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Questions tagged [spn]

A Substitution-Permutation-Network is a structure that has been used to create a number of different block ciphers (e.g., AES, Picollo, Present...)

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Can the S-Boxes and the P-Box commute?

Consider an SPN operating on blocks of size $m\ell$ bits. Suppose that each round consists of adding the round key (bitwise xor), applying $m$ S-boxes (so that each S-box operates on $\ell$ bits), and ...
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1answer
1k views

Linear Approximation Table of S-Box for SPN

I havejust gotten to Linear Cryptanalysis and I'm studying some material on Linear Attack's against SPN. I see here http://www.cs.bc.edu/~straubin/crypto2017/heys.pdf on page 11 that they calculate ...
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Classify a (block) cipher

Can someone help me to classify a cipher algorithm? It's: a block cipher (1 block = 6 bit); a hashing algorithm (i.e. data is ...
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59 views

Determining number of required plaintext pairs for differential cryptanalysis

When carrying differential analysis of a SPN network, how can one determine the number of required plaintext for the attack to be successful with high probability?
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3answers
403 views

Substitution-permutation network visualizer

I'm doing differential analysis of a toy block cipher in which I've to extract the differential characteristic of the first n-1 rounds. However, I can't do that very well as I can't see the network ...
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1answer
92 views

What does this notation means $\mathbb{F}_{2^{-}}$?

I have seen various papers to use this notation $\mathbb{F}_{2^{-}}$ to describe the diffusion layer. As for example the permutation in AES (MixColumns). So, we have a field with order of 2, what does ...
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258 views

Alternatives to sbox's for diffusion?

Are there any other alternatives to Sbox's or SP networks to provide diffusion preferably more basic alternatives which still provide a good degree of security?
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1answer
420 views

substitution-permutation network construction

I want to understand more about substitution-permutation network, if we modify it instead of carrying out the key-mixing, substitution, and permutation steps in alternating order for r rounds, the ...
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1answer
106 views

Using a round function intended for an SP network in a Feistel network?

If I use the round function from a secure SP network (such as AES) and use it in a Feistel netwok, is this a good starting point for the second cipher? My thought is "yes" because: it already has ...
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1answer
2k views

What is the diffrence between Feistel networks and SPN?

I recently read about the concept of Feistel Networks and Substitution Permutation Networks but what is exactly the difference between the two ?
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1answer
274 views

Question about the security of Substitution-Permutation Network

In general, we execute key-mixing, substitution and permutation sequentially in a single round in a n-round SPN, but if we execute n-round key-mixing firstly, n-round substitution secondly and n-round ...
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2answers
572 views

What is the intuition behind AES or SPN?

I'm new to cryptography and have just encountered AES and SPN. I would like to know how the S-box, permutation step and the MixColumn step help improve security. It seems to me (perhaps mistakenly) ...
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12k views

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?...
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644 views

Increase number of rounds for SPN and Feistel ciphers

Read a post on Schneiers blog (and again 2011) about increasing the number of rounds for AES from to "AES-128 at 16 rounds, AES-192 at 20 rounds, and AES-256 at 28 rounds" to raise the security. ...