Self-Stabilizing Byzantine-Resilient Communication in Dynamic Networks

We consider the problem of communicating reliably in a dynamic network in the presence of up to k Byzantine failures. It was shown that this problem can be solved if and only if the dynamic graph satisfies a certain condition, that we call "RDC condition". In this paper, we present the first self-stabilizing algorithm for reliable communication in this setting - that is: in addition to permanent Byzantine failures, there can also be an arbitrary number of transient failures. We prove the correctness of this algorithm, provided that the RDC condition is "always eventually satisfied"

A theory of normed simulations

In existing simulation proof techniques, a single step in a lower-level specification may be simulated by an extended execution fragment in a higher-level one. As a result, it is cumbersome to mechanize these techniques using general purpose theorem provers. Moreover, it is undecidable whether a given relation is a simulation, even if tautology checking is decidable for the underlying specification logic. This paper introduces various types of normed simulations. In a normed simulation, each step in a lower-level specification can be simulated by at most one step in the higher-level one, for any related pair of states. In earlier work we demonstrated that normed simulations are quite useful as a vehicle for the formalization of refinement proofs via theorem provers. Here we show that normed simulations also have pleasant theoretical properties: (1) under some reasonable assumptions, it is decidable whether a given relation is a normed forward simulation, provided tautology checking is decidable for the underlying logic; (2) at the semantic level, normed forward and backward simulations together form a complete proof method for establishing behavior inclusion, provided that the higher-level specification has finite invisible nondeterminism.Comment: 31 pages, 10figure

Compilation and Equivalence of Imperative Objects (Revised Report)

We adopt the untyped imperative object calculus of Abadi andCardelli as a minimal setting in which to study problems of compilationand program equivalence that arise when compiling object orientedlanguages. We present both a big-step and a small-stepsubstitution-based operational semantics for the calculus. Our firsttwo results are theorems asserting the equivalence of our substitution based semantics with a closure-based semantics like that given by Abadi and Cardelli. Our third result is a direct proof of the correctness of compilation to a stack-based abstract machine via a small-step decompilation algorithm. Our fourth result is that contextual equivalence of objects coincides with a form of Mason and Talcott's CIUequivalence; the latter provides a tractable means of establishing operational equivalences. Finally, we prove correct an algorithm, used inour prototype compiler, for statically resolving method offsets. This isthe first study of correctness of an object-oriented abstract machine,and of operational equivalence for the imperative object calculus

Publications from NIAS: January 1988-June 2013 (NIAS Report No. R23-2014)

This report has a bibliographic listing of all the publications from NIAS since inception till June 201

A Statistical Verification Method of Random Permutations for Hiding Countermeasure Against Side-Channel Attacks

As NIST is putting the final touches on the standardization of PQC (Post Quantum Cryptography) public key algorithms, it is a racing certainty that peskier cryptographic attacks undeterred by those new PQC algorithms will surface. Such a trend in turn will prompt more follow-up studies of attacks and countermeasures. As things stand, from the attackers' perspective, one viable form of attack that can be implemented thereupon is the so-called "side-channel attack". Two best-known countermeasures heralded to be durable against side-channel attacks are: "masking" and "hiding". In that dichotomous picture, of particular note are successful single-trace attacks on some of the NIST's PQC then-candidates, which worked to the detriment of the former: "masking". In this paper, we cast an eye over the latter: "hiding". Hiding proves to be durable against both side-channel attacks and another equally robust type of attacks called "fault injection attacks", and hence is deemed an auspicious countermeasure to be implemented. Mathematically, the hiding method is fundamentally based on random permutations. There has been a cornucopia of studies on generating random permutations. However, those are not tied to implementation of the hiding method. In this paper, we propose a reliable and efficient verification of permutation implementation, through employing Fisher-Yates' shuffling method. We introduce the concept of an n-th order permutation and explain how it can be used to verify that our implementation is more efficient than its previous-gen counterparts for hiding countermeasures.Comment: 29 pages, 6 figure

Digital Image Users and Reuse: Enhancing practitioner discoverability of digital library reuse based on user file naming behavior

