Merkle Tree
A Merkle tree is a hash-based data structure that lets many pieces of data be verified efficiently and securely.
A Merkle tree is a way to organize data by repeatedly hashing pairs of items until only one hash remains, called the Merkle root. Each leaf of the tree represents a hash of a transaction or data item, and each higher branch is a hash of the two hashes below it. Because cryptographic hashes change dramatically if the input changes, even a tiny alteration to one item produces a different root.
Merkle trees matter in crypto because they let systems prove that specific data is included in a larger set without downloading or checking the entire set. In Bitcoin and many other blockchains, transactions in a block are summarized by a Merkle root stored in the block header. A lightweight wallet can verify that a transaction is in a block using a short Merkle proof, instead of fetching every transaction in that block. A useful comparison is a sealed packing list: you can confirm one package belongs in a shipment by checking a small chain of confirmations, rather than opening every box.
Other terms in Cryptography & Privacy
CoinJoin
A privacy technique that combines multiple users’ cryptocurrency payments into one transaction to make input-output links harder to trace.
Crypto Mixer
A service or protocol that blends cryptocurrency from many users to make transaction trails harder to trace on a public blockchain.
Digital Signature
A digital signature is cryptographic proof that a message or transaction was approved by the holder of a specific private key.
Fully Homomorphic Encryption
A cryptographic method that lets data be processed while still encrypted, so only the key holder can reveal the final result.