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Computer Sciences

Dartmouth College

Dartmouth College Undergraduate Theses

2006

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Wait-Free And Obstruction-Free Snapshot, Khanh Do Ba Jun 2006

Wait-Free And Obstruction-Free Snapshot, Khanh Do Ba

Dartmouth College Undergraduate Theses

The snapshot problem was first proposed over a decade ago and has since been well-studied in the distributed algorithms community. The challenge is to design a data structure consisting of $m$ components, shared by upto $n$ concurrent processes, that supports two operations. The first, $Update(i,v)$, atomically writes $v$ to the $i$th component. The second, $Scan()$, returns an atomic snapshot of all $m$ components. We consider two termination properties: wait-freedom, which requires a process to always terminate in a bounded number of its own steps, and the weaker obstruction-freedom, which requires such termination only for processes that eventually execute uninterrupted. First, …


Limited Delegation (Without Sharing Secrets) In Web Applications, Nicholas J. Santos May 2006

Limited Delegation (Without Sharing Secrets) In Web Applications, Nicholas J. Santos

Dartmouth College Undergraduate Theses

Delegation is the process wherein an entity Alice designates an entity Bob to speak on her behalf. In password-based security systems, delegation is easy: Alice gives Bob her password. This is a useful feature, and is used often in the real world. But it's also problematic. When Alice shares her password, she must delegate all her permissions, but she may wish to delegate a limited set. Also, as we move towards PKI-based systems, secret-sharing becomes impractical. This thesis explores one solution to these problems. We use proxy certificates in a non-standard way so that user Alice can delegate a subset …