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Reproducibility and Pseudo-Determinism in Log-Space
Reproducibility and Pseudo-determinism in Log-Space by Ofer Grossman S.B., Massachusetts Institute of Technology (2017) Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering and Computer Science at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY May 2020 c Massachusetts Institute of Technology 2020. All rights reserved. Author...................................................................... Department of Electrical Engineering and Computer Science May 15, 2020 Certified by.................................................................. Shafi Goldwasser RSA Professor of Electrical Engineering and Computer Science Thesis Supervisor Accepted by................................................................. Leslie A. Kolodziejski Professor of Electrical Engineering and Computer Science Chair, Department Committee on Graduate Students 2 Reproducibility and Pseudo-determinism in Log-Space by Ofer Grossman Submitted to the Department of Electrical Engineering and Computer Science on May 15, 2020, in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering and Computer Science Abstract Acuriouspropertyofrandomizedlog-spacesearchalgorithmsisthattheiroutputsareoften longer than their workspace. This leads to the question: how can we reproduce the results of a randomized log space computation without storing the output or randomness verbatim? Running the algorithm again with new -
The Next Digital Decade Essays on the Future of the Internet
THE NEXT DIGITAL DECADE ESSAYS ON THE FUTURE OF THE INTERNET Edited by Berin Szoka & Adam Marcus THE NEXT DIGITAL DECADE ESSAYS ON THE FUTURE OF THE INTERNET Edited by Berin Szoka & Adam Marcus NextDigitalDecade.com TechFreedom techfreedom.org Washington, D.C. This work was published by TechFreedom (TechFreedom.org), a non-profit public policy think tank based in Washington, D.C. TechFreedom’s mission is to unleash the progress of technology that improves the human condition and expands individual capacity to choose. We gratefully acknowledge the generous and unconditional support for this project provided by VeriSign, Inc. More information about this book is available at NextDigitalDecade.com ISBN 978-1-4357-6786-7 © 2010 by TechFreedom, Washington, D.C. This work is licensed under the Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA. Cover Designed by Jeff Fielding. THE NEXT DIGITAL DECADE: ESSAYS ON THE FUTURE OF THE INTERNET 3 TABLE OF CONTENTS Foreword 7 Berin Szoka 25 Years After .COM: Ten Questions 9 Berin Szoka Contributors 29 Part I: The Big Picture & New Frameworks CHAPTER 1: The Internet’s Impact on Culture & Society: Good or Bad? 49 Why We Must Resist the Temptation of Web 2.0 51 Andrew Keen The Case for Internet Optimism, Part 1: Saving the Net from Its Detractors 57 Adam Thierer CHAPTER 2: Is the Generative -
FOCS 2005 Program SUNDAY October 23, 2005
FOCS 2005 Program SUNDAY October 23, 2005 Talks in Grand Ballroom, 17th floor Session 1: 8:50am – 10:10am Chair: Eva´ Tardos 8:50 Agnostically Learning Halfspaces Adam Kalai, Adam Klivans, Yishay Mansour and Rocco Servedio 9:10 Noise stability of functions with low influences: invari- ance and optimality The 46th Annual IEEE Symposium on Elchanan Mossel, Ryan O’Donnell and Krzysztof Foundations of Computer Science Oleszkiewicz October 22-25, 2005 Omni William Penn Hotel, 9:30 Every decision tree has an influential variable Pittsburgh, PA Ryan O’Donnell, Michael Saks, Oded Schramm and Rocco Servedio Sponsored by the IEEE Computer Society Technical Committee on Mathematical Foundations of Computing 9:50 Lower Bounds for the Noisy Broadcast Problem In cooperation with ACM SIGACT Navin Goyal, Guy Kindler and Michael Saks Break 10:10am – 10:30am FOCS ’05 gratefully acknowledges financial support from Microsoft Research, Yahoo! Research, and the CMU Aladdin center Session 2: 10:30am – 12:10pm Chair: Satish Rao SATURDAY October 22, 2005 10:30 The Unique Games Conjecture, Integrality Gap for Cut Problems and Embeddability of Negative Type Metrics Tutorials held at CMU University Center into `1 [Best paper award] Reception at Omni William Penn Hotel, Monongahela Room, Subhash Khot and Nisheeth Vishnoi 17th floor 10:50 The Closest Substring problem with small distances Tutorial 1: 1:30pm – 3:30pm Daniel Marx (McConomy Auditorium) Chair: Irit Dinur 11:10 Fitting tree metrics: Hierarchical clustering and Phy- logeny Subhash Khot Nir Ailon and Moses Charikar On the Unique Games Conjecture 11:30 Metric Embeddings with Relaxed Guarantees Break 3:30pm – 4:00pm Ittai Abraham, Yair Bartal, T-H. -
The Flajolet-Martin Sketch Itself Preserves Differential Privacy: Private Counting with Minimal Space
