Non-Malleable Codes for Bounded Depth, Bounded Fan-in Circuits
Non-malleable codes are a relaxation of error correcting codes, for settings in which privacy, but not necessarily correctness, is desired. Instead of requiring that after modification—i.e. tampering—of the codeword, the original message can always be recovered, non-malleable codes allow a different message to be recovered, as long as the recovered message is unrelated to the original message. This relaxation potentially allows for the construction of coding schemes for rich classes of tampering classes, beyond what can be done for error correcting codes. In applications, non-malleable codes are used to encode the memory of a device, and thus protect against (certain classes) of adversarial tampering.
Lower-Bounds on Assumptions behind Indistinguishability Obfuscation
In this talk, we first show that basing IO on a variety of assumptions (e.g., trapdoor permutations, bi-linear maps, etc) in a weakly black-box way is as hard as basing public-key encryption on one-way functions (in a non-black-box way). The latter has remained as one of the most challenging open questions in cryptography. Then, by combining our results with a recent result of Brakerski, Brzuska, and Fleischhacker, we rule out any fully black-box construction of IO from the same set of primitives assuming the existence of one-way functions and that the polynomial-hierarchy does not collapse.
New Inference Attacks on Order-Preserving and Order-Revealing Encryption
Accessing Data while Preserving Privacy
We present a new model of differentially private storage where differential privacy is preserved even against an attacker that controls the data and the queries made to it. We give a generic construction of differentially private storage that combines ORAM and differentially private sanitizers. We also provide efficient constructions and lower bounds for some specific query sets. We have implemented some of our algorithms, and report on their efficiency.Joint work with Georgios Kellaris, George Kollios, Kobbi Nissim, and Adam O’Neill.
Bio: Georgios is currently a Post-Doctoral Fellow at CRCS, Harvard University, and at Boston University. He received his Ph.D. degree in Computer Science and Engineering from the Hong Kong University of Science and Technology (2015), under the supervision of prof. Dimitris Papadias, and with the support of the Hong Kong Ph.D. Fellowship Scheme. He holds a 4-year B.Sc. in Informatics and Telecommunications from the University of Athens (2006) and a 2-year M.Sc. degree in Digital Systems from the University of Piraeus (2008). He has worked as a researcher at the University of Piraeus in Greece, the Singapore Management University and the Nanyang Technological University in Singapore, and at Boston University. His research interests include databases and differential privacy.
DC CRYPTO DAY
FRIDAY, OCTOBER 30
JOHNS HOPKINS UNIVERSITY (HOMEWOOD CAMPUS) ∙ BALTIMORE, MD
Be sure to join us for the next DC area Crypto Day scheduled from 10:00 a.m. – 5:00 p.m. on Friday, October 30 at the Homewood Campus of Johns Hopkins University. The theme of this installment is Bitcoin.
Parking Location: South Garage
3100 Wyman Park Drive
Baltimore, MD 21211
Location of Talks: Sherwood Room, Levering Hall
– Google Maps Link
– Campus map.
*Please note that Levering Hall is building number 40 on the map and South Garage Parking is the one next to building 45 on the map.
10:00 AM – 11:00 AM |David Evans, University of Virginia
11:10 AM – 12:10 PM |Andrew Miller, University of Maryland
12:10 PM – 1:40 PM | Lunch
1:40 PM – 2:40 PM |Ranjit Kumaresan, Massachusetts Institute of Technology
2:50 PM – 3:50 PM |Matthew Green, Johns Hopkins University
4:00 PM – 5:00 PM | Panel discussion
Note that there is a 10:00 minute break between the talks.
Please find the titles and abstracts below.
Speaker: David Evans, University of Virginia
Title: Trick or Treat?: Bitcoin for Non-Believers, Cryptocurrencies for Cypherpunks
Abstract: This (non-research) talk will start with a tutorial introduction to cryptocurrencies and how bitcoin works (and doesn’t work) today. We’ll touch on some of the legal, policy, and business aspects of bitcoin and discuss some potential research opportunities in cryptocurrencies.
Speaker: Andrew Miller, University of Maryland
Title: Privacy-preserving Smart Contracts
Abstract: Existing blockchain-based cryptocurrencies such as Bitcoin and Ethereum, store all financial transactions in the clear on the blockchain. This compromises the privacy of financial transactions, which is essential in numerous applications.
Hawk is a blockchain-based smart contract system that stores encrypted transactions on the blockchain, and relies on cryptography to retain the security of the cryptocurrency. A Hawk programmer can write a private smart contract in an intuitive manner without having to implement cryptography, and our compiler automatically generates an efficient cryptographic protocol where contractual parties interact with the blockchain, using cryptographic primitives such as succinct zero-knowledge proofs.
To formally define and reason about the security of our protocols, we also formalize a new simulation-based “blockchain model” of secure computation, which is of independent interest.
Speaker: Ranjit Kumaresan, Massachusetts Institute of Technology
Title: How to Use Bitcoin to Design Fair Protocols
Abstract: I will talk about a recent line of work that integrates traditional secure computation with a formal financial framework. This line of work identifies and abstracts some key transaction functionalities offered by the Bitcoin network, and shows how to incentivize correct behavior in secure computation (and other cryptographic tasks) in a model where parties have access to such a transaction functionality.
Speaker: Matt Green, Johns Hopkins University
*Please note that lunch will not be provided, click on Crypto Conference Dining Options to check out local nearby options.
Please RSVP to Sr. Academic Program Coordinator Jessica Finkelstein at firstname.lastname@example.org by Friday, October 23.
This DC Crypto Day is hosted by:
p.s. The first DC area crypto day was held at the University of Maryland at College Park. See here for the program and more information.