What’s Proof of Elapsed Time

Proof of Elapsed Time is one more consensus mechanisms. Also known as PoET, there’s not much PoETry in this consensus mechanism.

Money is a bubble that never pops. It’s a consensus hallucination.

-Naval Ravikant

Also known as PoET, this consensus is everything but poetry! The algorithm is used mostly in permissioned blockchains like Hyperledger Sawtooth (in addition to PBFT). PoET uses a lottery-style random selection to select the node that is going to win the new block.

PoET started to be used in Hyperledger Sawtooth in 2016/2017, introduced by Intel. The “miners” must first join the network, gaining a membership certificate. Once they are in the network, the nodes need to wait a certain amount of time that is randomly decided. The miner must wait at least the amount of time that was defined before starting mining a new block into the blockchain. In PoET, the miner that has the shortest amount of time is elected to do the block mining that round. The system tends to be fair and choose miners with a good degree of randomness. It doesn’t require much electricity consumption and miners can “go to sleep” while they wait for their turn.

POeT is based on special CPUs developed by Intel called SGX — Software Guard Extensions. SGX allows a logical separation of the CPU memory that cannot be accessed or changed. These parts are also called enclaves and can perform isolated commands and memory encryption. Only enclaves can access and changed stored in this compartment. The code is encrypted and cannot be accessed outside the enclave, making it very secure for the processes that happen inside the enclave.

The main use case for proof of elapsed time is Hyperledger Sawtooth, a permissioned blockchain designed for enterprises that mainly uses POeT as a consensus mechanism. Sawtooth it’s used to develop and make smart contracts, as well as distributed ledgers. It can be deployed on-premise or on the cloud. The consensus mechanisms available for Sawtooth are RAFT, PBFT or POeT, and the interesting thing is that the consensus mechanism can be changed on the fly according to the needs or growth of the network. It is compatible with a wide range of use cases from healthcare…