The Flajolet-Martin Sketch Itself Preserves Differential Privacy: Private Counting with Minimal Space Adam Smith Shuang Song Abhradeep Thakurta Boston University Google Research, Brain Team Google Research, Brain Team [email protected] [email protected] [email protected] Abstract We revisit the problem of counting the number of distinct elements F0(D) in a data stream D, over a domain [u]. We propose an ("; δ)-differentially private algorithm that approximates F0(D) within a factor of (1 ± γ), and with additive error of p O( ln(1/δ)="), using space O(ln(ln(u)/γ)/γ2). We improve on the prior work at least quadratically and up to exponentially, in terms of both space and additive p error. Our additive error guarantee is optimal up to a factor of O( ln(1/δ)), n ln(u) 1 o and the space bound is optimal up to a factor of O min ln γ ; γ2 . We assume the existence of an ideal uniform random hash function, and ignore the space required to store it. We later relax this requirement by assuming pseudo- random functions and appealing to a computational variant of differential privacy, SIM-CDP. Our algorithm is built on top of the celebrated Flajolet-Martin (FM) sketch. We show that FM-sketch is differentially private as is, as long as there are p ≈ ln(1/δ)=(εγ) distinct elements in the data set. Along the way, we prove a structural result showing that the maximum of k i.i.d. random variables is statisti- cally close (in the sense of "-differential privacy) to the maximum of (k + 1) i.i.d. -
Secure Multi-Party Computation in Practice
SECURE MULTI-PARTY COMPUTATION IN PRACTICE Marcella Christine Hastings A DISSERTATION in Computer and Information Science Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2021 Supervisor of Dissertation Nadia Heninger Adjunct Associate Professor, University of Pennsylvania Associate Professor, University of California, San Diego Graduate Group Chairperson Mayur Naik Professor and Computer and Information Science Graduate Group Chair Dissertation Committee Brett Hemenway Falk, Research Assistant Professor Stephan A. Zdancewic, Professor Sebastian Angel, Raj and Neera Singh Term Assistant Professor abhi shelat, Associate Professor at Khoury College of Computer Sciences, Northeastern University ACKNOWLEDGMENT This dissertation would have been much less pleasant to produce without the presence of many people in my life. I would like to thank my advisor and my dissertation committee for their helpful advice, direction, and long-distance phone calls over the past six years. I would like to thank my fellow PhD students at the University of Pennsylvania, especially the ever-changing but consistently lovely office mates in the Distributed Systems Laboratory and my cohort. Our shared tea-time, cookies, disappointments, and achievements provided an essential community that brought me great joy during my time at Penn. I would like to thank the mentors and colleagues who hosted me at the Security and Privacy Lab at the University of Washington in 2018, the Software & Application Innovation Lab at Boston University in 2019, and the Cryptography and Privacy Research group at Microsoft Research in 2020. My career and happiness greatly benefited from spending these summers exploring fresh research directions and rediscovering the world outside my own work. -
A Decade of Lattice Cryptography
Full text available at: http://dx.doi.org/10.1561/0400000074 A Decade of Lattice Cryptography Chris Peikert Computer Science and Engineering University of Michigan, United States Boston — Delft Full text available at: http://dx.doi.org/10.1561/0400000074 Foundations and Trends R in Theoretical Computer Science Published, sold and distributed by: now Publishers Inc. PO Box 1024 Hanover, MA 02339 United States Tel. +1-781-985-4510 www.nowpublishers.com [email protected] Outside North America: now Publishers Inc. PO Box 179 2600 AD Delft The Netherlands Tel. +31-6-51115274 The preferred citation for this publication is C. Peikert. A Decade of Lattice Cryptography. Foundations and Trends R in Theoretical Computer Science, vol. 10, no. 4, pp. 283–424, 2014. R This Foundations and Trends issue was typeset in LATEX using a class file designed by Neal Parikh. Printed on acid-free paper. ISBN: 978-1-68083-113-9 c 2016 C. Peikert All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording or otherwise, without prior written permission of the publishers. Photocopying. In the USA: This journal is registered at the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923. Authorization to photocopy items for in- ternal or personal use, or the internal or personal use of specific clients, is granted by now Publishers Inc for users registered with the Copyright Clearance Center (CCC). The ‘services’ for users can be found on the internet at: www.copyright.com For those organizations that have been granted a photocopy license, a separate system of payment has been arranged. -
Hard Communication Channels for Steganography
