Scrambler: Difference between revisions

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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.)
 
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)+1
       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

Mask
Polynomial mask for LFSR
Seed
Initial shift register contents
Length
Shift register length

Example Flowgraph

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

C++ files
TODO
Header files
TODO
Public header files
TODO
Block definition
TODO