SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions
The SHA-3 standard does not differ markedly from the draft version that was released for public comment in May 2014. It specifies a family of functions based on Keccak, the winning algorithm selected from NISTs SHA-3 Cryptographic Hash Algorithm Competition.
SHA-3 is not the only family of hash functions that NIST approves for hashing electronic messages; the SHA-2 family, specified in FIPS 180-4 that NIST approved for use in 2002, remains secure and viable.
SHA-3 is very different from SHA-2 in design, says NISTs Shu-jen Chang. It doesnt replace SHA-2, which has not shown any problem, but offers a backup. It takes years to develop a new standard, and we wanted to be prepared in case problems do occur.