Single-slot Finality: Vitalik Buterin Has Updated Ethereum’s Roadmap

[TL; DR]

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1. Vitalik published an article on January 25, 2021, introducing the latest roadmap for the development of Ethereum saying that Ethereum will turn to single-slot finality.
2. Generally, the first block of each period is the checkpoint on the beacon chain. Once a checkpoint is finalized, all the blocks before it are also determined and cannot be tampered with.
3. Both efficiency and security depend on the length of confirmation time. The longer the confirmation time, the more time will be taken to check the security of the trading, but the less efficiently the system will operate.
4. Based on the Gasper consensus algorithm, Ethereum is more secure than ordinary blockchains utilizing the longest chain algorithm.
5. Following the PoS consensus mechanism and the realization of sharding and Verkle tree optimization, Ethereum will switch to develop and research the single-slot finality.

In January, Ethereum founder Vitalik Buterin introduced his latest development roadmap for Ethereum in his article titled Paths toward single-slot finality published on ethereum.org.

The last Gate.io article introduced the specific plan for the upgrade and expansion of Ethereum and explained the PoS consensus mechanism that the new Ethereum relies on. It also introduced the operation of the beacon chain. This article will continue to cover the finality of blocks in the beacon chain and why Vitalik believes that it is necessary for Ethereum to be upgraded to a single-slot finality model.


Finality Issues of Beacon Chain

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On the beacon chain, there are a series of checkpoints that are used to finalize the on-chain content. Generally, blocks in the first slot of each epoch are checkpoints. When the committee votes on the blocks in the time slot, it also needs to vote on the checkpoints of the corresponding time slot. When a period (A) ends, the corresponding checkpoint wins the support from a supermajority (more than 2/3 of the remaining total validator) and the period (A) is justified. And the next period (A+1) after period (A) has also been proved, which can be said that period A has been finalized. Once a checkpoint is finalized, all the blocks before it are also determined and cannot be tampered with.

To explain from the user’s point of view, before a transaction can be submitted, it needs to go through a series of processes including being packaged into blocks, proposed by the proposer, verified by the verifier, certified, and finally finalized. All this takes 64 to 95 time slots (about 15 minutes on average). If the time slot of the transaction is just before the checkpoint and it is finalized at the fastest speed, the time required will be 64 time slots; if the time slot of the transaction is just after the checkpoint and it is finalized at the slowest speed, the time required will be 95 time slots. Both efficiency and security depend on the length of confirmation time. The longer the confirmation time, the more time will be taken to check the security of the trade, but the less efficiently the system will operate.


The committee needs to vote three times
As a result, the committee needs to conduct three votes. The first is to vote on the block in the most recent time slot to select the latest block on the beacon chain. The LMD GHOST (Latest Message Driven: Greediest Heaviest Observed SubTree) algorithm is used in this vote. The LMD refers to "Latest Message Driven" and "GHOST" refers to "Greedy Heaviest Observed Subtree". Through this fork algorithm, the network will give the same result as the longest chain rule in a safer way, and get a "main chain" or "canonical chain".

The second is to vote on checkpoints of time periods to prove and finalize on-chain information. The Casper FFG algorithm (Casper, the Friendly Finality Gadget) is used in this vote. Casper and GHOST are called Gasper in Ethereum, and together they constitute the core consensus protocol of Ethereum. The last is the Crosslink Vote used to connect the shard chain to the beacon chain. All voting information will be written into the Attestation.



Ethereum's vision for single-slot finality

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Vitalik wrote in his article that Ethereum based on the Gasper consensus algorithm is more secure than ordinary blockchains using the longest chain algorithm. To tamper with the information in the finalized block will cost over 3 million ETH. However, users still think a 15-minute finalization is too long to bear and are calling for new confirmation methods that are both efficient and secure. Moreover, single-slot finality can also reduce the possibility of miners extracting MEV by rearranging transactions. It can also help to simplify the protocol and, as a result, reduce system bugs.

Vitalik proposed two approaches to optimize the Ethereum consensus algorithm to achieve single-slot finality.

First, all validators are currently required to join Casper FFG voting. This perhaps can elect a medium-sized super committee of only a few thousand validators, with consensus and finality taking place in a single slot. If the committee fails to complete the confirmation, the system will continue to confirm the latest block based on the original LMD GHOST rules. The committee size would need to hold around 3 million ETH or have 97,152 validators to become a relatively secure super one, according to estimation.


Second, it could be possible to let as many provers as possible play a role. The hurdle of this scheme lies in how to aggregate a large number of signatures in a short period of time. If it requires a staker group of about 4 million ETH, that is, 131,072 stakers, a total of 131,072 signatures will have to be aggregated quickly. Vitalik believes that the signature aggregation service is likely to be significantly optimized in the next two years.


Conclusion

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Following the PoS consensus mechanism and the realization of sharding and Verkle tree optimization, Ethereum will switch to develop and research the single-slot finality, which will take over 1 year to complete. Thanks to the efforts of its developers, Ethereum will be constantly upgraded. And this will enable ordinary users to enjoy safer and more convenient decentralized services.


Author: Gate.io Observer: Edward. H
* This article represents only the views of the observers and does not constitute any investment suggestions.
*Gate.io reserves all rights to this article. Reposting of the article will be permitted provided Gate.io is referenced. In all other cases, legal action will be taken due to copyright infringement.


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