Questions tagged [s-boxes]

(or substitution boxes), components in many block ciphers used to substitute parts of the data in a non-linear way. While often fixed by the algorithm (like in DES and AES), sometimes they are key-dependent (like in Blowfish).

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102 views

How to calculate the Inverse of random AES S-BOX (asuming we don't know how the S-BOX built)?

I'm recently studying cryptography, and I have a task for collecting the s-boxes for AES, and then implementing that s-boxes for encrypting & decrypting, but most of the S-boxes I found are not ...
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36 views

Statistical Cryptanalysis. Would one "reverse" weak key schedule algorithms or peel off each one of internal rounds?

The context is iterated ciphers. Regarding Differential and Linear Cryptanalysis, the methods seem to make a cryptanalyst able to do an educated guess on a partial subkey (e.g. bits from the last ...
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28 views

Shark cipher SBox

In the literature, I can’t find the S-Box component of SHARK block cipher. I appreciate if anyone help to find the elements of the S-Box of this cipher.
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72 views

Construction of S-Box in PRESENT

I'm currently working on an hardware implementation (with verilog) of PRESENT-80 for research purposes. Due to our goal to strengthen the security of PRESENT-80 with Masking and Error Detection I need ...
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32 views

Calculate number of active S-boxes for a cipher where one word observes multiple times overlapped S-box substitution in a single encryption round

There are many ways in which the number of active sboxes of a cipher for one round can be calculated. Like, a manual approach (all possible input differential are applied in the two plaintexts $P_0, ...
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115 views

Why key reuse is not an issue in a Feistel cipher?

I have a good understanding of stream ciphers and one time pad. I also know the dangers of using the same key in a PRG for a stream cipher. However as far as I can tell, the Feistel block cipher uses ...
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45 views

Implementing the sbox components using lookup tables

Does it is possible to implement the components of a SBOX tables using lookup_tables. For example for a 4-bit SBOX it is possible to obtain the component 3 using SAGE in the following way ...
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58 views

Algebraic Normal Form of a function in $\operatorname{GF}(2^{n})$

Consider the function $f(x)=x^{2k+1}$ in $\operatorname{GF}(2^{n})$ for $n$ odd and $\gcd(k,n)=1$, which is differentially 2-uniform function. For $n=3$, $k=1$, I want to find the Algebraic Normal ...
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51 views

LAT of sboxes, sum of coloms and rows

let we have sbox s: Vn -> Vn. If we make LAT table for s, fix any row and get a sum by columns, that sum would be $+-2^{n-1}$. And vice versa, if we fix any column and get a sum by rows, that sum ...
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Why is it not possible to attack an AES by creating a function to model the substitution that occurs in a s-box?

I realise that s boxes are able to make the transformations done in AES non-linear. However I am unsure how this makes AES secure. For instance if we had no s box then it is possible to calculate the ...
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How to use sagemath to find nonlinear invariants of S-box?

I read a paper about a nonlinear invariant attack that is "Nonlinear Invariant Attack: Practical Attack on Full SCREAM, iSCREAM, and Midori64" And I've found a website of sagemath : https://...
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Non-linear phase that's Side channel attack proof

I'm designing a cipher and I'm looking for a Non-linear phase in my cipher that is side channel attack proof, I know that Sboxes are vulnerable to to that because of accessing the cache. I'm thinking ...
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43 views

Quadratic Equations to Describe SBox

I am using a 8 bit Sbox having 16 entries with a lookup table of 4x4 in cryptographic algorithm. Sbox is constructed on subgroup of galois field 2^8. I want to calculate number of quadratic equations ...
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535 views

What is this AES SBOX triplet property?

