With the rise of digital currency systems that rely on blockchain to ensure ledger security, the ability to perform cross-chain transactions is becoming a crucial interoperability requirement. Such transactions allow not only funds to be transferred from one blockchain to another (as done in atomic swaps), but also a blockchain to verify the inclusion of any event on another blockchain. Cross-chain bridges are protocols that allow on-chain exchange of cryptocurrencies, on-chain transfer of assets to sidechains, and cross-shard verification of events in sharded blockchains, many of which rely on Byzantine fault tolerance (BFT) for scalability. Unfortunately, existing bridge protocols that can transfer funds from a BFT blockchain incur significant computation overhead on the destination blockchain, resulting in a high gas cost for smart contract verification of events. In this paper, we propose Horizon, a gas-efficient, cross-chain bridge protocol to transfer assets from a BFT blockchain to another blockchain (e.g., Ethereum) that supports basic smart contract execution.

翻译：随着依赖链链以确保分类账安全的数字货币系统的兴起,跨链交易的能力正在成为关键的互操作性要求。 此类交易不仅允许资金从一个链条转移到另一个链条(如原子互换),而且允许将任何事件包括在另一个链条上。 跨链桥是允许在链条上交换密码的规程,允许将资产从链条转移到侧链,以及对碎条中的事件进行跨链核查,其中许多都依靠拜占庭断层容忍度(BFT)进行扩缩。 不幸的是,从一个链条中转移资金的现有桥梁协议在目的地链条上造成了巨大的计算间接费用,导致智能合同事件核查的高气体成本。 在本文中,我们建议“地平线 ”, 一种高效的、跨链桥协议,将资产从一个链条转移到另一个链条(如EFEinum),支持基本的智能合同执行。