Keccak-256 is a cryptographic hash function used widely in the Ethereum ecosystem and related tooling.
Keccak-256 outputs a 256-bit digest and is used for address derivation, logs/topics, and contract selectors in Ethereum-like environments. It's similar to standardized SHA-3 but differs in padding details.
"Function selectors are the first 4 bytes of the Keccak-256 hash of the signature string."
"Event topics in logs use Keccak-256 of the event signature for indexing."
Ethereum's keccak differs from NIST SHA-3 due to padding; implementations must use the correct variant for compatibility.
"Using SHA3-256 instead of Keccak-256 produces different digests and breaks address calculations."
"Ethash combines Keccak and memory-hard steps for PoW, while Keccak-256 alone is a general-purpose hash."
All terms and definitions may update as the Cryptionary improves.