Vitalik’s recent statement about multichain and cross chain has aroused heated discussion. Vitalik claimed that while he is optimistic about a multi-chain blockchain ecosystem, he is still pessimistic about cross-chain applications and the fundamental security limits of bridges are the key reason.
Multichain vs cross chain, a good question indeed. However I’m afraid I have to say Vitalik jumped to the conclusions.
We obviously cannot deny the importance and necessity of cross chain bridges in the separate blockchain ecosystems simply because there may lies security limits. The prevalence of splits in blockchains make the market being desperate for safe and reliable cross-chain solutions.
In addition, how do we know the blockchains are unable to solve their security issues in the future? Every blockchain takes security as their top priority just like Bitcoin. Without saying, it is unwise to say cross chain will not be the future simply because the blockchains are unsafe.
Cross-chain is necessary for current and future blockchain ecosystems
Vitalik asserted that “there really are a few separate communities with different values and it's better for them to live separately than all fight over influence on the same thing”, so he insisted that multi-chain in the future is inevitable.
Multichain is not the future, it is what is happening right now. Today’s blockchains show certain differences in terms of underlying techniques, economic models, community organizations and etc. Following the rules and philosophy of development, if a community/ an ecosystem expects to grow bigger, it is impossible to make it by entertaining itself without interactions with outside world. That’s why cross chain bridges came into being and have become an indispensable tool for blockchains development.
Blockchains should solve the security problems within their ecosystem by themselves
When the blockchains cannot solve its own security problems within zones of sovereignty, this issue will definitely spread on a larger scale. But to be clear, it is not spread by cross chain bridges.
Decentralized blockchain ecosystem consists of the underlying blockchain and the applications built on the blockchain. They, no matter the underlying blockchain or the applications, have deployed security guarantees which are closely related and dynamically interacted. In such case, if the underlying chain is not secure, the applications built-upon will not be safe and sound. But if we go with the conclusion made by Vitalik, then the applications should not be built on the underlying chain at the very beginning, nor should their data and assets interact with the underlying chain.
Blockchain security problems may be resolved with outside assistance
Vitalik took Ethereum is 51% attacked as an example, "If Ethereum is 51% attacked and recovers, Arbitrum and Optimism will recover, so even if Ethereum is 51% attacked, the 'cross- Rollup’ applications are also guaranteed to be consistent”. My question is, how is Vitalik sure that cross chain bridges cannot recover from attack?
Hard fork is the only solution to recover from 51% attack. But hard fork has tremendous impact on both underlying blockchain and its built-upon applications.
According to the above logic, if there is a problem occurring within one of the blockchain bridged by the cross-chain, we can easily solve it by building a larger "ecosystem" at the other side of the bridge.
Bitcoin system not only requires users to sign the transaction, but also requires both parties to confirm every steps of transactions. Cross-chain bridge can also track all assets, but this will undoubtedly waste transaction processing time and consume more resources.
Vitalik held that, “No one will 51% attack Ethereum just to steal 100 Solana-WETH (or, for that matter, 51% attack Solana just to steal 100 Ethereum-WSOL). But if there's 10 million ETH or SOL in the bridge, then the motivation to make an attack becomes much higher, and large pools may well coordinate to make the attack happen.” This is true. No one is going to do a 51% attack on Ethereum for 100 Solana-WETH, but someone will attack Ethereum for 10 million ETH or more. From this perspective, the security threats faced by Ethereum and other public blockchain ecosystems are not necessarily less than cross-chain bridges. It cannot be asserted that the cross-chain bridge faces greater security risks just because there are many assets locked in the cross-chain bridge.
The future blockchain world will inevitably be a multi-chain world, and each chain will also have its own ecosystem. Say NO to cross chain will only result in the unhealthy and inflexible ecosystem.