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One-way hash chains have been the preferred choice, over the symmetric and asymmetric key cryptography, in security setups where efficiency mattered; despite the ephemeral confidentiality and authentication they assure. Known constructions of one-way chains (for example, SHA-1 based), only ensure the forward secrecy and have limitations over their length(More)
One-way hash chains have been the preferred choice (over symmetric and asymmetric key cryptography) in security setups where efficiency mattered; despite the ephemeral confidentiality and authentication they assure. They only support forward secrecy and have limitations over the chain size (bounded). In this paper, we show how the use of chameleon functions(More)
There has been an enormous increase of transactions and cooperative-computing services on the Internet. This is both a technical and a social phenomenon. Transactions and services over the Internet have global reach and users, known or unknown to the service provider, might be interested in availing the access or participate in the cooperative transaction(More)
In this paper, we propose a new efficient and secure micro-payment scheme, named e-coupons, which can provide the users the facility of delegating their spending capability to other users or their own devices like Laptop, PDA, Mobile Phone, and such service access points. The scheme has the promise of becoming an enabler for various Internet-based services(More)
Security over the Internet depends on a clear distinction between authorized and unauthorized principals. Discriminating between the two involves: identification (user identifies himself/herself), authentication (the system validates the user's identity) and authorization (specific rights granted). Thus, it is important to develop specifications for access(More)
Access control models need to be interoperable when administrative domains with heterogeneous access control models need to collaborate. Even, collaboration among homogeneous access control models is not straight-forward due to the different security orderings they might employ. In this paper, we briefly put forward an overlay formation mechanism based on(More)
BACKGROUND AND OBJECTIVE Restoration of carious lesions with a strong permanent bond would be a highly desirable requisite. Ultra morphological characterization shows that observing and understanding the interfacial phenomenon and its quality would be of great importance in the selection of a dental adhesive for its use in pediatric restorative dentistry.(More)
Collaboration among independent administrative domains would require: i) confidentiality, integrity, non-repudiation of communication between the domains; ii) minimum and reversible modifications to the intra-domain pre-collaboration setup; iii) maintain functional autonomy while collaborating; and, iv) ability to quickly transform from post-collaboration(More)
In this paper, we describe the design and implementation of ROADS; a role-based authorization and delegation system, based on a simple distributed security infrastructure called SPKI/SDSI [1]. We have developed a flexible access control mechanism called FLEXI-ACL that allows us to enforce different kinds of authenti-cation schemes so that it becomes easy(More)