Hash

A hash is an output, while a hash function is the algorithm producing it. SHA-256 and Keccak-256 produce 256-bit outputs. Since inputs can have different sizes, collisions mathematically exist; collision resistance makes finding them difficult.

Blockchain networks use hashes to link blocks and commit to datasets. Changing data and recomputing normally changes the hash. A match checks integrity against a known reference, but does not prove that the original data was true.

Hashing is not encryption and cannot be decrypted to recover content. Guessable data can be discovered by testing possible inputs. Password storage requires dedicated derivation functions and additional measures; a fast hash alone is insufficient protection.