Blockchain & Cryptocurrency Glossary

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Proof-of-Elapsed-Time

1 min read
Pronunciation
[proof uhv ih-lapst tahym]
Analogy
Imagine a group of people wanting to take turns performing a task. Each person gets a sealed envelope from a trusted, tamper-proof timer machine (the TEE). The envelope tells them how long they have to wait. Everyone opens their envelope simultaneously, and the person with the shortest wait time gets to perform the task (create a block). The TEE ensures the wait times are random and fair, and that no one can cheat by knowing the wait times in advance or faking their wait.
Definition
A consensus mechanism, primarily developed by Intel, that uses a trusted execution environment (TEE) like Intel SGX to ensure a fair lottery system for determining who gets to create the next block. Each validator requests a wait time from the TEE, and the one with the shortest wait time wins.
Key Points Intro
PoET uses trusted hardware to achieve Nakamoto-style consensus with low energy consumption.
Key Points

Relies on a Trusted Execution Environment (TEE), such as Intel SGX, to generate random wait times.

Validators run a special piece of code inside the TEE.

The validator whose TEE-assigned timer expires first gets to create the next block.

Designed to be energy-efficient, similar to PoS, but with a different mechanism for leader selection.

Primarily used in permissioned blockchain networks like Hyperledger Sawtooth.

Example
Hyperledger Sawtooth can be configured to use PoET for its consensus, allowing nodes with Intel SGX capabilities to participate in a lottery-like leader election process without high CPU usage.
Technical Deep Dive
In PoET, each validator node uses its TEE to request a random wait duration. The TEE ensures that this duration is generated fairly and that the validator cannot tamper with it. The validator then 'sleeps' for this duration. The first validator whose timer expires broadcasts a certificate (attestation) from its TEE proving it waited the assigned time, along with the new block. Other nodes can verify this TEE attestation. This process mimics the random chance of finding a block in PoW but without the intensive computation.
Security Warning
PoET's security relies heavily on the integrity and security of the Trusted Execution Environment (TEE) provided by the hardware manufacturer (e.g., Intel SGX). If the TEE itself has vulnerabilities or can be compromised, the fairness and security of the consensus mechanism can be broken. It also introduces a dependency on specific hardware.
Related Terms
PoET
Consensus
Intel SGX
Hyperledger Sawtooth
Permissioned Blockchain

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