Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [keccak]

SHA-3, originally known as Keccak, is a cryptographic hash function designed by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche.

SHA-3, originally known as Keccak, is a cryptographic hash function designed by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche. SHA-3 uses the sponge construction in which message blocks are XORed into the initial bits of the state, which is then invertibly permuted. In the version used in SHA-3, the state consists of a 5×5 array of 64-bit words, 1600 bits total.

104 questions
6
votes
1 answer

What is the size of codomain of a function $G(x) = F^A(x) \oplus F^B(x)$, where $F(x) = \text{Keccak-}f[1600](x)$?

Assuming that $m$ is a multiset of bitstrings where all bitstrings have the same length, let $D(m)$ denote the number of distinct elements in $m$. That is, $D(m)$ is equal to the dimension of $m$. For example, if $$m = \{00, 10, 11, 10, 11\},$$ then…
lyrically wicked
  • 1,337
  • 7
  • 10
6
votes
0 answers

Why is Keccak-f reversible?

It seems like the Keccak permutation is reversible, which is not making the output of SHAKE forward-secure. In the sense that if one state is leaked, everything can be recovered. I wanted to know the reason why the permutation was not one-way. Or…
David 天宇 Wong
  • 1,535
  • 11
  • 26
4
votes
1 answer

Is it reasonable to assume that $\text{Keccak-}f[25n]$ block permutation is defined for any value of $n$?

Wikipedia contains the following claim for $\text{Keccak-}f[25w]$: It is defined for any power-of-two word size, $w = 2^ℓ$ bits. Although all official descriptions of Keccak do not explicitly mention well-definedness of $\text{Keccak-}f[25n]$…
lyrically wicked
  • 1,337
  • 7
  • 10
3
votes
0 answers

Small(er)-lane Keccak-f: impact and usage

Keccak defines a family of hash functions, by building a sponge out of a permutation Keccak-$f[b]: \{0,1\}^b \rightarrow \{0,1\}^b$. This permutation function is parametrised using $b$, which is the string length of the permuted…
Ruben De Smet
  • 2,370
  • 11
  • 26
3
votes
2 answers

What are the values of $w$ such that the corresponding $\text{Keccak-}f[25w]$ function is invertible (bijective)?

From this answer, I see that from a mathematical point of view, one could define the $\text{Keccak-}f[25w]$ permutation for an arbitrary value of $w$. I am interested in the following question: disregarding all properties of the resulting function…
lyrically wicked
  • 1,337
  • 7
  • 10
1
vote
1 answer

shake-128 in 32-bits platform

I am implementing shake in 32-bits microcontroller, so I would like to use bit interleaving. I checked the code in: https://github.com/floodyberry/supercop/blob/master/crypto_hash/keccak/simple32bi/Keccak-simple32BI.c but I do not understand how is…
Andreas
  • 13
  • 3
0
votes
2 answers

What is a permutation in Keccak?

I am trying to understand Ethereum's hash algorithm Keccak. Keccak uses permutations in the hashing process. Could anyone explain me what this permutation looks like or how it works ? I only know permutation from mathematics, is it the same here? A…
Blnpwr
  • 103
  • 3