Vitalik Buterin Debates Over Blockchain Scaling Terminology

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Amid the rapidly evolving Ethereum ecosystem, Vitalik Buterin has rejoined the debate on the classification of layer-two scaling solutions, putting the spotlight on the security and scalability trade-offs between rollups and validiums.

Vitalik Buterin Weighs in on Ethereum Layer-Two Inclusion

Ethereum co-founder Vitalik Buterin has once again returned to a discussion within the blockchain community over the classification of layer-two scaling solutions. Much of the debate has centered around the distinction between various layer-two approaches, particularly focusing on the security aspects and architectural differences of various systems.

While the discussion has been ongoing for some time, see Buterin’s Oct. 2023 blogpost title “Different types of layer 2s,” Buterin’s recent involvement began when he responded to Daniel Wang, the founder of the Ethereum rollup solution Taiko, about how the source of data availability (DA) separates rollups from validiums.

This is correct.

The core of being a rollup is the unconditional security guarantee: you can get your assets out even if everyone else colludes against you. Can’t get that if DA is dependent on an external system.

But being a validium is a correct choice for many apps, and…

— vitalik.eth (@VitalikButerin) January 16, 2024

Validiums are a type of Ethereum layer-two scaling solution, which use zero-knowledge proofs for computational verification but differ crucially from rollups in data storage. Unlike rollups, where data is stored on the Ethereum main chain (layer-one), validiums store data on a separate server or system. This approach increases scalability but introduces potential risks with data availability, as any failure in the external system can render assets within the validium inaccessible. This makes validiums suitable for high-throughput applications but with added trust assumptions due to their reliance on external data storage systems.

Buterin pointed out that systems like validiums, which use separate data chains such as Celestia for data availability, do not offer the same level of security as traditional rollups. According to Buterin, the absence of a withdrawal guarantee in systems reliant on external solutions disqualifies them from being classified as genuine rollups.

The Ethereum co-founder referred to his previous attempts to categorize different layer solutions, noting the difficulty in neatly defining the terms due to the blurred lines between architecture and security. He observed that the distinction between layer-two and layer-three is more about architecture than security, complicating the categorization process.

Buterin’s remarks have sparked a discussion in the community, with differing opinions on what constitutes a layer-two network. While some argue that the reliance on external systems for data availability disqualifies validiums as true rollups, others maintain a broader definition. Ethereum community member Ryan Berckmans, for example, contends that any network settling on Ethereum should be considered layer-two, irrespective of the data availability approach.

This is a new industry, we can define “L2” to mean whatever we want. The maximally useful definition of L2 includes both rollups and validiums.

Later in the discussion, Buterin posted on Warpcast where he proposed new terminology to help encapsulate the differences between “strong L2” and “light L2” solutions. Examples of strong L2s were rollups, plasma, and channels; whereas validiums and pre-confirmations were light L2s. This new terminology was met with tepid responses.

The discussion is not just about semantics but also about understanding the trade-offs and security features of different blockchain scaling technologies. The way these technologies are categorized and understood affects how they are developed, used, and trusted.

Do you think rollups and validiums are layer-twos? Share your thoughts and opinions about this subject in the comments section below.