The same and different between OptimismPBC and Arbitrum

The biggest difference between Optimism and Arbitrum is the implementation of the fraud proof mechanism.

The same and different between OptimismPBC and Arbitrum

Now is the time to bring @optimismPBC and @arbitrum to the forefront. Long time no see folks, we’ll start now!

Let’s look at what Optimism and Arbitrum have in common.

Both are Rollup, a true Layer 2 solution that stores all transaction data on Layer 1

Both are “optimistic”, i.e., they use fraud proofs

Both use sequencers for immediate “determinism”

Both have common cross-chain messaging capabilities that can be used to build advanced token bridges, such as @MakerDAO’s fast fetch bridge

The biggest difference between Optimism and Arbitrum is the implementation of proof of fraud, i.e., how to resolve a transaction after it has been executed if the status is disputed. That is, Layer 1 executes the entire Layer 2 transaction on the chain to verify the state root. This makes fraud proofs instantaneous, which is an advantage. However, there are some problems with it.

You need to supervise transaction execution, for which you need to use OVM (i.e. EVM rewritten to avoid side effects)

The gas usage of Layer 2 transactions must not exceed the gas cap of the Layer 1 blocks

You need to generate state roots on the chain for every transaction executed – leading to higher costs :(

There are security risks

Arbitrum uses multiple rounds of fraud proofs. Simply put, it finds the first opcode of the block that caused the disagreement via a dichotomous lookup. Once found, only this opcode is executed on the chain. The advantages of multi-round fraud proofs are as follows.

It simply generates a proof of state for a whole batch of transactions and publishes it to the chain

The Layer 1 block gas cap is not important because Layer 2 transactions are not executed entirely on Layer 1

The disadvantages are as follows.

Requires EVM -> AVM translation (fortunately automatic)

Slow – in the worst case, it can take up to 2 weeks to complete the fraud proof. Actually a week.

Requires original drawer to be online and cooperative

Thinking about it from another perspective, Optimism is containerized, while Arbitrum is virtualized.

Optimism’s approach has one major drawback. Imagine a hard fork that causes the Ether consensus rules to change and opcodes to be removed/repriced or modified. At that point, suddenly re-executing past transactions on Layer 1 would result in a very different final state. I don’t know how the Optimism team will solve this problem, but I think they will figure it out when the time comes. arbitrum has full control over the AVM specification, so there is no need to worry about such issues.

Both projects are trying to stay as close to the ethereum ecosystem as possible, but there are some differences. In general, you can still use the tools you know are related to EVM (solidity, hardhat, waffle, etc.). But it’s not that simple.

Optimism requires a special solidity compiler to generate the OVM bytecode. Therefore, it is only compatible with Solidity, and a specific version of Solidity at that. On the other hand, Optimism’s Layer 2 node is just a modified geth client, modified to improve compatibility.

On the surface, Arbitrum is fully compatible with the EVM/JSON RPC specification, but its nodes are custom implementations. arbitrum supports fraud proofs through automated EVM-> AVM translation. Thus, it supports any EVM language (vyper, YUL+, etc.).

Optimism uses weth and has a built-in wallet abstraction. arbitrum comes with ETH support.

Arbitrum provides a unified license-free bridge to bridge between arbitrary tokens and Layer 2 (it deploys a generic ERC20 contract as a Layer 2 counterparty.) Optimism prefers a dedicated bridge, but it is possible to build a generic bridge on Optimism.

The last difference is the live implementation. Arbitrum will go live with a “developer-facing mainnet” at the end of this month, while Optimism will wait until July.

Posted by:CoinYuppie,Reprinted with attribution to:
Coinyuppie is an open information publishing platform, all information provided is not related to the views and positions of coinyuppie, and does not constitute any investment and financial advice. Users are expected to carefully screen and prevent risks.

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