NIST declares 'Keccak' SHA-3 winner after five-year competition

New security star

After a public competition lasting five years, NIST (National Institute of Standards and Technology) has chosen the wonderfully-named 'Keccak' to be the newest cornerstone of the global security architecture, the SHA-3 hash function.

Pronounced "catch-ack" (it makes sense if you say it aloud), the hash is the invention of a group of semiconductor boffins, Guido Bertoni, Joan Daemen and Gilles Van Assche of STMicroelectronics and Michal Peeters of NXP Semiconductors.

Although it probably won't reach widespread use for years, the SHA-3 (Secure Hash Algorithm -3) is important. It was invented to patch theoretical flaws in the current SHA-2 hash family used as a key authentication mechanism in digital signatures, and protocols such as SSL (and its successor TLS), SSH, and IPSec as well as in popular encryption-based programs such PGP and Skype.

NIST said Keccak had been chosen from 64 competition rivals because of its good performance in hardware - better than SHA-2 for a start - plus its ability to work across a range of devices of varying computing power.

Its inventors promoted Keccak on the basis of, among other qualities, its 'sponge' function, basically the mathematical design from which the hash is securely computed.

"Keccak has the added advantage of not being vulnerable in the same ways SHA-2 might be," said NIST expert, Tim Polk. "An attack that could work on SHA-2 most likely would not work on Keccak because the two algorithms are designed so differently."

But what is a hash function and what makes it different from encryption?

The easiest way of explaining this is to use a program such as Skype as an example. Skype encrypts the data it sends using AES; the hash (in fact one of a number of individual hashes within SHA-2) is used to ensure the secure communication of elements such as the user login without which the use of data encryption would be moot. This checking mechanism is utterly fundamental to Internet security.

SHA isn't overhauled very often for the obvious practical reason that it doesn't need to be until the established version has been shown to be insecure, or potentially insecure. When it is, it is announced well in advance of implementation.

Even security luminary Bruce Schneier declared himself happy with the result despite having submitted his 'Skein' as a rival option to Keccak.

"It's a fine choice. I'm glad that SHA-3 is nothing like the SHA-2 family; something completely different is good," he announced in his blog.

"Congratulations to the Keccak team. Congratulations - and thank you - to NIST for running a very professional, interesting, and enjoyable competition. The process has increased our understanding about the cryptanalysis of hash functions by a lot," he added.

"Keccak is a fine hash function; I have absolutely no reservations about its security."

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