The adoption of decentralized, tamper-proof ledger systems is paving the way for new applications and opportunities in different contexts. While most research aims to improve their scalability, privacy, and governance issues, interoperability has received less attention. Executing transactions across various blockchains is notably instrumental in unlocking the potential of novel applications, particularly in the financial sector, where their potential would otherwise be significantly diminished. Therefore, interoperable ledgers are crucial to ensure the expansion and further adoption of such a technology in various contexts. In this paper, we present a protocol that uses a combination of trusted execution environment (TEE) and blockchains to enable interoperability over independent semi-centralized CBDC ledgers, guaranteeing the atomicity of inter-bank transfers. Our interoperability protocol uses a custom adaptation of atomic swap protocol and is executed by any pair of CBDC instances to realize a one-way transfer. It ensures features such as atomicity, verifiability, correctness, censorship resistance, and privacy while offering high scalability in terms of the number of CBDC instances. Our approach enables to possible deployment scenarios that can be combined: (1) CBDC instances represent central banks of multiple countries, and (2) CBDC instances represent the set of retail banks and a paramount central bank of a single country. We provide a detailed description of our protocol as well as an extensive analysis of its benefits, features, and security. In this WIP paper, we made a proof-of-concept implementation and made a partial evaluation, while the more extensive evaluation will be made in our future work.

翻译：去中心化、防篡改账本系统的采用正在为不同领域的应用和机遇开辟新道路。尽管大多数研究致力于提升系统可扩展性、隐私保护及治理问题，但互操作性受到的关注相对较少。跨区块链执行交易在释放新型应用潜力方面具有显著价值，尤其在金融领域——若缺乏互操作性，其潜在价值将大幅受限。因此，可互操作的账本系统对于确保该技术在各类场景中的扩展与推广至关重要。本文提出一种结合可信执行环境（TEE）与区块链的协议，实现独立半中心化央行数字货币账本间的互操作性，并保障银行间转账的原子性。该互操作协议采用原子交换协议的自定义适配版本，由任意两个央行数字货币实例执行以实现单向转账，在保持高可扩展性（支持大量央行数字货币实例）的同时，具备原子性、可验证性、正确性、抗审查性及隐私保护等特性。我们的方法支持两种可组合部署场景：（1）央行数字货币实例代表多国央行；（2）央行数字货币实例代表单一国家内的零售银行集合与主导央行。本文提供了协议的详细描述，并对其优势、特性及安全性进行了全面分析。作为研究进展中（WIP）论文，我们完成了概念验证实现并进行了部分评估，更全面的评估将在未来工作中展开。