Designing for Decentralization

The goal of the Ethereum Roadmap is to increase the scalability of the Ethereum network without sacrificing decentralization. While some parts of the roadmap like the Surge focus on scalability without sacrificing security, the Verge focuses on allowing more people and more nodes to participate in validating the blockchain.

The Verge implements two technical upgrades:
1. Optimizing data storage by introducing Verkle trees
2. Extending decentralization through stateless clients

As Ethereum scales, it is particularly important to democratize access to the broadest number of network validators. The introduction of Verkle trees reduces the amount of data validators need to verify blocks, and stateless clients make it easier for validators to participate in the network. 

Designing for decentralization is designing for a secure, scalable network. 

Introducing Verkle Trees

The Ethereum state is a database of all accounts, smart contracts, balances, code, everything that is stored by the Ethereum blockchain. This massive database is currently just under 1TB in size and is accessed by all the contracts, users, and applications built on top of Ethereum. 

The Ethereum state currently uses Merkle-Patricia trees to effectively and securely encrypt the blockchain data. Merkle trees use large proofs (from 10MB up to 400MB) to efficiently verify the integrity of data while reducing the validator’s memory requirements.

A [Merkle tree or] hash tree allows efficient and secure verification of the contents of a large data structure. A hash tree is a generalization of a hash list and a hash chain.
Hash trees can be used to verify any kind of data stored, handled and transferred in and between computers. They can help ensure that data blocks received from other peers in a peer-to-peer network are received undamaged and unaltered, and even to check that the other peers do not lie and send fake blocks. –Wikipedia

The Verge introduces Verkle trees as an alternative to store the Ethereum state. Verkle trees use a similar tree-like structure to the Merkle-Patricia tree, but they make use of shorter proofs which are faster and easier to verify. 

“The key property that Verkle trees provide, however, is that they are much more efficient in proof size. If a tree contains a billion pieces of data, making a proof in a traditional binary Merkle tree would require about 1 kilobyte, but in a Verkle tree the proof would be less than 150 bytes - a reduction sufficient to make stateless clients finally viable in practice.” –Vitalik Buterin

The result of introducing Verkle trees is that validators can be much lighter, making way for stateless clients. 

Extending Decentralization with Stateless Clients

In order to participate in the Ethereum network as a validator today, you need to verify the entire Ethereum state by either downloading the entire state or by downloading and verifying block(n-1). In order to keep verifying, you need to have a local database which requires a large hard drive and the capacity to keep growing. 

With the introduction of Verkle proofs, instead of needing the entire database to verify the next block, you only need the pieces of the state that are read and written to in a particular block, along with a proof that proves that data is correct. Using Verkle proofs, you can verify a block without needing any other information regarding the Ethereum state. 

Due to the size of the Verkle proofs (less than 150 bytes) it is easier to run a node on the Ethereum blockchain and instead of validators needing to be Ethereum state clients, we can have stateless clients who are able to step in at any time to verify a block. 

The introduction of Verkle trees and stateless clients is a significant upgrade for the decentralization of Ethereum. After the Verge, anybody will be able to spin up a fresh node and start verifying blocks without having to download and verify the entire Ethereum state. 

Validators can be lightweight and distributed. It will be easier to set up a node, faster to verify, and less expensive since it won’t require heavy databases to store the state. 

The Verge makes it possible for everyone to participate in the network. By upgrading for decentralization, the Ethereum network can continue to grow and scale.