International Association
for Cryptologic Research

Privacy-oriented cryptocurrencies like Zerocash only support direct payments and not the execution of more complex contracts. Bitcoin and Ethereum, on the other hand, cannot guarantee privacy, and using them for contract execution leaves open questions about fungibility of the proceeds and requires contract designers to take frontrunning countermeasures. This work reconciles the two worlds and develops a practical framework for decentralized execution of complex contracts that (1) is undetectable to the network at large, (2) maintains anonymity of the potentially mutually distrustful counterparties, (3) guarantees fair termination, and (4) is immediately resistant to frontrunning and miner bribery attacks. This is achieved by leveraging the confidentiality and anonymity guarantees of Zerocash and the verifiability and flexibility of trusted execution environments.