Time+Place: Tuesday 24/03/2015 14:30 Room 337-8 Taub Bld.
Title: Zerocash: Decentralized Anonymous Payments from Bitcoin
Speaker: Eli Ben-Sasson - Colloquium Lecture http://www.cs.technion.ac.il/people/eli/
Affiliation: Computer Science, Technion


Bitcoin is the first digital currency to see widespread adoption. While
payments are conducted between pseudonyms, Bitcoin cannot offer strong
privacy guarantees: payment transactions are recorded in a public
decentralized ledger, from which much information can be deduced. 
Zerocoin (Miers et al., IEEE S&P 2013) tackles some of these privacy issues 
by unlinking transactions from the payment's origin. Yet, it still reveals
payments' destinations and amounts, and is limited in functionality.

In this paper, we construct a full-fledged ledger-based digital currency
with strong privacy guarantees. Our results leverage recent advances in
zero-knowledge Succinct Non-interactive ARguments of Knowledge 

First, we formulate and construct decentralized anonymous payment 
schemes (DAP schemes). A DAP scheme enables users to directly pay each other
privately: the corresponding transaction hides the payment's origin,
destination, and transferred amount. We provide formal definitions and
proofs of the construction's security.

Second, we build Zerocash, a practical instantiation of our DAP scheme
construction. In Zerocash, transactions are less than 1 kB and take 
under 6 ms to verify --- orders of magnitude more efficient than the 
less-anonymous Zerocoin and competitive with plain Bitcoin.

Joint work with Alessandro Chiesa, Christina Garman, Matthew Green, Ian
Miers, Eran Tromer, and Madars Virza.

Short Bio:

Eli Ben-Sasson received his PhD at Hebrew University under the
supervision of Avi Wigderson. Since 2005 he has been a faculty
member of Technion - Israel Institute of Technology. His area of
interest is theoretical computer science with an emphasis on the
interplay between proofs and computation.

Desserts will be served from 14:15
Lecture starts at 14:30