While playing around with the AES SBOX, I found out that there are 85 unordered triplets (a, b, c) that have the following characteristics: ...
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39 views

nonlinearity and autocorrelation of common s-boxes

I cannot find publications comparing the properties of popular cipher s-boxes. First of all, I am interested in nonlinearity and autocorrelation of s-boxes, which are used in seed, cast-128, camellia ...
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22 views

Conditional probability being Constant in Threshold Cryptography

I am working on Threshold implementation of algorithms to prevent side channel attacks. I am not that much proficient in Statistics and Probability theory. I want to know what is the significance of ...
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138 views

Division property table of SBox

In Table 12 (page 23) of the GIFT paper, the "Division property" table is given. I could not understand how it has been computed. My questions: May I have an algorithm on how to compute the ...
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1answer
92 views

Building a 4-bit S-box with a 4-uniform DDT

I am looking for a 4-bit S-box which has only 4s in its difference distribution table (except the top left corner) but I was not able to find one in the literature. Has such an S-box been already ...
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51 views

SHA3_512 as dynamic SBOX generator

I'm creating a substitution-permutation cipher (for learning purposes only of course) and I'd like to implement dynamic SBOXs. The cipher will have a block size of 128, and 32 rounds. These SBOXs will ...
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47 views

What does "the input difference of each Sbox should be zero" mean?

While going through the article, The MALICIOUS Framework: Embedding Backdoors into Tweakable Block Ciphers. I came across this statement in order to have a deterministic differential characteristic ...
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1answer
72 views

AES with other SBoxes

I'm not a cryptologist, just an interested engineer (& now retired). I used to design hardware with AES en/decryption blocks & generate test vectors using my own Tcl script using the embedded ...
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163 views

Why is the nonlinearity of this Boolean function evaluating to $\frac12$?

I am using the method presented in this paper to find the nonlinearity of the function $$ f: \mathbb{F}^1_2 \to \mathbb{F}^1_2 \\ f(x) = x$$ The truth table is $f = [0 \space \space 1]$. Now, I read ...
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167 views

Differential and Linear Cryptanalysis on Random Sbox

Assume that we use the key to perform a uniform permutation to generate a sbox. The literature is rich supporting the statement that a random Sbox can make any cryptographic scheme weaker. I have ...
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1answer
65 views

Is it possible to use an S-box similar to the one used in DES in AES? How would this work?

I'm reviewing some questions given to me by a professor and am stumped on this one. My initial guess is that yes, this is possible, but I do not know how to explain it, specifically for a function $\{...
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67 views

Problems on ANF equation?

I tried to solve SBox as given in this link I am trying to understand this paper SBox. In this on page no.4 the correct equation of given SBox is mentioned. I am not getting how to design ANF equation ...
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362 views

AES-CTR security if S-boxes substituion is omitted?

I understand why s-boxes are needed in general especially when ECB mode is used(because of using the same key for encryption of other blocks)but I wonder if it's ...
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Generate ANF equation? [duplicate]

Given an SBox, how can I generate its component equations (in ANF)? given in this link: https://en.wikipedia.org/wiki/Algebraic_normal_form For example, let's say I have this SBox: $$\{1, a, 4, c ,6 ,...
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87 views

LAT of an SBox, values are even

This is probably a silly question, but I could not find any reference. For the DDT of an SBox, it is easy to see why all the values are even. Is there any related result for LAT (i.e., all its values ...
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How to implement arbitrary s-box in a side-channel-free way in C?

This could be a question for CodeReview.SE, but I thought it might require non-trivial cryptographic knowledge to merit it on-topic here. The C language is chosen as it's a common language for ...
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243 views

Is AES S-Box resistant to side-channel attacks?

