  Decentralized Finance (DeFi), in which digital assets are exchanged without
trusted intermediaries, has grown rapidly in value in recent years. The global
DeFi ecosystem is fragmented into multiple blockchains, fueling the demand for
cross-chain commerce. Existing approaches for cross-chain transactions, e.g.,
bridges and cross-chain deals, achieve atomicity by locking assets in escrow.
However, locking up assets increases the financial risks for the participants,
especially due to price fluctuations and the long latency of cross-chain
transactions. Stablecoins, which are pegged to a non-volatile asset such as the
US dollar, help mitigate the risk associated with price fluctuations. However,
existing stablecoin designs are tied to individual blockchain platforms, and
trusted parties or complex protocols are needed to exchange stablecoin tokens
between blockchains.
  Our goal is to design a practical stablecoin for cross-chain commerce.
Realizing this goal requires addressing two challenges. The first challenge is
to support a large and growing number of blockchains efficiently. The second
challenge is to be resilient to price fluctuations and blockchain platform
failures. We present CroCoDai to address these challenges. We also present
three prototype implementations of our stablecoin system, and show that it
incurs small execution overhead.
