Verkle tree structure
Understanding the Verkle Tree Structure
The Verkle tree is a commitment scheme that has gained significant attention in the realm of blockchain technology and data storage. It is designed to be more efficient than traditional Merkle trees, allowing for wider branching factors and smaller witnesses. In this article, we will delve into the concrete layout of the draft Verkle tree EIP, providing a comprehensive overview of its structure and functionality.
Overview of the Verkle Tree EIP
The Verkle tree EIP introduces several significant changes to the traditional tree structure. These changes include:
- A switch from 20-byte keys to 32-byte keys
- The merge of the account and storage tries
- The introduction of the Verkle trie itself, which uses vector commitments instead of hashes
Vector Commitments and Pedersen Commitments
The Verkle tree uses Pedersen commitments as its vector commitment scheme. Pedersen commitments are based on elliptic curves and are designed to be efficient and secure. The curve used in the Verkle tree is Bandersnatch, which was chosen for its performance and ability to support efficient SNARKs in BLS12_381.
Layout of the Verkle Tree
The Verkle tree is composed of two types of nodes: extension nodes and internal nodes. Extension nodes represent 256 values with the same stem but different suffixes, while internal nodes have up to 256 children, which can be either other internal nodes or extension nodes.
Commitment to Extension Nodes
The commitment to an extension node is a commitment to a 4-element vector, with the remaining positions being 0. This commitment is composed of an "extension marker," which is just the number 1, the two subtree commitments C₁ and C₂, and the stem of the key leading to this extension node.
Commitment to Internal Nodes
Internal nodes have a simpler calculation method for their commitments. The node is seen as a vector of 256 values, which are the (field representation of the) root commitment of each of their 256 subtrees. The commitment for an empty subtree is 0, and if the subtree is not empty, the commitment for the internal node is the sum of the commitments of its children.
Insertion into the Tree
Insertion into the Verkle tree involves adding a new value to the tree, which can get interesting when the stems collide on several initial bytes. The process involves adding internal nodes until the differing byte, and then inserting another "extension-and-suffix" tree with a full 31-byte stem.
Shallower Trees, Smaller Proofs
The Verkle tree structure makes for shallower trees, which reduces the amount of stored data. Its real power, however, comes from the ability to produce smaller proofs, i.e., witnesses. This will be explained in the next article.
Practical Implications
The Verkle tree has several practical implications for blockchain technology and data storage. Its ability to produce smaller proofs makes it an attractive solution for applications that require efficient and secure data storage. Additionally, its ability to handle wider branching factors makes it a more scalable solution than traditional Merkle trees.
Forward-Looking Thoughts
The Verkle tree is a promising solution for the challenges faced by blockchain technology and data storage. Its ability to produce smaller proofs and handle wider branching factors makes it an attractive solution for a wide range of applications. As the technology continues to evolve, it will be exciting to see how the Verkle tree is adopted and integrated into real-world systems.
Conclusion
In conclusion, the Verkle tree is a commitment scheme that has gained significant attention in the realm of blockchain technology and data storage. Its ability to produce smaller proofs and handle wider branching factors makes it a more efficient and scalable solution than traditional Merkle trees. As the technology continues to evolve, it will be exciting to see how the Verkle tree is adopted and integrated into real-world systems.
Source: https://blog.ethereum.org/en/2021/12/02/verkle-tree-structure
