SHA-3

SHA-3 is the cryptographic hash standard published by NIST in FIPS 202, based on the Keccak sponge construction selected through a public competition that concluded in 2012. It defines four fixed-output functions (SHA3-224 through SHA3-512) and two extendable-output functions, SHAKE128 and SHAKE256, which produce a digest of any requested length.

#Use in post-quantum standards

The SHAKE extendable-output functions are used heavily inside NIST's post-quantum schemes. ML-KEM applies SHAKE for hashing and as a pseudorandom generator during key encapsulation, and SLH-DSA uses the SHA-3 and SHAKE family as the underlying hash in its stateless hash-based signatures. Choosing a well-studied permutation for these roles keeps the schemes' security assumptions narrow.

#Quantum impact

Like SHA-2, SHA-3 has no exponential quantum attack: Grover search yields only a quadratic speedup on preimages, and collision resistance follows the birthday bound. With sufficient output length it is considered post-quantum safe. SHA-3 differs from SHA-2 in construction, giving deployments a structurally independent alternative.