Blockchain
Building in the Right Category - Separating Computation from Consensus
Category of Confidential Blockchain: Systems PDOs, Phala, Ekiden, Oasis and COMMITEE introduce an expendable and interchangeable solution. TEEs are stateless: any particular TEE can be easily replaced once it has crashed or finished its task.
Phala, Ekiden, Oasis can be treated as achieving higher performance blockchain’s in addition to privacy.
Unfortunately, these solutions come with new problems which need to be addressed:
Trusted hardware in general cannot ensure availability. In the case of SGX, a malicious host can terminate enclaves, and even an honest host could lose enclaves in a power cycle. A TEE-blockchain system must tolerate such host failures, ensuring that crashed TEEs can at most delay execution.
Detecting a compromised TEE is still difficult. Given the same input parameters to different TEEs, TEEs are believed to work securely only if their outcomes match. The number of outcomes which need to match balances the integrity of the execution against the speed in which its outputs can be given to consensus validators.
Consensus validators are provided a proof demonstrating the execution results came from a TEE and then commit state changes to blockchain storage.
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