient attribute-based encryption schemes from hash proof system are constructed.The leakage rate in almost all of the existing ABE schemes is restricted with a leakage parameter.It implicitly suggests that higher leakage rate results in larger ciphertexts and keys.To overcome this drawback,the notion of hash proof system is generalized to attribute-based setting.And novel leakage-resilient ABE schemes are proposed by applying attribute-based hash proof system.In addition,the results in theoretical analyses and simulation experiments indicate that the proposed scheme is efficient and practical.3)An anonymous ABE scheme in the bounded leakage model is constructed.In most existing attribute-based encryption schemes,the encryptor sends ciphertexts and access policy to users.However,many attributes are sensitive and related to the identity of eligible users.Aiming at tackling the challenge above,the proposed scheme hides the access policy in ciphertexts.It uses LSSS as access structures and achieves adaptive security in the standard model.