The latest thinking on expansion by Buterin and the Ethereum Foundation

On July 7, 2022, the Ethereum Foundation research team held their eighth AMA on Reddit. ECN organized and compiled most of the questions for this AMA. It should be noted that members of the Foundation R&D team have personal opinions and speculations on certain topics. To avoid misinterpretation, please refer to the original post.

Due to the length of the article, the articles are organized by topic, and this article is a topic of expansion.

JonCharbonneau asked:

Can you explain how enshrined rollups work and their potential development path in Ethereum? (optimistic and zkEVM?)

(Translator’s Note: L2 scaling researcher Polynya explained in this tweet the difference between “enshrined rollups” vs. “discrete rollups” is like “public sector” and “private sector”.)

And what do you think is the biggest good and bad thing this can bring, because there are a lot of people with different opinions on this.

Ethereum Foundation Justin Drake replied:

“Enshrined rollups” is a very interesting topic :) “Enshrined rollups” refers to rollups that enjoy some kind of consensus integration on L1. And smart contract rollups (see  the examples listed in L2Beat  and  zkrollups.xyz  ) are different – run entirely on L2, outside of consensus.

Consensus integration can give enshrined rollups super capabilities, but comes at a significant cost – see below for a detailed discussion of the benefits and drawbacks. Broadly, enshrined rollups and smart contract rollups are complementary. I hope both will play a key role in the rollup-centric Ethereum roadmap.

Their potential development path in Ethereum (optimistic and zkEVM?)

The current plan is to develop directly in the direction of enshrined zk-rollup. This is part  of the visualization roadmap “generating ZK-SNARK proofs for everything” published by Vitalik. The Ethereum Foundation has a team of about 10 people led by Barry Whitehat working on upgrading the canonical EVM instance to an enshrined zkEVM rollup. That is to say, construct a zkEVM whose state root is completely equivalent to provide concise cryptographic proofs (SNARKs) for L1 Ethereum blocks, proving that the corresponding state root is valid. This brings various benefits:

No re-execution : Validators and other full nodes no longer need to re-execute transactions to validate a block. This removes the consensus bottleneck of computation for validators and may be an opportunity to increase the EVM gas limit. Removing the need for re-execution also speeds up most synchronization strategies.

Consensus is cleaner : Removing execution from consensus means validators can run ultra-simple execution clients where tens of thousands of consensus-critical EVM execution code is reduced to a few hundred lines of SNARK validation code.

No need for state witnesses : stateless execution clients no longer need to download witnesses (such as Merkle paths or Verkle proofs) – downloading state differences is sufficient. This greatly improves the validator’s consensus bandwidth efficiency and frees up higher EVM gas limits.

Safer light clients : Light clients can filter out invalid state roots quickly, not as slowly as using fraud proofs to filter out invalid state roots. This makes the “Ethereum-L1” bridge more secure.

Upgrading a current single-instance EVM to an enshrined rollup is a huge undertaking that will take years. The relatively easy step after that is to deploy multiple (eg 64) parallel enshrined zkEVM instances (consuming blob data). This is a form of L1 homogenization execution sharding (previously known as “Phase 2”).

Enshrined zkEVM’s engineering work is especially interesting for tech fans, and it involves cryptographic proof systems, circuit design and auditing, and software and hardware acceleration. The EF team is hiring engineers for zkEVM – please contact  justin@ethereum.org

What are the biggest pros and cons

benefit

Social Consensus : Enshrined rollups inherit the social consensus of L1 and no longer require governance tokens to perform rollup upgrades. By contrast, most smart contract rollups are likely to be subject to governance attacks.

Subsidized Proof Verification : Enshrined rollups can subsidize the cost of proof verification for settlement (fixed cost per block). Instead, the smart contract rollup must pay EVM gas for settlement. Settlement delays: Enshrined rollups naturally benefit from per-block settlement delays.

Optimal liveness : Many smart contract rollups may choose to utilize external consensus mechanisms for ordering transactions, and as an on-chain escape hatch. This ordering infrastructure suffers from suboptimal liveness, as external consensus can fail and escape pods will only activate after a timeout.

EVM state root equivalence : Enshrined zkEVM’s tools and light clients work out of the box. Many smart contract rollups may choose not to have EVM state root equivalence, but a Solidity-compatible VM (eg, zkSync) or a bytecode equivalent EVM (eg, Scroll).

