[Busec] Fwd: [Toc-visitors] [Toc] TALK: Thesis Defense, Sergey Gorbunov: Cryptographic Tools for the Cloud

Leonid Reyzin reyzin at cs.bu.edu
Mon May 11 10:45:17 EDT 2015

---------- Forwarded message ----------
From: Debbie Lehto <dlehto at csail.mit.edu>
Date: Tue, May 5, 2015 at 8:58 AM
Subject: [Toc-visitors] [Toc] TALK: Thesis Defense, Sergey Gorbunov:
Cryptographic Tools for the Cloud
To: toc at csail.mit.edu

 Thesis Defense, Sergey Gorbunov: Cryptographic Tools for the Cloud

 *Speaker:* Sergey Gorbunov

*Date:* Tuesday, May 12, 2015

*Time:* 10:15 AM to 11:30 AM

*Refreshments:* 10:00 AM

*Location:* G449 Patil/Kiva

*Host:* Shafi Goldwasser, Ronald Rivest and Vinod Vaikuntanathan


Classical cryptography is playing a major role in securing the Internet.
Banking transactions, medical records, personal and military messages are
transmitted securely through the Internet using classical encryption and
signature algorithms designed and developed over the last decades. However,
today we face new security challenges that arise in cloud settings that
cannot be solved by these classical algorithms. In this thesis, we address
three major challenges that arise in cloud settings and present new
cryptographic algorithms to solve them.

Privacy of data. How can a user efficiently and securely share data with
multiple authorized receivers through the cloud?
To address this challenge, we present attribute-based and predicate
encryption schemes for circuits of any arbitrary polynomial size. Our
constructions are secure under the standard learning with errors (LWE)
assumption. Previous constructions were limited to Boolean formulas,
captured by the complexity class NC1.

Privacy of programs. How can a user share a program, which may include some
secrets, preserving its functionality and without leaking any information
about the secrets? Program obfuscation is a mechanism that allows to
scramble a program preserving its input/output functionality while
preventing reverse engineering. We describe a new graph-induced multilinear
maps from lattices and show how it can be used to construct a candidate
general purpose program obfuscator. Our construction uses standard (random)
integer lattices. Previous constructions of multilinear maps relied on
hardness of problems in either principal ideal lattices or integers and
were subjected to many algebraic attacks.

Integrity of computations. How can a user outsource computations over a
large database to the cloud and allow anyone efficiently authenticate the
results? To address this, we present a fully homomorphic signature scheme
for arbitrary circuits. The scheme allows the cloud server to run arbitrary
computation, represented by circuit C, on the signed data x to get y=C(x)
and produce a short ``proof'' P that can be used by anyone to authenticate
the output y. Our scheme is secure under the short integer solution (SIS)
problem in standard lattices. Previous constructions of homomorphic
signatures were limited to evaluating polynomials of constant degree.

Committee: Shafi Goldwasser, Ronald Rivest and Vinod Vaikuntanathan

Deborah Lehto
Assistant to Profs. S Aaronson, S Goldwasser, D Moshkovitz, R Rivest,
and M Sudan
Computer Science and Artifical Intelligence Laboratory
Phone 617.324.7303

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