Proof of Elapsed Time

Proof of Elapsed Time (PoET) is a competitive consensus algorithm for blockchain, it can be used in permissioned (private) blockchain networks.

The validation software run in the Trusted Execution Environment (TEE) that is available on some CPU-types. PoET is using SGX which limits the processors to use to Intel.

Nodes in the network running the code in TEE creates evidence it is allowed to validate. Validator nodes receive a timer object and the one expiring first is allowed to create the next block. The amount of CPU capacity reserved affects the timer you get (more CPU => shorter timer). The protocol however does assure randomness in the timers so all nodes can be selected for validation.

A nice explanation can be found on bockonomi.com.

It is very efficient compared to Proof of Work algorithms, downside is it relies on the Intel SGX technology making the protocol dependent on that company.