Hash

A hash is the output of a cryptographic function that maps any input — a sentence, a file, a whole block — to a fixed-length string. Change one bit of input and the hash changes completely; you can’t reverse a hash to recover its input.

Where hashes appear in crypto

Each block references the hash of the block before it, chaining the whole ledger together (hence “blockchain”). Mining is a search for a hash below a target value. Wallet addresses and transaction IDs are also hash-derived. Hashes make tampering visible.

Why it decentralizes trust

Because any node can hash a block and instantly verify it matches its neighbor, nobody must trust a central authority’s bookkeeping. Verification stays cheap and open at every point of the network.

Related terms

Blockchain, Mining, Proof of Work, Node, Merkle Tree