In a recent blog post, Ethereum’s co-founder, Vitalik Buterin, discussed potential enhancements to the Plasma chains aimed at bolstering the security of Web3.
His analysis delves into the strengths and weaknesses of the current system, offering proposed adjustments to elevate Plasma’s standing within the industry.
Plasma chain is a separate blockchain anchored to Ethereum Mainnet but executing transactions off-chain with its mechanism for block validation.
It is designed to improve the scalability of blockchain platforms such as Ethereum by composing blockchains into a tree hierarchy where each child chain connects to the main Ethereum blockchain.
Plasma chains can perform the computation of smart contracts to reduce the demand on the root blockchain, while the root chain serves as a trust and arbitration layer that maintains data integrity and security for the entire network.
Weaknesses of Plasma
Vitalik noted that despite its initial promise, Plasma’s significance has waned over time, primarily due to two key factors, leading to the ascendancy of rollups in the blockchain landscape.
Firstly, he highlighted the substantial costs associated with client-side data storage in Plasma. This expense has become a notable drawback, affecting the overall efficiency and practicality of the Plasma chain.
Secondly, he pointed out inherent limitations within the Plasma framework, making it challenging to extend its applications beyond payment-related functions. Rollups, on the other hand, have emerged as a more versatile and scalable alternative.
Generalizing to Fungible Tokens
He further added that while Plasma works well for NFTs, applying it to fungible tokens like ETH and USDC poses challenges due to high gas costs.
One solution involves treating adjacent coins as a single unit, but this leads to fragmentation issues. However, if a UTXO model is used, it’ll require users to provide the last week’s history when withdrawing assets.
He also noted that the challenge of generalizing Plasma to the Ethereum Virtual Machine (EVM) involves overcoming various obstacles. One key difficulty arises from the fact that many state objects within the EVM lack clear ownership structures.
In traditional blockchain systems, ownership is well-defined for each state object, but within the Ethereum Virtual Machine, this clarity is often absent.
Furthermore, the EVM’s unbounded dependencies present a complicating factor in the extension of Plasma. Unbounded dependencies refer to the complex relationships and interdependencies among different elements within the EVM.
This intricate network of dependencies makes it challenging to design effective exit games, which are mechanisms that facilitate the secure withdrawal of assets from the Plasma chain to the main Ethereum chain.
The challenge also encompasses the lack of aligned incentives for proving validity within the EVM context. Unlike UTXO-based systems, where ownership and validity are more straightforward, the EVM’s design introduces complexities in ensuring that proofs of validity are appropriately incentivized.
The absence of guarantees, which are inherent in systems based on Unspent Transaction Outputs (UTXOs), further complicates the task of adapting Plasma to the Ethereum Virtual Machine.
How to enhance Plasma
To make Plasma a better option for the Web3 space, Vitalik proposed the use of validity proofs. Validity proofs, also known as zero-knowledge (ZK) proofs, are cryptographic techniques used in the context of zero-knowledge rollups (zk-Rollups) on Layer 2 blockchains to demonstrate the accuracy and legitimacy of data summarized on the Layer 1 chain.
These proofs are employed to verify that the state transitions are correct, ensuring that the blockchain accurately represents the Layer 2 state.
Validity proofs are essential for maintaining the integrity and trustworthiness of Layer 2 transactions and state transitions.
They play a crucial role in ensuring the accuracy and legitimacy of off-chain computations and state updates, contributing to the overall security and reliability of Layer 2 blockchain networks.
He added that the introduction of validity proofs offers a versatile toolkit for creating a blockchain network resembling Plasma that is compatible with the Ethereum Virtual Machine (EVM).
However, he said that the recognition that Plasma security guarantees may not extend to cover all users indicates that there are limitations and challenges within the Plasma design.
While Plasma offers certain security assurances, especially in terms of transaction validity and asset protection, these assurances might not be universally applicable to all users or scenarios.
These challenges are deeply rooted in the complexity of extending Plasma-style exit games to a diverse range of intricate applications. Despite these challenges and the recognition that Plasma-style exit games may face limitations in addressing the needs of various complex applications, he believes that a substantial percentage of assets can still be effectively secured in practical scenarios.
In concluding his argument, the co-founder noted that while rollups are currently considered the gold standard with unmatched security properties, Plasma offers a distinctive advantage by effectively bypassing the data availability question. This unique attribute of Plasma results in a significant reduction in transaction fees.
Also, Plasma, despite being considered an underrated design space in 2023, has the potential to serve as a substantial security enhancement for blockchain networks that might otherwise adopt the validium model.
The co-founder notes that the emergence of Zero-Knowledge Ethereum Virtual Machines (ZK-EVMs) in the current year presents an opportune moment to revisit and further explore the design possibilities within the Plasma framework.
