# Difference between revisions of "Scrambler"

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(Added a help-function for those who want to create the mask and length from a polynomial expression.) |
(Yeah there was a typo, now it's fixed. Sorry.) |
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Line 23: | Line 23: | ||

def make_mask(*exp): | def make_mask(*exp): | ||

from functools import reduce | from functools import reduce | ||

return reduce(int.__xor__,map(lambda x:2**x,exp)),max(exp) | return reduce(int.__xor__,map(lambda x:2**x,exp)),max(exp)-1 | ||

mask,k = make_mask(5,3,0) # mask and length for p(x) = x^5 + x^3 + 1, a primitive polynomial in GF(2) | mask,k = make_mask(5,3,0) # mask and length for p(x) = x^5 + x^3 + 1, a primitive polynomial in GF(2) | ||

## Latest revision as of 15:03, 27 November 2020

Scramble an input stream using an LFSR.

This block works on the LSB only of the input data stream, i.e., on an "unpacked binary" stream, and produces the same format on its output.

## Parameters[edit]

- Mask
- Polynomial mask for LFSR

- Seed
- Initial shift register contents

- Length
- Shift register length

## Example Flowgraph[edit]

Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI. Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately. The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.

Here is a simple python-function to create the mask and length from the exponents of a polynomial:

def make_mask(*exp): from functools import reduce return reduce(int.__xor__,map(lambda x:2**x,exp)),max(exp)-1 mask,k = make_mask(5,3,0) # mask and length for p(x) = x^5 + x^3 + 1, a primitive polynomial in GF(2)

## Source Files[edit]

- C++ files
- TODO

- Header files
- TODO

- Public header files
- TODO

- Block definition
- TODO