Decentralized finance (DeFi) is now a massive aggregator of many financial blockchain protocols. The overall value locked in them is currently valued at around 80 billion USD. Every day, a growing number of new users bring their investments to DeFi. Decentralized finance entails the creation of a single ecosystem of many blockchains that interact with one another. To enable DeFi, the problem of combining and interacting blockchains becomes critical. In this paper we describe the concept of a DeFi protocol, which employs cross-blockchain interface technologies, and show how a prototype pre-sale application based on the proposed concept can be created.