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Merkle Proof

Sam Ingalls
Last Updated January 24, 2022 8:19 am

Merkle proofs describe the verification process for identifying the components of cryptographic data structures known as Merkle trees. Merkle proofs are essential to distributed computing networks like blockchain applications and cryptocurrency, which rely on Merkle hash trees for validating block data.

This article looks at the definition of a Merkle proof and how the validation method works.

What is a Merkle Proof?

A Merkle proof confirms specific transactions represented by a leaf or branch hash within a Merkle hash root. Merkle proofs are an example of inclusion proof because it allows senders and receivers to verify specific data contained in a large dataset.

How Do Merkle Proofs Work?

Merkle roots reflect the combined hashes of a block of data. Through the unified hash, devices can validate a particular set of transactions. Additional changes to transactions are easily identifiable as any alteration to node (leaf and branch) hashes changes the hash root.

In the below example, the root hash (ABCD) reflects the Merkle tree’s combined hashes represented by hashes for leaves (A, B, C, and D) and branches (AB and CD).

A graphic image showing a Merkle tree with its component branches which break into leaf hashes and they're representative data known as transactions.

Merkle proofs verify the inclusion of a specific transaction, like the hash for Leaf C, by climbing the hash tree from transaction to root. By validating the existence of the Branch CD and the Root ABCD, devices can prove the data reflected by Transaction C exists within the block.

Use Cases of Merkle Proofs

Patented by computer science pioneer Ralph Merkle in 1979, Merkle trees and proofs are widely used in distributed computing systems like:

  • BitTorrent
  • Blockchain and cryptocurrency
  • InterPlanetary file system (IPFS)
  • Peer-to-peer networks
  • ZFS file system

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