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Questions tagged [compression-function]

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A compression function takes two fixed-size inputs: a chaining value and a message and returns a fixed-size value.

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I compared the various key schedules of AES, SHA2, BLAKE, Threefish and the approaches are very different. BLAKE and Threefish have the most basic key schedules (mere permutations/shuffles of words ...
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If they are invertible, why are they used? Is it just for bit diffusion and to increase the amount of correlation between the bits, and thus increase "confusion" in the internal state?
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I'm currently focusing on the implementation of Kyber (ML-KEM). I noticed that the avx2 version of the compress operation seems to use a fast division algorithm. ref version here: https://github.com/...
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I was reading CRYSTALS-Kyber design. They have used compress_q(x,d) to scale an element of $\mathbb{Z}_q$ to $[ 0,1,...,2^d-1 ]$. The definitions of ...
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I know that DES has 56 independent key bits, and that 3DES has 168 independent key bits by using 3 separate 56-bit DES keys. 3DES also has a block size of 64 bits. If I use 3DES as the underlying ...
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I'm designing a hash function which uses a double-tree construction and a compression function $c(s,A,B,C,a)$ ($s$ and $a$ may be omitted when there's only one of them) where $s$ is a set of three ...
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Rumba20 is a compression function that maps a 192-byte (1536-bit) string to a 64-byte (512-bit) string. It's designed to provide collision resistance by using Salsa20 (or ChaCha20) with the ...
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In this image, It describes the basic idea of an iterative hash function. I am confused as to why the i value is set to be m+t+1 ...
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I have seen multiple sources claim that the Merkle-Damgård transform is able to build a collision-resistant Hash-function $H$ for arbitrary-length inputs from a compression function $h : \{0,1\}^n \to ...
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In BLAKE2X paper it is said: BLAKE2X adds a constant overhead of $\lceil\ell/64\rceil$ (resp. $\lceil\ell/32\rceil$ compression function calls compared to the underlying 64-bit (resp. 32-bit) BLAKE2 ...
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I'm looking for a very fast function $f(m, k) $ that takes a 64-bit integer $m$ and a fixed secret key $k$ of virtually any size (generated by a CSPRNG) and turns them into a 64- or 32-bit integer $ r ...
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This is from Joan Daemen's Doctoral thesis Per page 64 (or PDF page 79) 4.7.1 Our approach Our goal is the design of simple and portable unkeyed and keyed cryptographic hash functions that are ...
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What is the differences between data compression as used in e.g. the ZIP protocol and compression as performed in cryptographic hashes? Are there common properties as well, apart from creating a ...
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Let's say I give you the sha256 hash of my password, which I'll call X. Now, the sha256 algorithm is a one-way function, meaning you can give it some input and get an output, but you can't get the ...
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In sha-256, when the words go through the compression function, they get added to the previous hash. In case of the first 64 rounds, they get added to the initial words ($\bmod 2^{32}$ of course). ...
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