# 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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### What are some design considerations for S-Boxes?

My studies in cryptography have been quite detailed so far, however, one area that hasn't been explained to me is how S-Boxes are typically designed. Typically, the S-boxes are provided "as is" by the ...
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### Calculate the Number of active s boxes

I really want to learn how to calculate the number of active s _boxes for block cipher cryptographic algorithms. I want to do that manually after running each round of an algorithm such as LED ...
331 views

### Number of active s boxes

How can I calculate the minimum number of active s_boxes for block cipher algorithms such as present algorithm? I have read in that, but I couldn't understand the meaning of branch number.
332 views

### Simplified AES S-box multiplication - calculation error

I have a problem to calculate the S-box in S-AES. The affine transformation is defined: I read that it is a normal matrix multiplication. I chose the bits $0101$ and built the inverse $1011$. $b_0$ ...
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### How many primitive cryptography operations are there? [closed]

Every cipher I've encountered seems to be built from slight variations of only three basic operations: the S-box, the P-box, and the XOR. I’m just wondering, are there any others? And if there aren'...
313 views

### AES and GOST 28147-89 “Magma” Comparison

I am trying to understand how AES is comparable to GOST 28147-89 "Magma". Like for parameters such as bit shifting and addition of the subkey to the input, which are a part of Magma, what is their ...
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### Finding output given an S-box input of 8 bits

I'm given the following table: I'm told to find the output given an hexidecmal input of 2B. I know that 2B in binary = 001 01 011 So I took the first two and ...
355 views

### Security Implications of Fixed & Opposite Fixed Points of Sbox

Fixed point means when Sbox Input is equal to Sbox Output whereas Opposite Fixed Point means when Sbox Input is complement of Sbox Output. How does Fixed and Opposite Fixed Point affect the strength/ ...
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### Measure Strength of Mix Mode Modular Arithmetic based Confusion Layer

Strength of sboxes is generally measured by different properties eg non linearity, fixed points etc. If confusion is provided by Mixed Mode Modular Arithmetic (eg as in IDEA), how to measure the ...
419 views

### Does the DES s-box only provide confusion, or does it also provide an avalanche effect?

In DES, does the s-box provide an avalanche effect or does it only provide confusion in the ciphertext?
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### Security of the AES with a Secret S-box

In this paper they change the $AES$ S-box to a uniformly random one and answer the questions: How does the security of AES change when the S-box is changed by a secret S-box? Would it be safe to ...
175 views

### Non Linearity of huge Sbox

Sboxes provide confusion in cipher. Non Linearity measures the strength of sbox layer. In order to measure non linearity of sbox, a table is computed to measure distances with its affine functions. If ...
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### AES S-box calculation

I am trying to design the s-box for AES. Quoting from Wikipedia, the algorithm for applying affine transformation in AES s-box calculation is ...
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### Number of Substitution boxes

How many possible 16 bit S-boxes exist? (AES uses 8 bit substitution boxes) I first taught of calculating 128(keysize in bits)/8(bits) =16, but I believe it's wrong.
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### How can AES-like block cipher without non-linear component be broken?

I am taking a course on block ciphers and recently I have faced up with such an exercise: if an original AES's highly non-linear Sbox is replaced by a linear substitution (see example below), how one ...
671 views

### How can one construct the weakest S-box ever?

Is it possible to come up with an NxN S-box which would have a difference distribution table with N entries of 100% probability? I am studying the properties of S-boxes and I don't quite understand ...
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### Why do we keep designing new static s boxes?

As I understand s box properties, they primarily need high non linearity and low auto correlation. But most importantly for this question, they're not secret. There are many questions on this site ...
106 views

### Can a stream cipher with a big S-box create ASIC-resistance?

For a proof of work system a hash algorithm generates one pseudorandom index each round, in the same manner as RC4 and Spritz do. And it uses a bigger S-box, e.g. 2^20 numbers. The actual hash would ...
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### S-box basic question

I'm trying to understand DES and a bunch of other cryptographic systems using S-Boxes. I have now a quite basic question about how Sboxes work in general. For DES, Sboxes are substituting a 6-bits ...
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### How many Affine function can be made from $4 \times 4$ and $8 \times 8$ S-boxes?

The nonlinearity of an S-Box is defined as the non-linearity of its vectorial Boolean Function. Let $F$ be the hamming distance between the set of all non-constant linear combinations of component ...
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