Lihua Wang, Jun Shao, Zhenfu Cao, Masahiro Mambo, Akihiro Yamamura, and Licheng Wang, "Certificate-Based Proxy Decryption Systems with Revocability in the Standard Model," Information Science, 247:188-201 (2013) AbstractPaper Issue2
We present the concept of a certificate-based proxy decryption (CBPd) system with revocability, which has the following properties: (1) key-escrow freeness, (2) implicit certification, (3) revocability without public key change, and (4) fine-grained delegation. A concrete CBPd scheme is also proposed. The scheme is semantically secure against adaptive chosen plaintext attack (IND-CBPd-Rev-CPA) under the decisional bilinear Diffie-Hellman assumption in the standard model. We also give an enhanced scheme that is secure against adaptive chosen-ciphertext attacks (INDCBPd-Rev-CCA) in the standard model.
Yuanju Gan, Lihua Wang, Licheng Wang, Ping Pan and Yixian Yang, "Efficient Construction of CCA-Secure Threshold PKE Based on Hashed Diffie-Hellman Assumption," The computer Journal, 56(10):1249-1257 (2013) AbstractPaper Issue2
In threshold public-key encryption (TPKE), the decryption key is divided into n shares, each one of which is given to a different decryption user in order to avoid single points of failure. A robust TPKE is one that, when the threshold decryption of a valid ciphertext fails, allows the combiner to identify the decryption users that supplied invalid partial decryption shares. In this paper, we propose a practical and efficient TPKE scheme which is robust and non-interactive. Security against chosen-ciphertext attacks (CCAs) can be proved in the standard model under the Hashed Diffie-Hellman assumption in bilinear groups. The security reduction is tight and simple. We use both an instantiation hash function of the Kiltz's key encapsulation mechanism and Lai et al.'s chosen-ciphertext secure technique to construct a TPKE scheme. Moreover, our scheme is simpler and has proven to be more efficient than currently existing CCA-secure TPKE schemes.
Yuanju Gan, Lihua Wang, Licheng Wang, Ping Pan, and Yixian Yang, “Efficient Threshold PKE with Full Security Based on Dual Pairing Vector Spaces”, International Journal of Communication Systems (2013) AbstractPaper Issue2
Most robust and non-interactive threshold public-key encryption (PKE) schemes have only been proven secure against chosen-ciphertext attacks under the static corruption model; yet the dynamic corruption model is more reasonable. In this paper, based on bilinear groups of prime order and dual pairing vector spaces, we propose a threshold PKE scheme that is non-interactive, robust and secure against adaptive chosen-ciphertext attacks under the dynamic corruption model without random oracles. Moreover, our scheme is shown to be more efficient than currently existing fully secure threshold PKE schemes.
Tanaka Hidema，Lihua Wang，Ryuichi Ichikawa, Tukasa Iwama, and Yasuhiro Koyama，"Position Authentication Using Homomorphic Encryption," IEICE, J96-D(8): 1913-1924 (2013) AbstractPaper Issue2
Applications and services that use position information, such as pinpointing of the source of information dissemination, physical distribution, etc., are widespread. The position information used now is based on a user’s self-assessment and can detect neither false statements nor spoofing. To solve these problems, we propose two position information authentication protocols in which spoofing, illegal uses, and falsifying of position information are detectable by using homomorphic encryption techniques on data acquired from either quasi-zenith satellites or terrestrial waves.
Ping Pan, Licheng Wang, Yuanju Gan, and Yixian Yang, Lihua Wang, "Chameleon Hash Functions and One-Time Signature Schemes from Inner Automorphism Groups," Fundamental Informaticae, 126: 103-119 (2013) AbstractPaper Issue1
In this paper, we build a family of chameleon hash functions and strongly unforgeable one-time signature schemes based on the intractability assumption of the discrete logarithm problem (DLP) over inner automorphism groups. Since the DLP assumption over inner automorphism groups does not admit sub-exponential attacks, the sizes of the working parameters used in our constructions are shortened significantly. This leads to remarkable gains for our proposals both in running time and storage space. In addition, as far as we know, this is the first time CHF and OTS were built based on non-commutative groups.
Jianhua Yan, Licheng Wang, Lihua Wang, Yixian Yang, Wenbin Yao. “Efficient Lattice-Based Signcryption in Standard Model”，Mathematical Problems in Engineering (2013) AbstractPaper Issue1
Signcryption is a cryptographic primitive that can perform digital signature and public encryption simultaneously at a significantly reduced cost. This advantage makes it highly useful for many applications. However, most existing signcryption schemes are seriously challenged by the booming of quantum computations. As an interesting stepping stone in the post-quantum cryptographic community, two lattice-based signcryption schemes were proposed recently. But both of them were merely proved to be secure in the random oracle models. Therefore, the main contribution of this paper is to propose a new lattice-based signcryption scheme that can be proved to be secure for the standard model.
Yuanju Gan, Lihua Wang, Licheng Wang, Ping Pan and Yixian Yang, "Publicly Verifiable Secret Sharing Scheme with Provable SecurityAgainst Chosen Secret Attacks," International Journal of Distributed Sensor Networks (2013). AbstractPaper Issue2
Secret sharing is an important aspect of key management in wireless ad hoc and sensor networks. In this paper, we define a new secure model of secret sharing, using the Lagrange interpolation and the bilinear cyclic groups to construct an efficient publicly verifiable secret sharing scheme on the basis of this model, and show that this scheme is provably secure against adaptively chosen secret attacks (CSAs) based on the decisional bilinear Diffie-Hellman (DBDH) problem. We find that this scheme has the following properties: (a) point-to-point secure channels are not required in both the secret distribution phase and the secret reconstruction phase, (b) it is a non-interactive secret sharing system in that the participants need not communicate with each other during sub-shadow verification, and (c) each participant is able to share many secrets with other participants despite holding only one shadow.