Hard Communication Channels for Steganography Sebastian Berndt1 and Maciej Liśkiewicz2 1 University of Lübeck, Lübeck, Germany [email protected] 2 University of Lübeck, Lübeck, Germany [email protected] Abstract This paper considers steganography – the concept of hiding the presence of secret messages in legal communications – in the computational setting and its relation to cryptography. Very re- cently the first (non-polynomial time) steganographic protocol has been shown which, for any communication channel, is provably secure, reliable, and has nearly optimal bandwidth. The security is unconditional, i.e. it does not rely on any unproven complexity-theoretic assumption. This disproves the claim that the existence of one-way functions and access to a communication channel oracle are both necessary and sufficient conditions for the existence of secure steganogra- phy in the sense that secure and reliable steganography exists independently of the existence of one-way functions. In this paper, we prove that this equivalence also does not hold in the more realistic setting, where the stegosystem is polynomial time bounded. We prove this by construct- ing (a) a channel for which secure steganography exists if and only if one-way functions exist and (b) another channel such that secure steganography implies that no one-way functions exist. We therefore show that security-preserving reductions between cryptography and steganography need to be treated very carefully. 1998 ACM Subject Classification E.3 Data Encryption Keywords and phrases provable secure steganography, cryptographic assumptions, pseudoran- dom functions, one-way functions, signature schemes Digital Object Identifier 10.4230/LIPIcs.ISAAC.2016.16 1 Introduction Digital steganography has recently received substantial interest in modern computer science since it allows secret communication without revealing its presence. -
Algebraic Pseudorandom Functions with Improved Efficiency from the Augmented Cascade*
Algebraic Pseudorandom Functions with Improved Efficiency from the Augmented Cascade* DAN BONEH† HART MONTGOMERY‡ ANANTH RAGHUNATHAN§ Department of Computer Science, Stanford University fdabo,hartm,[email protected] September 8, 2020 Abstract We construct an algebraic pseudorandom function (PRF) that is more efficient than the classic Naor- Reingold algebraic PRF. Our PRF is the result of adapting the cascade construction, which is the basis of HMAC, to the algebraic settings. To do so we define an augmented cascade and prove it secure when the underlying PRF satisfies a property called parallel security. We then use the augmented cascade to build new algebraic PRFs. The algebraic structure of our PRF leads to an efficient large-domain Verifiable Random Function (VRF) and a large-domain simulatable VRF. 1 Introduction Pseudorandom functions (PRFs), first defined by Goldreich, Goldwasser, and Micali [GGM86], are a fun- damental building block in cryptography and have numerous applications. They are used for encryption, message integrity, signatures, key derivation, user authentication, and many other cryptographic mecha- nisms. Beyond cryptography, PRFs are used to defend against denial of service attacks [Ber96, CW03] and even to prove lower bounds in learning theory. In a nutshell, a PRF is indistinguishable from a truly random function. We give precise definitions in the next section. The fastest PRFs are built from block ciphers like AES and security is based on ad-hoc inter- active assumptions. In 1996, Naor and Reingold [NR97] presented an elegant PRF whose security can be deduced from the hardness of the Decision Diffie-Hellman problem (DDH) defined in the next section. -
Hardness of Non-Interactive Differential Privacy from One-Way
Hardness of Non-Interactive Differential Privacy from One-Way Functions Lucas Kowalczyk* Tal Malkin† Jonathan Ullman‡ Daniel Wichs§ May 30, 2018 Abstract A central challenge in differential privacy is to design computationally efficient non-interactive algorithms that can answer large numbers of statistical queries on a sensitive dataset. That is, we would like to design a differentially private algorithm that takes a dataset D Xn consisting of 2 some small number of elements n from some large data universe X, and efficiently outputs a summary that allows a user to efficiently obtain an answer to any query in some large family Q. Ignoring computational constraints, this problem can be solved even when X and Q are exponentially large and n is just a small polynomial; however, all algorithms with remotely similar guarantees run in exponential time. There have been several results showing that, under the strong assumption of indistinguishability obfuscation (iO), no efficient differentially private algorithm exists when X and Q can be exponentially large. However, there are no strong separations between information-theoretic and computationally efficient differentially private algorithms under any standard complexity assumption. In this work we show that, if one-way functions exist, there is no general purpose differen- tially private algorithm that works when X and Q are exponentially large, and n is an arbitrary polynomial. In fact, we show that this result holds even if X is just subexponentially large (assuming only polynomially-hard one-way functions). This result solves an open problem posed by Vadhan in his recent survey [Vad16]. *Columbia University Department of Computer Science. -
