# Merkle tree

## Type of data structure / From Wikipedia, the free encyclopedia

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In cryptography and computer science, a **hash tree** or **Merkle tree** is a tree in which every "leaf" (node) is labelled with the cryptographic hash of a data block, and every node that is not a leaf (called a *branch*, *inner node*, or *inode*) is labelled with the cryptographic hash of the labels of its child nodes. A 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.

Demonstrating that a leaf node is a part of a given binary hash tree requires computing a number of hashes proportional to the logarithm of the number of leaf nodes in the tree.[1] Conversely, in a hash list, the number is proportional to the number of leaf nodes itself. A Merkle tree is therefore an efficient example of a cryptographic commitment scheme, in which the root of the tree is seen as a commitment and leaf nodes may be revealed and proven to be part of the original commitment^{[citation needed]}.

The concept of a hash tree is named after Ralph Merkle, who patented it in 1979.[2][3]