Steven Goldfeder will present his FPO, "Off-chain protocols for cryptocurrencies" on Wednesday, 8/29/2018 at 2:00 PM in CS 402.

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 Arvind Narayanan

Everyone is invited to attend. A copy of his thesis is available in CS 310.

The thesis abstract follows below.

The limits of Bitcoin’s scripting language motivate the need for o↵-blockchain protocols

that extend the functionality of Bitcoin scripts. These protocols are run out-ofband

by the transacting parties, but they are constructed in a manner that cryptographically

binds them to on-chain scripts. Even with the advent of Ethereum, which

provides a much richer scripting language, there are still privacy and scalability benefits

to running o↵-chain protocols, even when on-chain analogs exist.

We present o↵-chain protocols for a variety of applications as well as a general

framework for o↵-chain smart contracts. An important tool for constructing o↵-chain

protocols is threshold-signatures, a primitive that enables distributing the signing

power of a given public key into n shares, such that at least k shares are required to

produce a signature from that key. We show how to construct threshold signatures

that are compatible with Bitcoin, and we then use this primitive to build o↵-chain

protocols for privacy-preserving access control and escrow services. Turning to more

advanced smart contracts, we present o↵-chain protocols for the fair-exchange of

digital goods and services for payment. Finally, we present Arbitrum, a private and

scalable smart contract system which enables running arbitrary smart contracts for

which the code is executed o↵-chain and disputes are resolved on-chain.