<html><body><div id="zimbraEditorContainer" style="font-family: garamond,new york,times,serif; font-size: 12pt; color: #000000" class="17"><div></div><div data-marker="__QUOTED_TEXT__"><p style="margin-left: 50px;" data-mce-style="margin-left: 50px;">Steven Goldfeder will present his FPO, "Off-chain protocols for cryptocurrencies" on Wednesday, 8/29/2018 at 2:00 PM in CS 402.<br></p><p style="margin-left: 50px;" data-mce-style="margin-left: 50px;">The members of his committee are as follows: Adviser: Arvind Narayanan; Readers: Edward Felten and Rosario Gennaro (City College - CUNY); Examiners: Matt Weinberg, Mark Zhandry, and <span style="color: #000000; font-family: garamond, 'new york', times, serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: garamond, 'new york', times, serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">Arvind Narayanan</span><!--EndFragment--></p><p style="margin-left: 50px;" data-mce-style="margin-left: 50px;"><span style="color: #000000; font-family: garamond, 'new york', times, serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: garamond, 'new york', times, serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">Everyone is invited to attend. A copy of his thesis is available in CS 310.</span></p><p style="margin-left: 50px;" data-mce-style="margin-left: 50px;"><span style="color: #000000; font-family: garamond, 'new york', times, serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: garamond, 'new york', times, serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">The thesis abstract follows below.</span></p><div style="clear: both;" data-mce-style="clear: both;"><br></div><div>The limits of Bitcoin’s scripting language motivate the need for o↵-blockchain protocols</div><div>that extend the functionality of Bitcoin scripts. These protocols are run out-ofband</div><div>by the transacting parties, but they are constructed in a manner that cryptographically</div><div>binds them to on-chain scripts. Even with the advent of Ethereum, which</div><div>provides a much richer scripting language, there are still privacy and scalability benefits</div><div>to running o↵-chain protocols, even when on-chain analogs exist.</div><div>We present o↵-chain protocols for a variety of applications as well as a general</div><div>framework for o↵-chain smart contracts. An important tool for constructing o↵-chain</div><div>protocols is threshold-signatures, a primitive that enables distributing the signing</div><div>power of a given public key into n shares, such that at least k shares are required to</div><div>produce a signature from that key. We show how to construct threshold signatures</div><div>that are compatible with Bitcoin, and we then use this primitive to build o↵-chain</div><div>protocols for privacy-preserving access control and escrow services. Turning to more</div><div>advanced smart contracts, we present o↵-chain protocols for the fair-exchange of</div><div>digital goods and services for payment. Finally, we present Arbitrum, a private and</div><div>scalable smart contract system which enables running arbitrary smart contracts for</div><div>which the code is executed o↵-chain and disputes are resolved on-chain.</div><p style="margin-left: 50px;" data-mce-style="margin-left: 50px;"><!--EndFragment--></p><br></div></div></body></html>