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Proof of Elapsed Time( PoET) in Blockchain

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Proof of Elapsed Time (PoET) is a network consensus algorithm that prevents high resource utilization and energy consumption. It implements a fair lottery system to keep the process more efficient. 

What is Proof of Elapsed Time( PoET)?

Blockchain technology is a distributed ledger used to record any transactions that happen over the network and since Bitcoin’s inception and the introduction of the Proof of Work (PoW) consensus model as the mechanism for a blockchain network’s legitimacy. After numerous other consensus mechanisms have been experimented with and introduced, the Proof of Elapsed Time (PoET) concept is one such mechanism which was invented in early 2016 by Intel Corporation and is one of the fairest blockchain consensus algorithms that enables permissioned blockchain networks to determine who creates the next block. 

Intel in collaboration with other organizations such as the Linux Project and IBM sponsored the Hyperledger Sawtooth project, this open-source project uses the PoET consensus mechanism. Hyperledger Sawtooth is a distributed ledger that is both scalable and adaptable for many uses at the enterprise like supply chain and logistics. This mechanism is based on Byzantine Fault Tolerance and aims to reduce the energy consumption associated with proof of work’s mining process.

  • This algorithm assigns an amount of time to each node in the network randomly. 
  • The node must sleep or do another task for that random wait time.
  • The node that gets the shortest waiting time wakes up and adds its block to the network. 
  • The newly updated information floods among the network participants.

3 Factors Need to Be in Favor for PoEt to Work:

  1. Ensure that the node gets the random waiting time instead.
  2. Check if the nodes are not choosing the shortest wait time on purpose.
  3. Verify if a node has completed the given waiting time or not.

Proof of Elapsed Time

How Does PoET Work?

The PoET mechanism replaces the need for mining intensive rights required in Proof of Work with a randomized timer system. The PoET consensus mechanism distributes the chances of winning across the largest possible number of network participants and every node is likely to be selected by a fair lottery system. 

  • Every node in the blockchain network will generate a random wait time and then sleeps for that specified duration. 
  • Now the first one to wake up, that is, the first node in the network to have its timer expire after completing its specified waiting time wins the block round and it now becomes the block leader which produces the new block and signs the new block with its private key address before adding it to the blockchain network. 
  • After this necessary information is broadcasted to the whole peer network and the same process then repeats for the discovery of the next block.

In this consensus mechanism the problem is ” how to determine the leader of a round of consensus” and whoever solves the computationally intensive cryptographic puzzle of each block round is selected as the leader for the round. For the node to participate in consensus, it downloads the trusted code which requires code attestation by Intel Software Guard Extension (SGX). SGX functions as a Trusted Execution Environment (TEE), which allows selecting, trusted code to run independently of the application that it runs in.

The PoET consensus mechanism is divided into 2 phases:

1. Selection Process: This process involves the following activities:

  • Every node in the network will share its certificate by Intel Software Guard Extension (SGX) which ensures the validity of the node to generate a new block in the network. After this, the node is eligible to get a timer object.
  • The numbers are assigned to each node as a timer object by Intel’s RAND i.e. random number generator. RAND generates difficult-to-detect random numbers. 
  • The time object given to each participating node activates.

2. Generation Process: This process involves the following activities:

  • After the timer object expires, and the node wakes up then the node is eligible to forge a new block to the network.
  • The active node generates the hash of its block of transactions and submits it for acceptance.
  • The update gets flooded to the network.

Therefore, this ends the iteration of mining a new block in a permissioned blockchain network using the PoET consensus algorithm.

PoET Generation Process

Proof of Elapsed Time( PoET) vs Proof of Work (PoW):

Unlike the proof of work (PoW) algorithm, Proof of Elapsed Time( PoET) requires less power consumption, also it allows a node to sleep and switch to other tasks for the specified time, thereby increasing the network’s efficiency in terms of power and time. The PoW mechanism provides a competitive work environment, whereas the PoET mechanism provides a random selection environment.

The below table summarizes the difference between PoET and PoW:

Blockchain typePermissionedPermissionless
Transaction rateMediumLow
Token neededNoYes
Energy efficiencyMore energy efficient.Less energy efficient.
Power ConsumptionLess power consumption.More power consumption.
Network EfficiencyIncreased network efficiency.Less efficient network.
EnvironmentIt provides a random selection environment.It provides a competitive work environment.

Benefits of PoET:

  • Less power consumption: PoET doesn’t require much electricity consumption, and the nodes can “go to sleep” and switch to other tasks for the specified time thereby making the network time and energy efficient.
  • Less resource intensive: PoET also provides a great solution to the “Random Leader Selection Problem” without being resource-intensive or requiring complex mechanisms. It is easily scalable as it allows the network to reach consensus more quickly thus allowing faster processing of transactions. 
  • High transaction rate: PoET can go up to a million transactions per second.
  • Equal opportunity: PoET allows for the same opportunity for the network participants with time object and activation.
  • Permissioned: Since it is a permissioned blockchain network, the process of selecting validators ensures network security against cyberattacks.

Limitations of PoET:

  • Specialized hardware required: Even though it’s cheap there is a requirement for specialized hardware for incorporating the Proof of Elapsed Time consensus algorithm as a result, it cannot be used by most people.
  • Compatibility issues: PoET highly depends on tools by Intel technology which might raise compatibility issues with the other tools. 


PoET is highly efficient and works with SGX which is an emerging technology and future developments surrounding SGX will have a major impact on PoET as a sustainable consensus model. PoET represents another breakthrough in providing Byzantine Fault Tolerance consensus mechanisms for distributed ledger systems.

Last Updated : 09 Jan, 2024
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