[Busec] Crypto Reading Group, Tomorrow

Huijia Lin huijial at gmail.com
Mon Apr 22 14:54:46 EDT 2013

Hi All,

Please note that the crypto reading group tomorrow has been moved to 10:00
to 11:30am in the morning and at 32-G882. The talk is by Nir Bitansky and
is also a CIS seminar.

Speaker: Nir Bitansky
Speaker Affiliation: Tel Aviv University
Host: Shafi Goldwasser
Host Affiliation: MIT CSAIL

Date: 4-23-2013
Time: 10:00 AM - 11:30 AM
Location: 32-G882 (Hewlett)


On Thu, Apr 18, 2013 at 4:25 PM, Huijia Lin <huijial at gmail.com> wrote:

> Sorry for the wrong subject of the last email. Note that the next crypto
> reading group is on *next Tuesday*.
> Rachel
> On Thu, Apr 18, 2013 at 4:23 PM, Huijia Lin <huijial at gmail.com> wrote:
>> Dear all:
>> Next Tuesday, Nir Bitansky, from Tel Aviv University will tell us about "On
>> the Impossibility of Approximate Obfuscation and Applications to
>> Resettable Cryptography" (abstract below and full paper at *
>> https://eprint.iacr.org/2012/729*). Please come and enjoy. Breakfast
>> will be provided.
>> Speaker: Nir Bitansky
>> Venue: MIT, 32-D463 (Star)
>> Time: Apr. 23rd, 9:00am --11:00am
>> See you and have a nice day!
>> Rachel
>> ==============================================
>> On the Impossibility of Approximate Obfuscation
>> and Applications to Resettable Cryptography
>> -----------------------------------------------------------------
>> The traditional notion of program obfuscation requires that an
>> obfuscation P' of a program P computes the exact same function as P, but
>> beyond that, the code of P' should not leak any information about P. This
>> strong notion of virtual black-box security was shown by Barak et al.
>> (CRYPTO 2001) to be impossible to achieve, for certain unobfuscatable
>> function families. The same work raised the question of approximate
>> obfuscation, where the obfuscated P' is only required to approximate P;
>> that is, P' only agrees with P with high enough probability on some input
>> distribution.
>> We show that, assuming trapdoor permutations, there exist families of
>> robust unobfuscatable functions for which even approximate obfuscation is
>> impossible. Specifically, obfuscation is impossible even if the obfuscated
>> P' is only required to agree with P with probability slightly more than
>> 1/2, on a uniformly sampled input (below 1/2-agreement, the function
>> obfuscated by P, is not uniquely defined). Additionally, assuming only
>> one-way functions, we rule out approximate obfuscation where P' may output
>> \bot with probability close to 1 but otherwise must agree with P.
>> We demonstrate the power of robust unobfuscatable functions by exhibiting
>> new implications to resettable protocols. Concretely, we reduce the
>> assumptions required for resettably-sound zero-knowledge to one-way
>> functions, as well as reduce round-complexity. We also present a new
>> simplified construction of a simultaneously-resettable zero-knowledge
>> protocol, based on one-way functions, and any simultaneously-resettable
>> witness-indistinguishable protocol. Finally, we construct a three-message
>> simultaneously-resettable witness-indistinguishable argument of knowledge
>> (with a non-black-box knowledge extractor). Our constructions use a new
>> non-black-box simulation technique that is based on a special kind of
>> “resettable slots”. These slots are useful for a non-black-box simulator,
>> but not for a resetting prover.
>> Joint work with Omer Paneth.
>> ================================================
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