Network Effects : Canonical EVM instances enjoy the network effects of being a first mover, and upgrading to enshrined preserves those network effects.

harm

No Public Goods Funding : Enshrined zkEVM rollups will have limited discretion in funding public goods. Unlike Optimism, which has a governance mechanism for funding any public good, enshrined zkEVMs will be limited to funding L1 security and contributing to the scarcity of ETH.

Suboptimal compression : A smart contract rollup may choose to settle on-chain rather than once per block, allowing for better data compression. Smart contract rollups can also have a custom or frequently updated dictionary to improve data compression.

Virtual machines lack flexibility : An Ethereum enshrined VM is likely to be an EVM. In contrast, a smart contract rollup can choose to adopt a more commonly used VM (eg, WASM, RiscV, MIPS) or create a new VM (eg, Cairo). A custom zkVM may achieve better data compression than zkEVM.

Harder pre-confirmation : A smart contract rollup can choose a centralized sequencer to provide instant (~100ms) pre-confirmation to give users a good interactive experience. Such fast pre-confirmation is difficult to achieve using a decentralized sequencing system, whether enshrined rollups or smart contract rollups.

Latecomers : Due to the slow and conservative nature of L1, the enshrined zkEVM will be a so-called latecomer. To hedge against the possibility of circuit vulnerabilities, a redundant multi-circuit setup or cumbersome formal verification may be required.

TheTrueBlueTJ asks:

In theory, is it possible for a global payment system to use Ethereum as the currency of circulation? Either through L1 or rollup? Of course, future scalability improvements are to be taken into account.

Ethereum Foundation Justin Drake replied:

It’s entirely possible. Ethereum can currently reach 10 TPS (transactions per second), which is a rough order of magnitude. And in the future there will be 3 100x increases that will bring us to 10 million TPS (enough for 100 transactions per person per day):

100x growth comes from rollups;

100x growth comes from sharding;

100-fold increase in bandwidth in 10 years (Nielsen’s Law).

My thesis is that demand for the safest shared security platform will saturate due to network effects. A plausible move is that if Ethereum can maintain its lead in economic security and scale to 10 million TPS at the same time, then Ethereum has the potential to serve as the settlement layer of the Internet.

AllwaysBuyCheap asked:

How does the increase in bandwidth increase the transaction speed of Ethereum? More block space?

Ethereum Foundation Justin Drake replied:

There are various computational bottlenecks in consensus:

Disk I/O: removed by stateless (and enshrined zkEVMs);

Storage: removed by stateless (and enshrined zkEVMs);

Computation: removed by enshrined zkEVMs;

Bandwidth: Essential.

Because bandwidth is the fundamental consensus bottleneck, an increase in bandwidth can free up more block space.

not_a_disaster asked:

What is better in the long run? Will a single rollup dominate or are there several smaller rollup scenarios?

The arguments I see on both sides are:

1. A dominant rollup means users don’t need to bridge assets and have a better user experience

2. However, if there is a dominant rollup, then the other L2s are meaningless. But then again, in the long run, the EF team has been promoting only zkRollup (ideally with zkEVM).

Ethereum Foundation Ansgar Dietrichs replied:

This is a good question! Any chain that scales its throughput to a certain level (L1 or L2) will make it impossible for normal users to fully verify the chain. The main difference between L1 and L2 is that L2 can make use of its underlying base layer to make up for this:

1. On zk-rollups, the base layer ensures the validity of state transitions and the availability of corresponding data. If you can’t handle the rollup transaction yourself, the only guarantee is that you have access to the current state (so that you can send a valid rollup transaction). So the only additional trust assumption is the existence of a state provider (centralized or decentralized).

2. Optimistic rollup introduces a small additional trust assumption. Not only do you need to trust that someone is processing the rollup transaction and making the current state available, but you also need to trust that in the event of a fraudulent state transition, at least one of those entities processing the rollup will submit a corresponding fraud proof. Usually optimistic rollups give people some financial incentive to submit these fraud proofs, so this is very little different from zk-rollups.

Conceptually, rollup can be scaled without breaking too much trust because of the relationship between L1 and L2. As long as users trust the state of the base layer, they can distinguish between correct and incorrect L2 behavior (eg, the state provider’s response will always be accompanied by a proof against the rollup state root, which is stored on L1).

On the other hand, for the base chain, it is very important that each user can handle the chain by himself. If you don’t run your own node and ask an external state provider for the state, you can’t tell if the provided state is real. Similarly, if there are malicious state transitions, there is no settlement layer that can resolve disputes – you have to choose for yourself which side to trust.