Communication Complexity (For Algorithm Designers)
Full text available at: http://dx.doi.org/10.1561/0400000076 Communication Complexity (for Algorithm Designers) Tim Roughgarden Stanford University, USA [email protected] Boston — Delft Full text available at: http://dx.doi.org/10.1561/0400000076 Foundations and Trends R in Theoretical Computer Science Published, sold and distributed by: now Publishers Inc. PO Box 1024 Hanover, MA 02339 United States Tel. +1-781-985-4510 www.nowpublishers.com [email protected] Outside North America: now Publishers Inc. PO Box 179 2600 AD Delft The Netherlands Tel. +31-6-51115274 The preferred citation for this publication is T. Roughgarden. Communication Complexity (for Algorithm Designers). Foundations and Trends R in Theoretical Computer Science, vol. 11, nos. 3-4, pp. 217–404, 2015. R This Foundations and Trends issue was typeset in LATEX using a class file designed by Neal Parikh. Printed on acid-free paper. ISBN: 978-1-68083-115-3 c 2016 T. Roughgarden All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording or otherwise, without prior written permission of the publishers. Photocopying. In the USA: This journal is registered at the Copyright Clearance Cen- ter, Inc., 222 Rosewood Drive, Danvers, MA 01923. Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by now Publishers Inc for users registered with the Copyright Clearance Center (CCC). The ‘services’ for users can be found on the internet at: www.copyright.com For those organizations that have been granted a photocopy license, a separate system of payment has been arranged. -
Omer Reingold, June 2017
Omer Reingold, June 2017 My research is focused on a wide range of topics within the Foundations of Computer Science. In particular, my core areas, which include my most significant contributions, are Computational Complexity and the Foundations of Cryptography, with an emphasis on Randomness, Derandomization and Explicit Combinatorial Constructions. However, I am interested in a much broader range of topics (some closer and some further away from my core areas). Examples include Differential Privacy and Fairness, Game Theory, Hashing and Data Structures, Resource Allocation and Data Analysis. Current Academic Employment: Professor of Computer Science, Stanford University, Since Feb. 2015. Education: • 1994-1998 Weizmann Institute of Science, Rehovot, Israel. Ph.D. in Computer Science. Thesis title: Pseudo-random synthesizers, functions and permutations. Advisor: Prof. Moni Naor. • 1991-1994 Tel-Aviv University, Tel-Aviv, Israel. B.Sc in Mathematics and Computer Science - Summa Cum Laude. Selected Awards and distinctions (additional awards below): • The 2009 Gödel Prize for outstanding papers in the area of theoretical computer science (jointly with Salil Vadhan and Avi Wigderson). • 2005 ACM Grace Murray Hopper Award. Awarded by the Association for Computing Machinery (ACM) to “the outstanding young computer professional of the year.” • ACM Fellow (2014) Previous Academic Employment and Short Term Visits: • Feb 2015 – September 2016 Principal Research Engineer, Samsung Research America (SRA) • Nov 2014 – Feb 2015 (while on leave from -
An Axiomatic Approach to Block Rewards
An Axiomatic Approach to Block Rewards Xi Chen Christos Papadimitriou Tim Roughgarden [email protected] [email protected] [email protected] Columbia University Columbia University Columbia University New York, NY 10027 New York, NY 10027 New York, NY 10027 ABSTRACT of view and the methodology of Economic Theory, the science of Proof-of-work blockchains reward each miner for one completed incentives. block by an amount that is, in expectation, proportional to the Flaws in the incentives of a blockchain protocol can manifest number of hashes the miner contributed to the mining of the block. themselves at multiple timescales. For longest-chain proof-of-work Is this proportional allocation rule optimal? And in what sense? And blockchains like Bitcoin, the most well-studied incentive-based what other rules are possible? In particular, what are the desirable attacks, such as selfish mining [4, 5, 10] and transaction sniping [3], properties that any łgoodž allocation rule should satisfy? To answer concern miners reasoning strategically over multiple block creation these questions, we embark on an axiomatic theory of incentives in epochs. For example, in selfish mining, a miner relinquishes revenue proof-of-work blockchains at the time scale of a single block. We in the short term to achieve greater revenue (in expectation) in the consider desirable properties of allocation rules including: symme- long run via a type of forking attack. try; budget balance (weak or strong); sybil-proofness; and various This paper studies incentive issues and potential deviations from grades of collusion-proofness. We show that Bitcoin’s proportional intended miner behavior at the most basic time scale, that of a allocation rule is the unique allocation rule satisfying a certain single block creation epoch.