Merkle Tree

A Merkle Tree is a tree-shaped data structure in which cryptographic hash values are linked hierarchically. The lowest nodes represent hashes of individual data blocks; above them, several hash values are combined again and again until a root hash is formed at the top. If a data block changes, the associated path up to the root changes as well.

The advantage is that the integrity of large data volumes can be checked efficiently without having to compare every element in full. Merkle trees are therefore used in distributed systems, content addressing and other procedures in which changes are to be detected reliably and scalably. In backup architectures, too, they can help to verify the immutability of large data sets traceably.

A Merkle tree is thus a technical building block for cryptographic integrity checks. However, it replaces neither access protection nor structured Data Management or recovery tests, but complements them with efficient proof of data changes.