Refuge Update Article Index

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Refuge Update – November/December 2009, Volume 6, Number 6

Table of Contents: Tufted Puffin Released A rehabilitated puffin gingerly tests freedom at Oregon Islands National Wildlife Refuge. FOCUS: Stories of Hope From cemeteries to woodpeckers, to newspaper columns and support at the ballot box, refuges represent stories of hope as they pursue their mission. Bats in the Barn Scientists and volunteers wrap a barn in plastic and count the bats inside. Sense of Wonder Award Jim Burkhart shares the joy and mysteries of the natural world with visitors to Okefenokee National Wildlife Refuge, GA.

Hierarchy-Based Access Control in Distributed Environments

Access control is a fundamental concern in any system that manages resources, e.g., operating systems, file systems, databases and communications systems. The problem we address is how to specify, enforce, and implement access control in distributed environments. This problem occurs in many applications such as management of distributed project resources, e-newspaper and payTV subscription services. Starting from an access relation between users and resources, we derive a user hierarchy, a resource hierarchy, and a unified hierarchy. The unified hierarchy is then used to specify the access relation in a way that is compact and that allows efficient queries. It is also used in cryptographic schemes that enforce the access relation. We introduce three specific cryptography based hierarchical schemes, which can effectively enforce and implement access control and are designed for distributed environments because they do not need the presence of a central authority (except perhaps for set- UP).

Agriculture Builders of Nebraska Inc.

It’s a pleasure to be able to speak with you today. I want you to know that Virginia and I are delighted to be in Nebraska. And I’m especially happy to have arrived in the state at a time where I can, on my 7th day on the job, learn so much about UNL just by reading the state’s largest newspaper.

RURALS 1008: Title of another article

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