(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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Evaluating Algebraic Complexity of a S-box

While studying the design and the desirable properties of an AES S-box , I came to know that Algebraic Complexity is also an important property of an S-box which is usually considered while evaluating ...
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How can I design a cryptographically secure, key-dependent s-box?

I would like to design a cryptographically secure, key-dependent s-box, but I am not sure how. Mainly, because I am unsure about the difference in design compared to a random s-box. What is the ...
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How to calculate the non-linearity of an s-box?

I am struggling to understand how to calculate non-linearty of an s-box, could someone show me a detailed example? I found “How to calculate non linearity of AES S-box?” which helped a little, but I ...
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CAST-256 (CAST6) versions or S-Boxes

Are there different versions of CAST-256 - also known as CAST6 - available? Are there different S-Boxes available for CAST-256? If there are different versions or S-Boxes what identifier should I use ...
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About the Algebraic Normal Form (ANF) of S-Box in DES

I've thought up a way to represent the transformation of S-Box in DES by ANF. Let $x_i\;(1\le i\le 6)$ be the input of an S-Box, $y_i\;(1\le i\le 4)$ be the output, for example, then $$y_1= 1\oplus ...
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DES S-Box properties

Two of the properties that lead to the design of DES S-Boxes are: 1)For any non-zero 6-bit difference between inputs, no more than 8 of the 32 pairs of inputs exhibiting that difference may result ...
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S-Boxes and SP-Network

I work on an exercise and I have to study functions as : $ f : \mathbb{F}_q \rightarrow \mathbb{F}_q$ with $q = 2^n$ which can define a S-Box for SP-Networks. There is a question that I can't answer ...