SuSy: a blockchain-agnostic cross-chain asset transfer gateway protocol based on Gravity

This document is a specialized technical description of one of the potential implementations of a second layer protocol over Gravity, a blockchain-/token-agnostic decentralized oracle protocol. The SuSy protocol prescribes an implementation of cross-chain transfers of digital assets (tokens) in blockchain networks that support smart contracts, focused primarily on popular blockchains with varying architectures, consensuses and cryptography. SuSy is centered exclusively around technical implementation of transfers, without bringing any incentive models for cross-chain transfer providers. In addition, we describe the most popular inter-chain communication solutions such as Polkadot, Cosmos Hub, Rainbow and RenVM, as a backdrop for the new solution proposed in this paper.