# Tagged Questions

Linear cryptanalysis is a known plaintext attack and uses a linear approximation to describe the behavior of the block cipher. Given sufficient pairs of plaintext and corresponding ciphertext, bits of information about the key can be obtained and increased amounts of data will usually give a higher ...

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### A5/2: Ciphertext Only Attack

A5/2 could be attacked with cipher-text only, using the Error Correction Code, in order to retrieve the session key. For the purpose of simplicity suppose that the error correction code copy the ...
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### linear cryptanalysis: how are the subkey bits removed from the linear approximation?

I'm currently reading the tutorial on linear/differential crypta here: https://www.engr.mun.ca/~howard/PAPERS/ldc_tutorial.pdf End of page 14/Beginning of page 15: all the bits from the subkeys are ...
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### Last Sbox of a block cipher for Linear Cryptanalysis

I figured I should try to learn about linear cryptanalysis with a super simple cipher with only one Sbox. The problem is that with that approach the last subkey bits seem to be involved in the linear ...
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### Differential & linear characteristics for integer multiplication

What are the probabilities of differential & linear characteristics for the function that XORs the high and low bits from a $n \times n \rightarrow 2n$ bit multiplication? I remember reading ...
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### Extracting key bits from linear cryptanalysis equation for SDES

From the linear cryptanalysis of SDES, we get a linear equation consisting the K[1, 3] of the round key 1 and 2. From this how will I retrieve the key bit? How do we solve the linear equation we get ...
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### How does non-linearity (S-box) add security to AES?

I'm trying to understand how AES guarentees security. One of the named points on the web is that AES uses a non-linear step (the SubBytes step). But how exactly does the Rijndael key schedule add ...
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### Linear cryptanalysis complete key guessing

In linear crypt analysis, partial sub keys are guessed and verified for its correctness with the help of plaintext and ciphertext. From the partial sub key, how it is possible to guess the complete ...
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### Breaking linear blockcipher - expanding recursive formula

I am trying to break a block cipher that can be defined as follows: We have 12 rounds and at each round we perform the following operation. We split 64 bit data into 2 parts each 32-bits, $\ x_r$ ...
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### Differential bound of the S-Box in GOST R34.11-2012

In Russian GOST R34.11-2012 LPS-transformation is used. LPS gets all of its non-linearity from the 8-bit S-box S, which apparently has been designed to offer resistance against classical methods of ...
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### Why is not there any ideal S-Box?

i read about linear cryptanalysis and about S-Box that there is not any ideal S-Box (ideal S-Box is a random S-Box in another words S-Box that bias of input and output bits is zero) then i read about ...
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### Difference between linear cryptanalysis and differential cryptanalysis

What is the main difference between linear cryptanalysis and differential cryptanalysis? For example in relation to DES?
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### Combining LFSRs for Stream Ciphers: Why do we need high non-linearity?

Linear Feedback Shift Registers (LFSRs) can be excellent (efficient, fast, and with good statistial properties) pseudo-random generators. Many stream ciphers are based on LFSRs and one of the possible ...