Lihua Wang, Lichen Wang, Masahiro Mambo, and Eiji Okamoto, "Identity-Based Proxy Cryptosystems with Revocability and Hierarchical Confidentialities," IEICE Transaction on Fundamentals, E95-A(1):70-88 (2012) AbstractPaper Issue2
We propose an ID-based proxy cryptosystem with revocability and hierarchical confidentialities in which, on receiving a ciphertext, the proxy has the right to perform the following three tasks according to the message confidentiality levels of the sender's intention: (1) to decrypt the ciphertext on behalf of the original decryptor; (2) to re-encrypt the ciphertext such that another user who is designated by the original decryptor can learn the message; and (3) to do nothing except for forwarding the ciphertext to the original decryptor. Our scheme supports revocability in the sense that it allows the proxy’s decryption and re-encryption rights to be revoked even during the valid period of the proxy key without changing the original decryptor's public information. We prove that our proposal is indistinguishable against chosen identity and plaintext attacks in the standard model. We also show how to convert it into a system with security against chosen identity and ciphertext attacks by using the Fujisaki-Okamoto transformation.
Ping Pan, Lihua Wang, Licheng Wang, Lixiang Li, and Yixian Yang, "CSP-DHIES: A New Public-Key Encryption Scheme From Matrix Conjugation," Security and Communication Networks, 5(7): 809–822 (2012) AbstractPaper Issue1
We propose a new public-key cryptosystem named the conjugacy search problem-based Diffie-Hellman integrated encryption scheme (CSP-DHIES) as the first non-communicative variant of the well-known DHIES cryptosystem. Under the assumption of the intractability of the CSP-based oracle Diffie-Hellman problem, our scheme is proven to be secure against chosen-ciphertext attacks in the standard model. We also discuss the possibility of implementing our proposal using braid groups.
Proxy re-encryption (PRE) is a highly useful cryptographic primitive whereby Alice and Bob can endow a proxy with the capacity to change ciphertext recipients from Alice to Bob, without the proxy itself being able to decrypt, thereby providing delegation of decryption authority.
Key-private PRE (KP-PRE) specifies an additional level of confidentiality, requiring pseudo-random proxy keys that leak no information on the identity of the delegators and delegatees.
In this paper, we propose a CPA-secure PK-PRE scheme in the standard model (which we then transform into a CCA-secure scheme in the random oracle model). Both schemes enjoy highly desirable properties such as uni-directionality and multi-hop delegation.
Unlike (the few) prior constructions of PRE and KP-PRE that typically rely on bilinear maps under ad hoc assumptions, security of our construction is based on the hardness of the standard Learning-With-Errors (LWE) problem, itself reducible from worst-case lattice hard problems that are conjectured immune to quantum cryptanalysis, or “post-quantum”.
Of independent interest, we further examine the practical hardness of the LWE assumption, using Kannan’s exhaustive search algorithm coupling with pruning techniques. This leads to state-of-the-art parameters not only for our scheme, but also for a number of other primitives based on LWE published the literature
Symposium Presented Papers
Lihua Wang, Atsushi Waseda, Ryo Nojima, and Shiho Moriai, "PRINCESS: Proxy Re-encryption with INd-Cca security in Encrypted file Storage System," SCIS2014. AbstractPaper Issue2
In many present cloud storage systems, files are uploaded to the storage server in plaintext. When the server suffers intrusion, the storage data becomes insecure. One of the existing methods to solve this problem proposes the uploading of encrypted data to the server. However, there remains the issue of data exchange. One solution, the use of proxy re-encryption technology, would make encrypted file exchange possible. In this paper, we introduce a secure file storage system based on Wang et al.’s proxy cryptosystem with revocability, which can realize encrypted file exchange at three confidential levels.
Lihua Wang, "Study on CSP-based Cryptography," Algebraic Systems and Theoretical Computer Science, Feb. 2012. Abstract Issue1
In this talk, we first recall a proposal based on Grigoriev and Shpilrain’s suggestion under a basic assumption that the CSP problem over some monoid G is intractable. Next, we introduce definitions of the CSP-based computational Diffie-Hellman problem, the CSP-based decisional Diffie-Hellman problem, etc. Then, we describe some encryption schemes that can be proven IND-CCA secure under the above assumptions in the random oracle model. Finally, we show how to fix a mathematical platform in which the above assumptions hold.
Yuanju Gan, Lihua Wang, Ping Pan, Licheng Wang, and Yixian Yang,
"A CCA Secure Threshold KEM Scheme,"
SCIS2012. AbstractPaper Issue2
Based on the bilinear groups with composite order, we propose a threshold Key Encapsulation Mechanism (KEM) scheme that is provably secure in the standard model. We use a direct construction from Boyen-Mei-Waters’ KEM scheme to obtain a threshold KEM scheme that can withstand adaptively chosen-ciphertext attacks (CCA) and adaptive corruption attacks. Moreover, to achieve a higher security level, our construction does not increase additional computation overall.
Lihua Wang, Hidema Tanaka, Ryuichi Ichikawa, Tukasa Iwama, and Yasuhiro Koyama, "Position Information Authentication Using Electric Waves," SITA2011. AbstractPaper Issue2
The application and service using position information, such as pinpointing of the source of information dissemination, physical distribution, etc. are seen plentifully. The position information used now is based on user's self-assessment, and can detect neither a false statement nor spoofing. In this study, by using the homomorphic encryption techniques to the data acquired from the terrestrial wave, we propose a position information authentication protocol that spoofing, illegal uses and falsifying of position information are detectable.