All of these reasons led us to decide to turn Ethereum L1 into a rollup settlement layer with a focus on making it easy for every user to process transactions. I’m personally very excited about the imminent transition to Verkle trees, which will allow for a fully stateless client-side implementation (imagine your Metamask being able to run its own embedded node). In this way, over time, the base layer becomes the “root of trust” for the L2 ecosystem.

Hopefully my answer explains why rollup’s throughput has the potential to far exceed L1’s without making unreasonable trust tradeoffs. So I personally expect to have very high throughput L2 at the end. However, it remains to be seen whether there will be a single dominant rollup.

Ethereum Foundation Justin Drake replied:

What is better in the long run? Will a single rollup dominate or are there several smaller rollup scenarios?

In the long run, rollup will be able to handle millions of transactions per second, so parallelism is necessary. We can envision a kind of internal rollup parallelism (eg, via a multicore rollup VM) and a kind of rollup external parallelism (eg, parallel instances of the same VM).

zk-rollups that share security (e.g., zk-rollups that share the same data availability) are synchronously composable, so the line between “rollup internal parallelism” and “rollup external parallelism” starts to blur, and so does the end result Not too far.

not_a_disaster asked:

What do you think are the problems with application-specific L2/rollup?

If now a Web2 company with a large user base (10M – 100M users) wants to use the blockchain, but still wants to achieve decentralization, then application-specific chains/rollups are pretty much the only good alternative options.

What do you think are the downsides of doing this?

Ethereum Foundation Justin Drake replied:

What do you think are the problems with application-specific L2/rollup?

Instead of deploying an application-specific rollup, I encourage developers to build applications based on general-purpose rollups (eg, Arbitrum, Optimism; soon zk rollups). This will speed up development, amortize settlement overhead, promote composability, and reduce tool friction. Having said that, the vision of a general-purpose rollup certainly has its pitfalls.

Rollup will be vulnerable to attack. We’ve had exchange attacks that cost tens of millions of dollars, and cross-chain bridging attacks that cost hundreds of millions of dollars – with billions of dollars in rollups expected. Between the implementation of EIP-4844 or EIP-4488, transaction fees will not be as low as we would like. Tools will underperform over time, and network effects may slowly kick in.

Vitalik replied:

If now a Web2 company with a large user base (10M – 100M users) wants to use the blockchain, but still wants to achieve decentralization, then application-specific chains/rollups are pretty much the only good alternative options.

I think in this case they should use  validium . They will rely on a centralized server or a committee for liveness, but they can be subject to the security guarantees provided by the blockchain.

AllwaysBuyCheap asked:

Why was EIP-4488 not implemented while EIP-4844 was being developed? Which technology do you think will win in the long run, Snarks or Starks?

Vitalik replied:

STARKs are a quantum proof, they have better proof times and more flexibility in the domain you use.

SNARK turns out to be much smaller. I expect pre-quantum, SNARKs, and in some cases SNARKs of STARKs (with the advantages of STARKs but much smaller proof sizes) will dominate, and post-quantum STARKs will dominate. But different people have different opinions on this.

Ethereum Foundation Justin Drake replied:

Why was EIP-4488 not implemented while EIP-4844 was being developed?

As you pointed out, EIP-4844 and EIP-4488 are not mutually exclusive. I tend to implement EIP-4488 shortly after the merger, and before EIP-4844. Because EIP-4844 will take years to bear usable fruit. In fact, even after EIP-4844 goes live on mainnet, we may have to wait a few months before rollup actually chooses to use bolob data.

Which technology do you think will win in the long run, Snarks or Starks?

Long-term, what we want is a post-quantum SNARK. This advanced post-quantum SNARK is hash-based and happens to be a STARK, i.e., a transparent SNARK (“transparent” means no trusted initialization is required).

egodestroyer2 asked:

How do you predict the near-term, medium-term and long-term fee market for L2 to start settling transactions and taking business off the main chain?

Ethereum Foundation Justin Drake replied:     

The fee market is volatile and positively correlated with ETH prices. As such, the forecast fee market is largely guesswork.

In the short term (July, August, September), I expect the fee market to remain relatively calm in a bear market;

In the near term (i.e. a few months after the merger), I expect Ethereum and ETH to heat up and the fee market to grow significantly;

In the medium term (i.e. 2-3 years), gas prices may calm down temporarily as rollup is heavily adopted and supply of block space exceeds demand In the long term (3-10 years), due to rollup and sharding, I Expect small per-transaction fees, but a high total fee volume (likely $1 billion/day).

Posted by:CoinYuppie,Reprinted with attribution to:https://coinyuppie.com/the-latest-thinking-on-expansion-by-buterin-and-the-ethereum-foundation/
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