אירועים והרצאות בפקולטה למדעי המחשב ע"ש הנרי ומרילין טאוב

As decentralized ledgers and blockchains become more common,  cross-chain interoperability becomes essential to making those ledgers useful. In a cross-chain task, $m$ active, Byzantine parties undertake to trade assets using n passive but trustworthy smart contracts. Each party seeks an outcome that maximizes its own utility in the presence of Byzantine counterparties. This talk introduces a novel task called ``cross-chain consensus''.

We show that cross-chain consensus is \emph{universal}, meaning that any cross-chain consensus protocol can be transformed into a protocol for any other well-formed cross-chain task. We show that cross-chain consensus is impossible using unsigned messages, even if communication channels are authenticated. If each party can generate signed messages verifiable on all the blockchains, then there is a tight bound of $\Theta(m)$ communication rounds, where $m$ is the number of participating parties. Moreover, there is a communication-round optimal protocol that uses a finite number of precomputed signed messages.

Joint work with Sucharita Jayanti.