I know that implemntations with T-tables such as Golang's are prone to side-channel attacks, but is AES's S-Box wihtout any additional table also insecure ?
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Is ShiftRows(SubtBytes(x)) = SubtBytes(ShiftRows(x)) the same for the same entry : in AES

Is ShiftRows(SubtBytes(x)) = SubtBytes(ShiftRows(x)) the same for the same entry : in AES It seems like these two are equal, can someone explain in theoretically?
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160 views

Cryptanalysis of a feedback shift reigister with an S-box

I’m just getting started on learning cryptography and here is a problem from exercises about which I'm totally confused: This is a 32-bit feedback shift register to encrypt some message. The register ...
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64 views

S-box for byte substitution where the s-box values are multiplicative inverses of 257

The title basically says it. We have a 16 by 16 s-box, $256$ entries total. And the first value is the multiplicative inverse of $257$, so $1 \times k \bmod 257, \space k = 1$. $2 \times k \bmod ...
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87 views

What are the standard properties of an S-Box [duplicate]

Apart form the following, what are the other properties of a good cryptographic Substitution box or the S-Box: Changing one input bit should change about half of the output bits. Each output bit ...
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37 views

AES S_BOX Generator additive constants

I try to generate other S_BOX for AES but I don't realize how to choose additive constants for S_BOX from decryption if for encryption it is 0x63 why is ...
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1answer
155 views

Inversion in $GF(2^{10})$ Using Composite Fields

I'm designing a circuit that uses many $GF(2^{10})$ inverters. Normally for this sort of thing I use lookup tables. (Itoh-Tsujii is not efficient for these smaller fields.) This application is for ...
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1answer
95 views

How to generate a 16 X 8 perfectly nonlinear S-box

I want to generate a 16,8 perfectly nonlinear S-box for an encryption algorithm I am working on. I don't have a background in math, and I'm an undergrad, so a lot of the math involved is very ...
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what if the S-boxes in DES were "optimal"

if we assume that the s-boxes in DES were optimal. that is for each s-box, every cell in the DDT equals to 4. is there a differential characteristic in a good probability?
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67 views

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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141 views

Would using perfect S-boxes in F function of an unbalanced Feistel network produce a simple and secure cipher?

When I read some articles about cryptography on wikipedia, I took note of the following statements (please, correct me, if any of these are wrong): Perfect S-box (based on bent functions) provides ...
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85 views

Side-channel vulnerability of AEGIS naive AES implementation

AEGIS, one of the finalists of CAESAR competition, uses a naive implementation of AES encryption round as its reference implementation. By naive I mean it uses secret dependent table lookups, so it is ...
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Do the keys in AES determine the S and P boxes? [closed]

I once read somewhere that the keys determine the S and P boxes. If so, how does that work?
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90 views

A bit-sliced implementation (or the algebraic normal form) of the two FIDES S-Boxes

I want to see a bit-sliced implementation of 5-bit and 6-bit S-Boxes of FIDES or, at least, a representation of these two functions in algebraic normal form. Where can I find it?
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168 views

Can I change the S-box and P-box in DES?

I am a newbie to crypto and just one quick question on the s-box and p-box of DES. I understood that the s-box is where the security comes from and NSA has somehow decided how it should be filled in. ...
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How TAU function of SM4ni cipher is implemented?

I am trying to understand the SIMD implementation of TAU function of SM4 which is as follows: ...
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448 views

Is the following s-box more linear or more non-linear?

I am trying to figure out whether the following simple s-box configuration I created is more linear than non-linear or vice versa more non-linear than linear? The parameters for this 16*4 table of ...
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698 views

how can I test quality of sbox?

I have 11 sboxes, I want to test them and find the best one. How can I do that, I found several criterions for that but I could not understand.
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how to compute Bit Independence criterion of SBOX?

I want to compute BIC's of my Sboxes, I found out some theses for that but I could not understand how to do it. Can someone help me?
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129 views

$\alpha^{2^{m} + 1}$ is a generator of $\operatorname{GF}(2^m)$?

This is from a paper (Partitions in the S-Box of Streebog and Kuznyechik) about S-Boxes: Let $\operatorname{GF}(2^{2m}) = \mathbb{F}_2[X]/p(X)$ be a finite field of even degree defined by a primitive ...
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DES - Weakness in Sbox

In the book "Introduction to Cryptography with Coding Theory ", in the chapter about the Differential Cryptanalysis for Four Rounds for DES algorithm, the authors say: There is a weakness in the ...

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