Questions tagged [permutation]
A way, esp. one of several possible variations, in which a set or number of things can be ordered or arranged.
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Combining an LFSR with a permutation
LFSRs of length $L$, by themselves, are considered insecure because their state can be recovered with at $2 \times L$ bits. However, LFSRs are still get attention in cryptographic designs because they ...
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What are the security implications of having inverse_sbox -> XOR tweak -> forward_sbox?
I have an application in mind that requires only the 32-bit sub-permutation from AES [x86; AESENC] (but skip shift rows step) but it turns out that the transposition step to undo shift rows (x86; ...
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ARX vs. AR when performance of XOR = ADD = 1 cycle
ARX ciphers are in large part implemented for the benefit of software & modern CPU's.
Literature also suggests that AR ciphers are not as efficient as ARX when it comes to gate count - efficiency ...
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Is a secure 8-bit cipher possible?
Firstly, a sanity check: $\log_2((2^8)!) = 1684.$
There are $2^{1684}$ possible $\{0,1\}^8 \rightarrow \{0,1\}^8$ permutations.
However a fixed permutation would be highly vulnerable to known-...
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Why do popular ARX ciphers have large states?
salsa20/chacha20/blake/blake2/blake3 all utilize a 4x4 grid of words on which transformations occur row-wise and then column/diagonal-wise.
State size varies between 512 and 1024 bits based on word ...
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Order of Enigma's rotors does not increase total number of keys
I have a question about “order of rotors”. I read about Enigma but I do not understand this point. If the machine has 3 rotors, for example 1_2_3, so it has 26×26×26 total keys. If we change the ...
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I just want a post-quantum permutation and I don't care about efficiency. Can multivariate reciprocals help me?
Let's say there's an application that require a public-key permutation, and we can throw all other requirements away, and design one out of reciprocal multivariate system. Is this viable? If yes, how ...
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What are advantages/disadvantages of an invertible tweak schedule in a tweakable block cipher?
I have been doing research on a tweakable block cipher called BipBip. This is a rather niche cipher so I'll give a few facts about it for background before asking my question:
The structure is based ...
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I'm curious on what the downsides of the public-key encryption method from my research project could be
As part of my final BS degree research project, I had to work with an encryption method based on research done in my university. What surprised me, is that while the method is very simple, I can't ...
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How to attack the shuffling of correlated numbers?
Suppose I have a function that accepts vector input $x$ and outputs vector $y=f(x)$. I want to protect the output $y$ through shuffling numbers in it. I hope the shuffling can confuse the attacker by ...
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Inverse Permutation in Sequential Manner Per-XOR (𝑃𝑥−1)
I'm trying to understand a protocol proposed in a research paper. There is a step that involves computing inverse Per-XOR. The explanation along with solved example is given below:
"Perform ...
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Per-XOR computation
I have an assignment where I have to understand a protocol proposed in a research paper. The first step involves computing Per-XOR, but I can't seem to understand the explanation given. Below is the ...
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Rationale for BLAKE2 message schedule?
BLAKE2 uses a message schedule I did not see before. It uses permutations of pieces of the message block.
The BLAKE2 book did not state the rationale for such a choice and how it contrasts with the ...
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Impossibility of uniform generation in random world
I was reading Limits on the provable consequences of one way permutations by Impagliazzo and Rudich when I got stuck on a sentence.
First of all, they define a polynomial relation that is any relation ...
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What is the inverse of this variant of the Gimli SP-box?
Consider a slightly modified variant of the Gimli SP-box:
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