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.