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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Python code for linear and differential cryptanalysis
I want to find the minimum number of active Sboxes for AES circulant matrix circ(2,3,1,1) in Galois field GF(2^8) using pulp library from Python. Since I am a beginner, I am hoping if I can get the ...
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Would there be any advantage in combining Feistel network and substitution-permutation network in a single cipher?
One common way to design invertible block ciphers is using a Feistel network used in for example DES and Blowfish. Another common way is a substitution-permutation network used in for example Rijndael ...
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Heys Differential Cryptanalysis Question
I'm wondering if anyone is aware of the best input difference to input into the system Heys outlines in his paper (http://www.cs.bc.edu/~straubin/crypto2017/heys.pdf) to achieve a high probability ...
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Midori block cipher design: importance of $S_b$ as the S-box
With a use of almost MDS the Midori cipher provides a good diffusion. But why $S_b$ is used as S-box and what is its actual importance?
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Attacking a one-round SPN
From Introduction to Modern Cryptography, 6.2.1 Substitution-Permutation Networks
A description of an optimized attack on one round SPN
A better attack is possible by noting that individual bits of ...
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How round constants are chosen in a block cipher?
Block ciphers that are NOT LIGHTWEIGHT use relatively complex key scheduling algorithms to enhance their security and thwart some of the known cryptographic attacks. In such ciphers round constants ...
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16-bit entry in a S-Box of a SPN block cipher: Would it have the same speed/performance than a 8-bit entry?
I learned that in Substitution–permutation block ciphers, the maximum size of S-Box set to receive an entry from a data is the max numeric count of the data, for example, if the entry is 8-bits the S-...
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Is it possible to use words of bits as entries in S-Boxes bigger than 4/8 bits and achive similar security/speed in SPN block ciphers?
Blowfish splits a 32-bit word into 4 sets of 8-bits (1 byte) and use them as entries in its S-Boxes.
Kuznyechick splits two 64-bits words in many nibbles (4-bits chunks), use them as entries in its S-...
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In SPN block cipher, is each bit of the ciphertext dependent on each bit of the S-boxes set?
In substitution–permutation network block ciphers like AES, when encrypting a plaintext into a ciphertext, will each bit of the ciphertext be associated to each bit of the S-boxes set in the cipher?
I ...
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Connecting, joining or merging Substitution Permutation layer
I am trying to identify how the SP Network is constructed. I am looking for plausible solutions that help to connect these layers together and what are the ways that exist in literature other than Kam ...
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Substitution-Permutation Network (SPN) Example
I came in contact with an algorithm that deals with SPN in an example, first I'd like to give a definition of what it is:
Let $l, m, $ and $N$ be positive integers, let $\pi_s: \{0,1\}^l \to \{0,1\}^...
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What is the need of substitution and permutation networks in AES?
I have tried to answer this question for quite some time now. But a complete intuitive understanding still eludes me.
Consider an alternate construction for a block cipher without any substitution and ...
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Differential analysis of SPN
Reference : Tutorial by HM Heys
If we find a differential trail that holds with some non negligible probability for n-1 rounds for a n rounds SPN structure, then we can recover some of the bits of the ...
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ε-close to t-wise inependence of SPN (AES)
According to theorem 3.13, the 6 rounds of AES is 0.472-close to pairwise independence. It is also mentioned t-wise independence used to analyze higher order derivates attacks. it is also mentioned 3-...
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Construction of key recovery attack in O(2^(n/2))
I have to construct a key recovery attack on symmetric key encryption using a publicly known permutation $\Pi$ in $O(2^\frac{n}{2})$ time using $2^\frac{n}{2}$ queries to an encryption oracle.
The ...
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Can we design a block cipher based on SP-network without loss of E/D similarity theoretically?
I understand what SP-network (Substitution-Permutation Network) and Feistel Network look like. And those ciphers based on Feistel (e.g. DES) often achieve so called E/D similarity, which indicates ...
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Understanding Linear Cryptanalysis
I'm reading about the linear cryptanalysis of an SPN and I have some questions about the practicality of this. The example I'm looking at is from 3.3.3 of Stinson's Book and I believe the same example ...
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Definition Problem for toy SPN
I am reading Differential Attack from Stinson-Cryptography: Theory and Practice on a toy example of S-box(block Cipher) with Nr=n=m=4.
I am mainly confused in the following definition
Definition ...
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Is the order of applying transformations in SP cryptosystems significant?
SP-cryptosystems Is the order of applying transformations in SP cryptosystems matter? What will change if we first apply the P-transformation and then the S-transformation? Will cryptographic strength ...
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Design of SIMD-implemented cipher
Design of efficient of block ciphers needs consideration of many factors such as register size. i found that some ciphers can be SIMD implemented such as TWINE , SM4 , chacha20 ,SPIX ,and others.
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modified substitution permutation networks
I have a model of substitution permutation networks, modified as follows:
instead of iterating $n$ times a round(each of which is composed of the key mixing phase,
substitution S-BOX) and ...
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DES/AES invertibility
My professor has posted a couple of practice questions that so far I haven't been able to find the answer for and I was hoping you could help.
DES would remain invertible—it would still be ...
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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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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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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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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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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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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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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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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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Substitution-permutation network
Can anyone in 6th grade English explain the steps in the Substitution-permutation network algorithm or just point a link that does so? (which is included in many of the top modern algorithms)
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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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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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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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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. ...
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