SoK: TEE-Assisted Confidential Smart Contract

The blockchain-based smart contract lacks privacy, since the state and instruction code are exposed to public. Combining smart-contract execution with Trusted Execution Environments provides an efficient solution, called TEE-assisted contracts (TCSC), for protecting confidentiality of states. However, combination approaches varied, a systematic study is absent. Newly released systems may fail draw upon experience learned from existing protocols, such as repeating known design mistakes or applying TEE technology in insecure ways. In this paper, we first investigate categorize into two types: layer-one solution layer-two solution. Then, establish analysis framework capture their common aspects, covering desired properties (for services), threat models, security considerations underlying systems). Based on our taxonomy, identify ideal functionalities, uncover fundamental flaws challenges each specification’s design. We believe that work would provide guide development contracts, well evaluate future TCSC systems.