What is proof-of-elapsed-time (PoET)?

Proof-of-elapsed-time is one of many consensus mechanisms that are currently used within the blockchain industry. Developed by chip-maker Intel, it is similar to the proof-of-work (PoW) system used by Bitcoin and many others, but it consumes significantly less power by employing a fair lottery system that determines which nodes will validate new blocks.

In this AAG Academy guide, we’ll explain proof-of-elapsed-time (PoET) and how it works in more detail, look at how PoET compares to PoW, and cover its various advantages and disadvantages. We’ll also answer some common questions surrounding the PoET algorithm.

A consensus algorithm is used by blockchain networks to ensure that all transactions are valid and genuine, and that all data is accurate. It is a highly critical element of today’s blockchain industry, so a number of different consensus algorithms have been developed over the years in an effort to improve upon earlier systems and provide different approaches.

PoET, which was first created in 2016, is one of those. It builds upon the foundations laid by PoW, the industry’s original consensus mechanism, but uses a different selection process for validation that eliminates “random leader election.” This drastically reduces the amount of processing power and energy that is required to verify and confirm transactions.

Today, PoET is primarily used by Hyperledger Sawtooth, a distributed ledger that is designed primarily for enterprise users for things like supply chains, logistics, and inventory management. As things stand, there is no cryptocurrency that uses PoET, but that could change in the future.

How does proof-of-elapsed-time (PoET) work?

A blockchain’s consensus algorithm lays out how validators will be chosen to mine or process new blocks. Some consensus mechanisms, like PoW, allow miners to gain an advantage over their competitors by bringing more power. Others, like PoS, allow validators to stake more of their cryptocurrency tokens for a greater chance of being selected. PoET is different.

As its name suggests, PoET uses a randomly generated elapsed time to decide which miner will process the next block, regardless of their processing power. This means that every node on the network has the same chances of “winning” that right and is equally likely to be chosen. Each one waits for a certain period of time, and the first to complete that waiting time wins.

The wait period is randomly predetermined, and each node has a timer that is kept up to date by the PoET algorithm itself. A node can only be assigned a timer once it has been confirmed that they are running trusted code in a secure environment, which eliminates the possibility of bad actors corrupting the system by altering that code. All results are verifiable by other participants.

The chosen node then processes a new block in much the same way a miner would in the PoW system; the block is assigned a hash based on its fill of transactions, and it is submitted for approval by the rest of the network. Finally, it is added to the rest of the chain, and the PoET process is repeated to select a miner for the next block.

Proof-of-elapsed-time vs. proof-of-work (PoW)

We have an in-depth guide to proof-of-work for those who want to learn about it in detail, but the fundamental difference between PoW and PoET, as we touched on above, is the way in which miners are selected. PoW has no fair lottery system like PoET. Instead, miners must compete against each other to solve complex cryptographic puzzles as quickly as possible.

These puzzles require incredibly powerful systems with specialized hardware, which is why Bitcoin miners are constantly pushing for the latest technologies, or building dedicated crypto mining farms, in an effort to gain an advantage over others. Those who solve puzzles first are awarded the opportunity to process a new block, for which they receive new coins for their work.

This means that mining nodes in a PoW network must be active at all times — constantly working away to solve puzzles as quickly as possible. Whereas, in PoET, nodes go to sleep and don’t wake up until their wait time is over and it is their turn to process a new block. This means that they consume very little energy when they are not actively working.

That doesn’t mean, however, that you can use any old computer as a PoET node. Their reliance on Software Guard Extension (SGX), a feature that creates the certificate potential miners need to be accepted into the network, is only available in certain Intel processors. There is a wide range to choose from, so they don’t necessarily need to be expensive, but they are required.

A side-effect of this is that it means PoET blockchains must be permissioned so that only those who meet the requirements and are approved can join them. In contrast, most PoW blockchains are permissionless, which means they are open to all.

Advantages and disadvantages of PoET

The biggest advantage of PoET is its efficiency. Its fair lottery system, which allows nodes to sleep until they are chosen to process a new block, rather than forcing them to compete against other miners for the opportunity, means that PoET is extraordinarily less intensive than PoW. As a result, PoET nodes are also more affordable to run and more environmentally friendly.

PoET is also one of the only consensus mechanisms supported by a giant in the technology industry. While its existing implementation may not be perfect, Intel has the resources to keep on improving upon it and pushing it further, which means it could be even greater in the future.

The biggest disadvantage of PoET is that, because it calls for running trusted code in a secure environment, an Intel chip compatible with Software Guard Extension (SGX) is required. This goes against the decentralized and open approach to blockchain ecosystems that much of the industry has been advocating and working toward since its inception.

References

• Proof elapsed time cryptocurrency
• What proof elapsed time poet
• Software guard extensions