Further discussions on the security of a nominative signature scheme

A nominative signature scheme allows a nominator (or signer) and a nominee (or veri¯er) to jointly generate and publish a signature in such a way that only the nominee can verify the signature and if nec- essary, only the nominee can prove to a third party that the signature is valid. In a recent work, Huang and Wang proposed a new nominative signature scheme which, in addition to the above properties, only allows the nominee to convert a nominative signature to a publicly veri¯able one. In ACISP 2005, Susilo and Mu presented several algorithms and claimed that these algorithms can be used by the nominator to verify the validity of a published nominative signature, show to a third party that the signature is valid, and also convert the signature to a publicly veri¯able one, all without any help from the nominee. In this paper, we point out that Susilo and Mu\u27s attacks are actually incomplete and in- accurate. In particular, we show that there exists no e±cient algorithm for a nominator to check the validity of a signature if this signature is generated by the nominator and the nominee honestly and the Decisional Di±e-Hellman Problem is hard. On the other hand, we point out that the Huang-Wang scheme is indeed insecure, since there is an attack that allows the nominator to generate valid nominative signatures alone and prove the validity of such signatures to a third party

End-to-End QoS Support for a Medical Grid Service Infrastructure

Quality of Service support is an important prerequisite for the adoption of Grid technologies for medical applications. The GEMSS Grid infrastructure addressed this issue by offering end-to-end QoS in the form of explicit timeliness guarantees for compute-intensive medical simulation services. Within GEMSS, parallel applications installed on clusters or other HPC hardware may be exposed as QoS-aware Grid services for which clients may dynamically negotiate QoS constraints with respect to response time and price using Service Level Agreements. The GEMSS infrastructure and middleware is based on standard Web services technology and relies on a reservation based approach to QoS coupled with application specific performance models. In this paper we present an overview of the GEMSS infrastructure, describe the available QoS and security mechanisms, and demonstrate the effectiveness of our methods with a Grid-enabled medical imaging service

Nominative Proxy Signature Schemes

In a nominative proxy signature scheme, an original singer delegates his signing power to a proxy, who generates a nominative signature on behalf of the original signer. In a nominative proxy signature scheme, only the nominee can verify the signature and if necessary, only the nominee can prove its validity to the third party. In this paper, we first classify the nominative proxy signature into two types, original-nominative proxy signature and proxy-nominative proxy signature. Then we analyze the nominative proxy scheme proposed by Park and Lee. We show that the scheme suffers from universal verification. We also point out that the scheme presented by S.-H. Seo and S.-H. Lee is insecure and the scheme cannot provide non-repudiation. Finally we present our nominative proxy signature schemes which overcome the weakness mentioned above. Compared with the scheme recently proposed by G.-L. Wang, our scheme is more efficient

Efficient Construction of Nominative Signature Secure under Symmetric Key Primitives and Standard Assumptions on Lattice

Nominative signature is a cryptographic primitive where two parties collude to produce a signature. It is a user certification system and has applications in variety of sectors where nominee cannot trust heavily on the nominator to validate nominee’s certificate and only targeted entities are allowed to verify signature on sensitive data. We provide a new construction for nominative signature from standard assumptions on lattice. Our construction relies on collision resistant preimage sampleable function and symmetric key primitives like collision resistant pseudorandom function and zero knowledge proof system ZKB++ for Boolean circuits. We provide a detailed security analysis and show that our construction achieves security under unforgeability, invisibility, impersonation and non-repudiation in existing model. Furthermore, our construction exhibits non-transferability. The security under non-repudiation is achieved in the quantum random oracle model using Unruh transform to ZKB++

Technological Developments in Legal Research

Technology has created new types of legal research and means of access to the law. Specific to appellate practice, technology has changed how decisions are published and the nature of legal research. Technology has even created a debate on who owns the different forms of case law

Technological Developments in Legal Research

Technology has created new types of legal research and means of access to the law. Specific to appellate practice, technology has changed how decisions are published and the nature of legal research. Technology has even created a debate on who owns the different forms of case law

Classification of Signature-only Signature Models

We introduce a set of criterions for classifying signature-only signature models. By the criterions, we classify signature models into 5 basic types and 69 general classes. Theoretically, 21140 kinds of signature models can be deduced by appropriately combining different general classes. The result comprises almost existing signature models. We also contribute a lot of new signature models. Moreover, we find the three signature models, i.e., group-nominee signature, multi-nominee signature and threshold-nominee signature, are of great importance in light of our classification