Verifier-Local Revocation Group Signature Schemes Research Articles

Almost Fully Secured Lattice-Based Group Signatures with Verifier-Local Revocation

An efficient member revocation mechanism is a desirable feature when group signature schemes are applied in practical scenarios. Revocation methods, such as verifier-local revocation (VLR), provide an efficient member revocation in applications of group signatures. However, VLR-group signatures rely on a weaker security notion. On the other hand, group signature schemes for static groups gain stronger security with the full-anonymity security notion. Even though an outsider sees the secret signing keys of all group members in the full-anonymity, the signer is still anonymous. Achieving the full-anonymity for VLR group signature schemes is challenging due to the structure of secret signing keys. The secret signing keys of those schemes consist of tokens, which are used to manage revocation. The reveal of tokens may destroy the anonymity of the signers. We obtain stronger security for the lattice-based VLR group signature schemes by providing a new key generation method, which outputs revocation tokens without deriving from the members’ secret signing keys. We propose a new group signature scheme from lattices with VLR, which achieves stronger security than the previous related works. To avoid signature forgeries, we suggest a new zero-knowledge proof system that requires signers to validate themselves. Moreover, we output an efficient tracing mechanism.

Publicly Verifiable Shared Dynamic Electronic Health Record Databases With Functional Commitment Supporting Privacy-Preserving Integrity Auditing

Electronic health record (EHR) is a system that collects patients' digital health information and shares it with other healthcare providers in the cloud. Since EHR contains a large amount of significant and sensitive information about patients, it is required that the system ensures response correctness and storage integrity. Meanwhile, with the rise of IoT, more low-performance terminals are deployed for receiving and uploading patient data to the server, which increases the computational and communication burden of the EHR systems. The verifiable database (VDB), where a user outsources his large database to a cloud server and makes queries once he needs certain data, is proposed as an efficient updatable cloud storage model for resource-constrained users. To improve efficiency, most existing VDB schemes utilize proof reuse and proof updating technique to prove correctness of the query results. However, it ignores the “real-time” of proof generation, which results in an overhead that the user has to perform extra process (e.g., auditing schemes) to check storage integrity. In this article, we propose a publicly verifiable shared updatable EHR database scheme that supports privacy-preserving and batch integrity checking with minimum user communication cost. We modify the existing functional commitment (FC) scheme for the VDB design and construct a concrete FC under the computational <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> -BDHE assumption. In addition, the use of an efficient verifier-local revocation group signature scheme makes our scheme support dynamic group member operations, and gives nice features, such as traceability and non-frameability.

Lattice-based group signature with verifier-local revocation

Among several post quantum primitives proposed in the past few decades, lattice-based cryptography is considered as the most promising one, due to its underlying rich combinatorial structure, and the worst-case to average-case reductions. The first lattice-based group signature scheme with verifier-local revocation (VLR) is treated as the first quantum-resistant scheme supported member revocation, and was put forward by Langlois et al. This VLR group signature (VLR-GS) has group public key size of O(nm log N log q), and a signature size of O(tm logN log q log β). Nguyen et al. constructed a simple efficient group signature from lattice, with significant advantages in bit-size of both the group public key and the signature. Based on their work, we present a VLR-GS scheme with group public key size of O(nm log q) and signature size of O(tm log q). Our group signature has notable advantages: support of membership revocation, and short in both the public key size and the signature size.

More Efficient VLR Group Signature Based on DTDH Assumption

In VLR (verifier-local revocation) group signature, only verifiers are involved in the revocation of a member, while signers are not. Thus the VLR group signature schemes are suitable for mobile environments. To meet the requirement of speediness, reducing computation costs and shortening signature length are two requirements at the current research of VLR group signatures. A new VLR group signature is proposed based on q-SDH assumption and DTDH assumption. Compared with the existing VLR group signatures based on DTDH assumption, the proposed scheme not only has the shortest signature size, but also has the lowest computation costs , and can be applicable to mobile environments such as IEEE 802.1x. DOI: http://dx.doi.org/10.11591/telkomnika.v10i6.1428 Full Text: PDF

Improved VLR Group Signature Based on DTDH Assumption

In VLR (verifier-local revocation) group signatures, revocation messages are only sent to signature verifiers (as opposed to both signers and verifiers). Consequently there is no need to contact individual signers when some user is revoked. Since signers have no load, the VLR group signature schemes are suitable for mobile environments. To meet the requirement of speediness in mobile communication, reducing computation costs and shortening signature length are two requirements at the current research of VLR group signatures. Based on this idea, an improved version of Zhou’s VLR group signature is given. Compared with the original scheme, the improved scheme not only can achieve the same security level, but also has shorter signature size and lower computation costs.

Backward Unlinkability and Verifier-Local Revocation Group Signature Scheme with Lower Cost

In the current group signature schemes with backward unlinkability and verifier-local revocation (BU-VLR), the size of the public key is linear with the total number of time intervals, and the size of the revocation list (RL) is linear with the total number of time intervals and revoked members. Therefore, the cost is high not only in memory space but also in revocation token computation and revocation check. This paper proposes a BU-VLR group signature scheme under the DTDH assumption and the q-SDH assumption, which has short public key and RL to reduce the overheads in previous schemes. Moreover, it also has shorter signature length and smaller computation in signing.

Verifier-Local Revocation Group Signature Schemes with Backward Unlinkability from Bilinear Maps

An approach of membership revocation in group signatures is verifier-local revocation (VLR for short). In this approach, only verifiers are involved in the revocation mechanism, while signers have no involvement. Thus, since signers have no load, this approach is suitable for mobile environments. Although Boneh and Shacham recently proposed a VLR group signature scheme from bilinear maps, this scheme does not satisfy the backward unlikability. The backward unlinkability means that even after a member is revoked, signatures produced by the member before the revocation remain anonymous. In this paper, we propose VLR group signature schemes with the backward unlinkability from bilinear maps.