# Tag Info

Accepted

• 23.1k
Accepted

### How to convert a Galois LFSR to a Fibonacci LFSR?

In this answer I will consider the Galois LFSR mentionned at this question: Sequence output by a Galois type LFSR see the image below. First we assume that the 5 positions of bits are numbered from ...
• 10k
Accepted

### Sequence output by a Galois type LFSR

You made a mistake in the propagation of the feedback. If you follow the LFSR very slowly this is what you get: ...
• 10k

### How to design a balanced LFSR with period 1023 and linear span 55?

The polynomial factorisation of $X^{2^L-1}+1$ into irreducible factors gives you all the polynomials $g_i(X)$ that can be used as LFSR polynomials in generating any sequence of period $2^L-1.$ Say ...
• 23.1k
Accepted

### Period, correlation and auto-correlation of non-linear feedback shift registers based sequences

The reason such generators are used is to avoid the Berlekamp Massey attack by introducing high linear complexity. However, even though there are many publications on these, the theory is far from ...
• 23.1k

### Is it possible to crack a LFSR encrypted file without using bruteforce?

First up: a 5 bit LFSR is horribly small, so getting the initial seed which was used is a piece of cake. But indeed, it’ll basically boil down to a (rather quick) brute-force job where – unless that ...
• 18k
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### Decrypting Ciphertext with partial Key Fragment using LFSR and Berlekamp-Massey

TL;DR: If you have a similar question, then use the online Berlakamp-Massey algorithm to get the minimal polynomial by providing the given keystream, then get the C++ code from github and then replace ...
• 49.2k

### Why are stream ciphers based on linear-feedback shift registers so popular?

A complement to @kelalaka's excellent answer. Here are a few LFSR (and NLFSR for Trivium) based stream ciphers that have not been broken. Trivium Self shrinking generator. Also, some stream ...
• 23.1k
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### Explanation of $z^{-1}$ and $T_{1,2}$ within E0 Bluetooth encryption algorithm

This article Cryptanalysis of the Bluetooth Stream Cipher by Canniere et al. explains in details; \begin{align} T_1 : \mathbb Z^2_2 &\mapsto \mathbb Z^2_2\\ (x_1, x_0) &\to (x_1, x_0)\\ \end{...
• 49.2k

### Multiplication of two LFSR

TL;DR: It's complicated. Intuitively, the idea that all roots of the two polynomials contribute to the linear complexity of the product sequence, which can sometimes result in very high linear ...
• 23.1k
Accepted

### What is the result of not connecting the 1st register to the xor gate in LFSR?

OK, it is a question of what the connection polynomial is, the figure helps clarify what you are doing. In both cases the polynomial is degree 8. Originally, your connection polynomial is \$1+x+x^4+x^5+...
• 23.1k

### When does a feedback shift register count as non-linear?

Yes, you're right. XOR is considered a linear function in this case. So the feedback into the registers is linear. A non linear feedback shift register is a more generalised example where the ...
• 15.7k