# 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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### AES vs Kuznechik (GOST R 34.12-2015) comparsion [closed]

Which algorithm is more crypto-resistant: AES or Kuznechik (GOST R 34.12-2015)?
• 109
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### Non-Linearity of an S-Box [duplicate]

This should be pretty simple question I presume. So let's say I have an 8x8 S-Box. I can easily treat it as 8 different boolean functions for each of the 8 input bits. Is the non-linearity the lowest ...
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### Can a byte/word inserted as an entry in a Feistel S-box be breakable?

Let's suppose I insert these two 4-byte words (32-bits) in a feistel S-box with 1024-bytes of size (256*32-bits), (like Blowfish does): blah bleh What kind of attacks could possible be made to ...
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### How to caculate the inverse of function $x^3$ in $\mathbb{F}_{2^n}$

How to caculate the inverse of function $x^3$ in $\mathbb{F}_{2^n}$?, Any monomial $x^d$ is a permutation in the field $\mathbb{F}_{2^n}$ iff $gdc(d,2^{n}-1)=1$,why?
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### How to calculate the inversion fuction S:S:\mathbb{F}_{2^n}\rightarrow \mathbb{F}_{2^n},with S(x)=x^{-1}

The S-box is defined as the generalised inverse function $S:\mathbb{F}_{2^n}\rightarrow \mathbb{F}_{2^n}$,in quotient ring $\mathcal{R}:=\mathbb{F}_{2^n}[X]/(X^{2^n}-X)$ with $S(x)=x^{-1}$, is ...
1 vote
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### 99 in AES s-box, where it came from? [duplicate]

The multiplicative inverse in AES s-box is transformed using the following affine transformation: $s = b \oplus (b \lll 1) \oplus (b \lll 2) \oplus (b \lll 3) \oplus (b \lll 4) \oplus 99_{10}$ Where ...
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### DES SBOX Output with Bitslice

I am not understanding how to compute the output bits of a 6-to-4-SBOX with bitslice technique in DES. Matthew Kwan made a brief recap in his paper "Reducing the Gate Count of Bitslice DES" ...
1 vote
199 views

### How to solve this S Box?

I have performed the XOR and the result comes as 1001. Now my confusion is that in standard S-Box (DES) the input is 6 bit where the first and last bit together specifies row and 4-middle bits column. ...
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### What is the time and space complexity of the AES S-boxes? [closed]

What are the time and space complexity of the AES S-boxes? Could someone please explain how these are determined?
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### How is the polynomial multiplicative inverse calculated here? [duplicate]

How is the multiplicative inverse calculated in the following? Please explain with details. Note: I understood how polynomial value 283 is calculated.
1 vote
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### How does this code calculating AES S-Box work?

How does this code calculating the AES S-Box work? I don't understand the overall calculation procedure. Code is attached below: ...
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### 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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1 vote
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### 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 ...
1 vote
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### 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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### 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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### 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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### 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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1 vote
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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 ,...
112 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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1 vote