Cryptographic Hash

A cryptographic hash is the output produced by applying a cryptographic hash function to data. It represents the input as a fixed-size value and is used for integrity verification, data structures, and other cryptographic mechanisms.

A secure cryptographic hash function should make it computationally impractical to recover suitable original data from the hash alone. It should also be difficult to find two different inputs that produce the same result, known as a collision.

Hashes are fundamental to blockchains. For example, a previous block's hash may be included in the header of the next block, creating a cryptographic connection between blocks. Changing historical data changes the corresponding hash and breaks this relationship.

In Proof-of-Work, cryptographic hashes are used to search for values satisfying a network-defined difficulty condition. This creates the computational cost associated with block production.

Cryptographic hashes are also used together with digital signatures. Instead of signing a large data set directly, systems can often sign a compact cryptographic representation of that data.