Now showing items 331-336 of 336
Expressiveness of Definitions and Efficiency of Constructions in Computational Cryptography
The computational treatment of cryptography, and indeed any scientific treatment of a problem, is marked by its definitional side and by it constructive side. Results in this thesis better our understanding of both: on one side, they characterize the extent to which computational definitions capture the security of the basic task of symmetric encryption; on the other, they provide explicit bounds on the efficiency of commitment and secure two-party computation constructions. Specifically: - We relate the formal and computational treatments of symmetric encryption, obtaining a precise characterization of computational schemes whose computational semantics imply their formal semantics. We prove that this characterization is strictly weaker than previously-identified notions, and show how it may be realized in a simpler, more efficient manner. - We provide lower-bounds on the number of times a one-way permutation needs to be invoked (as a "black-box") in order to construct statistically-binding commitments. Our bounds are tight for the case of perfectly-binding schemes. - We show that the secure computation of any two-party functionality can be performed in an optimal two rounds of communication even in a setting that accounts for concurrent execution with other protocols (i.e., the Universal Composability framework). Here, we rely on the assumption that parties have access to a common reference string; some sort of setup is known to be necessary....
Integrating Statistics and Visualization to Improve Exploratory Social Network Analysis
Social network analysis is emerging as a key technique to understanding social, cultural and economic phenomena. However, social network analysis is inherently complex since analysts must understand every individual's ...
Machine Translation by Pattern Matching
The best systems for machine translation of natural language are based on statistical models learned from data. Conventional representation of a statistical translation model requires substantial offline computation and ...
Using Join Networks to Compute Satisfiability
Satisfiability (SAT) of propositional logic formulas is a canonical NP-complete problem; algorithms for its solution have been studied for over forty years. The representational power of propositional logic allows a host ...
Spatio-Temporal Reasoning About Agent Behavior
There are many applications where we wish to reason about spatio-temporal aspects of an agent's behavior. This dissertation examines several facets of this type of reasoning. First, given a model of past agent behavior, ...
The Great Firewall, Terracotta VPN, and the Social Construction of the Chinese Internet
With almost 722 million active users in 2016, China has become home to one of the largest and fastest growing internet communities in the world. But, due in large part to the restrictive measures by the Chinese Communist ...