Bei Liang

Attribute-Based Signatures for Circuits from Multilinear Maps

In this paper, we construct an Attribute-Based Signature (ABS) scheme for general circuits from multilinear maps. Our scheme is inspired by Garg et al.’s Attribute-Based Encryption (ABE) scheme at CRYPTO 2013. We prove selective unforgeability of our scheme in the standard model under the Multilinear Computational Diffie-Hellman (MCDH) assumption. The privacy security of our scheme is perfect.

Leakage-Resilient Zero-Knowledge Proofs of Knowledge for NP

Leakage-resilient zero-knowledge proofs for all NP was presented by Garg et al in 2011. How to construct leakage-resilient zero-knowledge proofs of knowledge for all NP languages is an interesting problem. This paper focuses on this problem and presents a constructions of leakage-resilient zero-knowledge proofs of knowledge for HC (Hamiltonian Cycle) problem.

One-Round Witness Indistinguishability from Indistinguishability Obfuscation

In this work, we build up the relationship between witness indistinguishability (WI) and indistinguishability obfuscation (\(i\mathcal{O}\)) by constructing a one-round witness indistinguishable argument system for all languages in NP based on the existence of indistinguishability obfuscator for general circuit class and a number-theoretic assumption. The key tool in our construction is witness encryption scheme with unique decryption which is also proposed and constructed in this work. Our construction of witness encryption scheme with unique decryption is based on a general witness encryption scheme and a weak auxiliary input multi-bit output point obfuscation.

Leakage-Resilient Proxy Signatures

We design a proxy signature in the setting of leakage-resilient cryptography for the first time. Our motivation is that the proxy signatures are often used in scenarios where the signing is done in an insecure environment, e.g., the proxy key is stored in a device which is not secure enough example of IC card. In such setting, an adversary who can launch side-channel attacks may detect some leakage information about the proxy key. The traditional security models of the proxy signatures cannot provide such security. Hence we extend them to the leakage-resilient setting, and also give a concrete construction which conforms to the extended security model.

Verifiable Random Functions from (Leveled) Multilinear Maps

Verifiable random functions (VRFs), firstly proposed by Micali, Rabin, and Vadhan (FOCS 99), are pseudorandom functions with the additional property that the party holding the seed sk can generate a non-interactive, publicly verifiable proof \(\pi \) for the statements “\(F_{sk}(x)=y\)”, for any input x. To date only a few VRF schemes are known and most known constructions either allow only a small input space, or don’t achieve full adaptive security under a non-interactive complexity assumption. The only known adaptively secure VRF scheme with exponentially-large input space is based on \(\ell \)-Decisional Diffie-Hellman Exponent assumption (Hohenberger and Waters, Eurocrypt 2010).

Secure Mobile Agent from Leakage-Resilient Proxy Signatures

A mobile agent can sign a message in a remote server on behalf of a customer without exposing its secret key; it can be used not only to search for special products or services, but also to make a contract with a remote server. Hence a mobile agent system can be used for electronic commerce as an important key technology. In order to realize such a system, Lee et al. showed that a secure mobile agent can be constructed using proxy signatures. Intuitively, a proxy signature permits an entity (delegator) to delegate its signing right to another entity (proxy) to sign some specified messages on behalf of the delegator. However, the proxy signatures are often used in scenarios where the signing is done in an insecure environment, for example, the remote server of a mobile agent system. In such setting, an adversary could launch side-channel attacks to exploit some leakage information about the proxy key or even other secret states. The proxy signatures which are secure in the traditional security models obviously cannot provide such security. Based on this consideration, in this paper, we design a leakage-resilient proxy signature scheme for the secure mobile agent systems.

Simpler CCA-Secure Public Key Encryption from Lossy Trapdoor Functions

In STOC’08, Peikert and Waters presented a black-box construction of CCA-secure public key encryption (PKE) scheme from lossy trapdoor functions (LTDFs) [20], and they mentioned in the paper that their construction is a hybrid of Naor-Yung [18] and Canetti-Halevi-Katz [5], since the twin encryption technique and a strongly one-time signature are simultaneously used. It is well-known that a one-time signature brings either large ciphertext overhead if built from general assumptions like one-way functions, or additional computation cost during key generation/signing if built from number theoretic assumptions.