Diese Dissertation untersucht Geräte, die Praktiker verwenden, um die Wiederverwendung von digitalen Bibliotheksmaterialien zu entdecken. Der Autor führt zwei Verifikationsstudien durch, in denen zwei zuvor angewandte Strategien untersucht werden, die Praktiker verwenden, um die Wiederverwendung digitaler Objekte zu identifizieren, insbesondere Google Images Reverse Image Lookup (RIL) und eingebettete Metadaten. Es beschreibt diese Strategiebeschränkungen und bietet einen neuen, einzigartigen Ansatz zur Verfolgung der Wiederverwendung, indem der Suchansatz des Autors basierend auf dem Benennungsverhalten von Benutzerdateien verwendet wird. Bei der Untersuchung des Nutzens und der Einschränkungen von Google Images und eingebetteten Metadaten beobachtet und dokumentiert der Autor ein Muster des Benennungsverhaltens von Benutzerdateien, das vielversprechend ist, die Wiederverwendung durch den Praktiker zu verbessern. Der Autor führt eine Untersuchung zur Bewertung der Dateibenennung durch, um dieses Muster des Verhaltens der Benutzerdateibenennung und die Auswirkungen der Dateibenennung auf die Suchmaschinenoptimierung zu untersuchen. Der Autor leitet mehrere signifikante Ergebnisse ab, während er diese Studie fertigstellt. Der Autor stellt fest, dass Google Bilder aufgrund der Änderung des Algorithmus kein brauchbares Werkzeug mehr ist, um die Wiederverwendung durch die breite Öffentlichkeit oder andere Benutzer zu entdecken, mit Ausnahme von Benutzern aus der Industrie. Eingebettete Metadaten sind aufgrund der nicht persistenten Natur eingebetteter Metadaten kein zuverlässiges Bewertungsinstrument. Der Autor stellt fest, dass viele Benutzer ihre eigenen Dateinamen generieren, die beim Speichern und Teilen von digitalen Bildern fast ausschließlich für Menschen lesbar sind. Der Autor argumentiert, dass, wenn Praktiker Suchbegriffe nach den "aggregierten Dateinamen" modellieren, sie ihre Entdeckung wiederverwendeter digitaler Objekte erhöhen.This dissertation explores devices practitioners utilize to discover the reuse of digital library materials. The author performs two verification studies investigating two previously employed strategies that practitioners use to identify digital object reuse, specifically Google Images reverse image lookup (RIL) and embedded metadata. It describes these strategy limitations and offers a new, unique approach for tracking reuse by employing the author's search approach based on user file naming behavior. While exploring the utility and limitations of Google Images and embedded metadata, the author observes and documents a pattern of user file naming behavior that exhibits promise for improving practitioner's discoverability of reuse. The author conducts a file naming assessment investigation to examine this pattern of user file naming behavior and the impact of file naming on search engine optimization. The author derives several significant findings while completing this study. The author establishes that Google Images is no longer a viable tool to discover reuse by the general public or other users except for industry users because of its algorithm change. Embedded metadata is not a reliable assessment tool because of the non-persistent nature of embedded metadata. The author finds that many users generate their own file names, almost exclusively human-readable when saving and sharing digital images. The author argues that when practitioners model search terms after the "aggregated file names" they increase their discovery of reused digital objects

Linguistically-Informed Neural Architectures for Lexical, Syntactic and Semantic Tasks in Sanskrit

The primary focus of this thesis is to make Sanskrit manuscripts more accessible to the end-users through natural language technologies. The morphological richness, compounding, free word orderliness, and low-resource nature of Sanskrit pose significant challenges for developing deep learning solutions. We identify four fundamental tasks, which are crucial for developing a robust NLP technology for Sanskrit: word segmentation, dependency parsing, compound type identification, and poetry analysis. The first task, Sanskrit Word Segmentation (SWS), is a fundamental text processing task for any other downstream applications. However, it is challenging due to the sandhi phenomenon that modifies characters at word boundaries. Similarly, the existing dependency parsing approaches struggle with morphologically rich and low-resource languages like Sanskrit. Compound type identification is also challenging for Sanskrit due to the context-sensitive semantic relation between components. All these challenges result in sub-optimal performance in NLP applications like question answering and machine translation. Finally, Sanskrit poetry has not been extensively studied in computational linguistics. While addressing these challenges, this thesis makes various contributions: (1) The thesis proposes linguistically-informed neural architectures for these tasks. (2) We showcase the interpretability and multilingual extension of the proposed systems. (3) Our proposed systems report state-of-the-art performance. (4) Finally, we present a neural toolkit named SanskritShala, a web-based application that provides real-time analysis of input for various NLP tasks. Overall, this thesis contributes to making Sanskrit manuscripts more accessible by developing robust NLP technology and releasing various resources, datasets, and web-based toolkit.Comment: Ph.D. dissertatio

Rockefeller Foundation - 1997 Annual Report

Contains statement of mission and vision, president's message, program information, grants list, financial statements, and list of board members and staff

Brain Drain or Gain: Migration of Knowledge Workers From India to the United States

This dissertation looks at the topic of brain drain from a new lens. It departs from the traditional literature to include discussion on brain gain and brain circulation using Indian migration to the United States as case study. While it cannot be denied that host countries have policies that encourage or provide the necessary conditions for brain drain to take place, it must be taken into account that many source countries now benefit from out-migration of their workers and students. These are usually measured as remittances, investments and savings associated with return, and network approaches that, with a connectionist approach, link expatriates with their country of origin. In addition, Diaspora members, through successes and visibility in host societies, further influence economic and political benefits for their home countries. This type of brain gain can be considered as element of soft power for the source country in the long term. Three hypotheses are tested in this dissertation to argue the points above. Using India as source country, the first hypothesis positively tested that benefits outweigh the cost of out-migration, with India as the highest remittance receiving country in the world with multifaceted connections in the Silicon Valley. The second hypothesis accessed the leverage of the Indo-American community as strong in terms of wealth and education. However, the possibility of this changing the asymmetrical interdependent relationship between India and the U.S. in favor of India remains at best a possibility in the long term. The third hypothesis also positively tested that a more active role played by the state in the sending country determines the level of return and non-return benefits. The dissertation also notes that while these hypotheses may be true for a country like India, where many other factors play a role, it may not necessarily affect other less developing countries in a similar vein. Additionally, third generation Indo-Americans may not necessarily retain the same ties as were seen by the first and second generations. Thus direct benefits in the long term may differ in result