Keccak is a cryptographic hash function that forms the basis of SHA-3, the newest member of the Secure Hash Algorithm (SHA) family.
Keccak was designed by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche, a team of European cryptographers (Daemen also co-designed the AES cipher).
Although Keccak can serve other purposes like data encryption, it is best known as a hash function. It produces the same output sizes as SHA-2 (224, 256, 384, and 512 bits), but its internal mechanism is quite different, which is why it is often described as a more modern alternative rather than just a more secure one.
Theoretical attacks against SHA-1 emerged in 2004 and 2005, raising concerns about its long-term reliability. SHA-2, designed by the US National Security Agency (NSA), had been published by NIST in 2001, but the migration from SHA-1 was slow.
By early 2017, major browsers and certificate authorities had largely completed the transition. In February 2017, researchers from Google and CWI Amsterdam announced SHAttered, the first practical collision attack (where an attacker finds two different inputs that trick a security system into generating the same hash) against SHA-1. Since then, SHA-1 has been considered unsafe for collision resistance, and the NIST announced plans to disallow SHA-1 for all applications by 2030.
NIST launched a public competition in 2007 to develop a new hash algorithm. At the time, no significant attack against SHA-2 had been demonstrated, but NIST wanted a successor ready before one appeared, since developing and standardizing a new function takes years. Keccak was submitted to the competition in 2008 by the four-member team, and in October 2012 NIST selected it as the winning algorithm. It was standardized as FIPS 202 (Federal Information Processing Standards) in 2015, officially joining the SHA family as SHA-3.
Looking ahead, SHA-3 adoption may grow as newer systems favor its different structure, though SHA-2 remains far from being successfully attacked.
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