Extendable-output function
Extendable-output function (XOF) is an extension[1] of the cryptographic hash that allows its output to be arbitrarily long. In particular, the nature of the sponge construction makes any sponge hash a natural XOF (the regular hash functions with a fixed-size result are obtained from a sponge mechanism by stopping the squeezing phase after obtaining the fixed number of bits).[2]
The genesis of a XOF makes it collision, preimage and second-preimage resistant. Technically, any XOF can be turned into a cryptographic hash by truncating the result to a fixed length (in practice, hashes and XOFs are defined separately). The examples of XOF include the hashes from the Keccak family: SHAKE128, SHAKE256, and a variant with higher efficiency, KangarooTwelve.[1]
XOFs are used as key derivation functions, stream ciphers.[1]
References
- ^ a b c Peyrin & Wang 2020, p. 7.
- ^ Mittelbach & Fischlin 2021, p. 526.
Sources
- Mittelbach, Arno; Fischlin, Marc (2021). "Extendable Output Functions (XOFs)". The Theory of Hash Functions and Random Oracles: An Approach to Modern Cryptography. Information Security and Cryptography. Springer International Publishing. ISBN 978-3-030-63287-8. Retrieved 2023-06-22.
- Peyrin, Thomas; Wang, Haoyang (2020). "The MALICIOUS Framework: Embedding Backdoors into Tweakable Block Ciphers" (PDF). Advances in Cryptology – CRYPTO 2020. Cham: Springer International Publishing. doi:10.1007/978-3-030-56877-1_9. ISBN 978-3-030-56876-4. ISSN 0302-9743.
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