A way, esp. one of several possible variations, in which a set or number of things can be ordered or arranged.
Questions tagged [permutation]
194 questions
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What are the benefits of the two permutation tables in DES?
Why do we use a permutation table in the first step of DES algorithm and one at the end of the algorithm?
Am1rr3zA
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Is the inverse of a secure PRP also a secure PRP?
If a block cipher is a secure PRP, is its inverse a secure PRP as well? My intuition says yes but I'm not exactly sure.
On a related note, if a block cipher is a secure sPRP, is its inverse a secure sPRP?
I'm using the terminology "PRP = secure…
orlp
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Shannon confusion and diffusion concept
I read the document(not the whole document) from Shannon where he speaks about the concepts of confusion and diffusion. I read in many places(not in the document but around the internet) that confusion is enforced using substitution. Diffusion is…
BrunoMCBraga
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Are encryption algorithms with fixed-point free permutations inherently flawed?
Flaw in Enigma
One of the Enigma machine's flaw was the derangement (fixed-point free permutation) of the produced ciphertext, or simply put: No plaintext-letter can be enciphered to itself. See this example from Wikipedia of how this text (in…
AleksanderCH
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Replacing the Rijndael S-Box?
The Rijndael S-Box design generates a permutation cycle of type $2+27+59+81+87$. What effect would replacing that permutation with a cycle of type $256$ have on the security of AES?
bzc
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How to check whether the permutation is random or not
Imagine that my friend gives me the permutation $\pi$. He pretends that the permutation was generated completely random.
I'm suspicious and worried, because the permutation (for instance) looks like: $\pi(x) = ax + b \pmod n$ for some $a$, $b$. My…
Kirill Tsar.
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Why is AES not a Feistel cipher?
I am studying for an exam right now. And I wanted to make sure I got this point correct.
AES is not a Feistel cipher because the operations in AES are not invertible.
Is the above statement correct? If not, why isn't it a Feistel cipher?
mike
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Why is the permutation in AES (and other ciphers) not random or key-dependent?
If the permutation in AES (or other ciphers) were randomly generated or dependent on the key, would it not be stronger against differential attacks?
If this is so, then might we need fewer rounds for the same level of security?
Red Book 1
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Block cipher and parity of permutation
Can anyone explain the following text passage to me?
Most real-world block ciphers build even permutations,
because it's hard to build odd ones using small operations (32 bit)
on larger (128 bit) block size.
I don't understand the connection…
RomeoAndJuliet
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Shared secret: Generating Random Permutation
-- or: How to Play Poker Without a Dealer
I know this question is long but it's a really interesting theoretical problem about shared secrets and multi-party computation.
General Problem: "Shared Random Generation"
Consider the following scenario:…
leemes
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Santa Claus' secret permutation
This December, $N$ friends play secret santa: they select a random permutation $\sigma$ of $N$ (without fixed point). For Santa Claus, everyone has to bring a gift to the next person in the permutation. To preserve the magical spirit of the game,…
Steakfly
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Sponge with PRF instead of PRP
In most uses of Sponge mode of operations such as SHA3 and many of the round-2 candidates in the NIST lightweight cryptography project, the underlaying primitive is a cryptographic permutation - that is, it's bijective.
For reasons of curiosity, I…
DannyNiu
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What is the difference between a hash and a permutation?
As defined by Wikipedia a hash function is
[...] any algorithm or subroutine that maps large data sets of variable length to smaller data sets of a fixed length. For example, a person's name, having a variable length, could be hashed to a single…
rath
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Does there exist trapdoor permutation from lattices?
It seems that the lattice functions are either surjective (SIS) or injective (LWE), due to the error that is basically intended to destroy the structure and provide security. I was wondering whether there exist bijective functions for lattice, more…
user4936
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Proving RSA is a permutation
I am trying to prove that RSA is a permutation. All I can find is places where it is stated that it is a permutation because the function is bijective. I know that it is, but would like to see a detailed proof.
For clarity, we have $N = p \cdot q$,…
dtb93
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