KeccakSHA3

KeccakSHA3 refers to the family of cryptographic hash functions based on the Keccak sponge function, and is commonly used to describe the SHA-3 implementations derived from Keccak. The SHA-3 standardization process, completed by NIST in 2015, created a separate path from the earlier SHA-2 line while preserving the underlying Keccak sponge core.

Keccak was designed by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche and submitted to NIST’s SHA-3 competition. It uses a sponge construction with a permutation (Keccak-f[1600] in practical forms) and supports fixed-output hashes as well as extendable-output functions. The design emphasizes resistance to length-extension attacks and flexible security levels through the rate and capacity parameters.

Standardization under FIPS 202 defines the SHA-3 family, including fixed-output variants SHA3-224, SHA3-256, SHA3-384, and SHA3-512, along with extendable-output functions SHAKE128 and SHAKE256. The padding rule pad10*1 and domain separation rules are specified to differentiate SHA-3 outputs from other uses of the same core. The standard also preserves the original Keccak core, but with specific padding and construction details chosen for interoperability and security assurances.

Variants and naming: while many libraries expose the term Keccak or KeccakSHA3, the formal standardized names are SHA3-xxx (and SHAKE-xxx for extendable-output). In practice, implementations may provide both Keccak-based and SHA-3 based interfaces that share the same underlying sponge core.

Usage and security: SHA3/Keccak variants offer hash outputs suitable for digital signatures, integrity checks, and authentication schemes. The security level generally matches the hash length, with no practical known weaknesses for the standard instances as of now.