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Hyperledger Sawtooth

Sawtooth is a decentralized platform to build your own permissioned DApps. The main contributer to Sawtooth is Intel. What makes Sawtooth special is that it uses a Trusted Execution Environment (TEE) (it currently supports Intel's SGX only) for consensus, which makes the network very safe and trustworthy and increases trust in the final result of the consensus.

The TEE is a secure area of the main processor. It guarantees that the code and data loaded inside is protected with respect to confidentiality and integrity. The TEE as an isolated execution environment that provides security features such as isolated execution, integrity of Trusted Applications, along with confidentiality of their assets.

Proof of Elapsed Time (PoET) is the name of the consensus protocol that Sawtooth uses. In PoET, there are special types of nodes called as validators. Validators must run their node on an SGX-supported CPU. This is how PoET works.

Every validator requests a wait time from an enclave (a trusted function). The validator with the shortest wait time for a particular transaction block is elected the leader. One function, say CreateTimer, creates a timer for a transaction block that is guaranteed to have been created by the enclave. Another function, say CheckTimer, verifies that the timer was created by the enclave and, if it has expired, creates an attestation that can be used to verify that the validator did, in fact, wait the allotted time before claiming the leadership role. PoET randomly distributes leadership election across the entire population of validators. The probability of election is proportional to the resources contributed (in this case, resources are general-purpose processors with a TEE). An attestation of execution provides information for verifying that the certificate was created within the enclave (and that the validator waited the allotted time). Further, the low cost of participation increases the likelihood that the population of validators will be large, increasing the robustness of the consensus algorithm.

Sawtooth also supports smart contracts (specifically, Ethereum smart contracts can be executed on Sawtooth). Performance-wise, Sawtooth scales well in terms of large numbers of transactions and nodes.