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Questions tagged [shift-register]

Shift registers are at the heart of cryptography and error-correction. In cryptography they are the main tool for generating long pseudorandom binary sequences which can be used as keys for two communicating parties in symmetric cryptography. Practically all military cryptography makes use of them.

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Linear Feedback Shift Register Taps

Linear feedback shift register tap charts are availale for registers of length 3 to 168. Does anyone have a chart for register lengths from 168 to 256 or beyond?
0 votes
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Question about obtaining a keystream from a linear-feedback shift register

For a homework question we are obtaining a keystream from a LFSR and I am slightly confused on which digits are used as the key. For example I have this table here, ...
1 vote
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How to build a lsfr based on sequence $s_i = s_{i-1} + s_{i-4}$? [closed]

How do I know where my XOR gates go? What does the F2 stand for here? Also the next task is to generate the sequence (with initialisation vector $s_0 = 1, s_1 = s_2 = s_3 = 0$) until it becomes ...
2 votes
1 answer

Cryptanalysis of a feedback shift reigister with an S-box

I’m just getting started on learning cryptography and here is a problem from exercises about which I'm totally confused: This is a 32-bit feedback shift register to encrypt some message. The register ...
1 vote
1 answer

Shift-rotating random number generator

Let $\omega$ denote the set of non-negative integers. For $n\in\omega\setminus\{0\} $ define the rotation function $$\text{rot}_n:\{0,1\}^n \to \{0,1\}^n$$ by $x \mapsto x'$ where $x'_k = x_{k+1}$ ...
2 votes
1 answer

autocorrelation of non-linear shift register with the period of $2^n$ (full period)

throughout the question I will talk about sequences in bipolar alphabet, meaning, over {1,-1}. I have read in the book Shift Register Sequences by Solomon W. Golomb that sequences with the period of $...
1 vote
1 answer

How to calculate period of stream cipher with multiple LFSR and NLFSR

I am interested in knowing how to calculate period of a stream cipher with more than one FSR (linear as well as non linear). I know for a single FSR, period can be calculated with farmula q^L-1 where ...
11 votes
1 answer

What are the methods to construct a primitive binary nonlinear feedback shift register (NLFSR)?

Given a binary shift register of $n$ bits, a primitive binary nonlinear feedback shift register will generate a sequence with a period of $2^n - 1$. While I am unable to find a paper which directly ...
2 votes
1 answer

Upper bound Linear Feedback Shift Register

It is clear that when we have any output stream $x_0,x_1,...$ produced by linear-feedback shift register, then this output has to be periodic. Now I was wondering if we can find an upper bound for ...
4 votes
2 answers

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

It seems that a feedback shift register is counted as a linear feedback shift register whenever it only includes XOR operations. This leads me to believe that a non-linear feedback shift register is ...
5 votes
1 answer

The role of Shift Register Cascades in Cryptography?

Clearly, there are stages when binary bits are needed and this can be done with the help of Linear Feedback Shift Registers. Registers are required to be connected in such a manner that one register ...