API LFSR

class(fpoly=[5,2], initstate=’ones’, verbose=False)

help doc

Linear Feedback Shift Register

#Parameters ————————————

• initstatebinary np.array (row vector) or str =’ones’ or ‘random’, optional (default = ‘ones’)) Initial state of LFSR. default =’ones’

  Initial state is intialized with ones and length of register is equal to degree of feedback polynomial if state=’rand’, initial state is intialized with random binary sequence of length equal to degree of feedback polynomial

• fpolyList, optional (default=[5,2])

  Feedback polynomial, it has to be primitive polynomial of GF(2) field, for valid output of LFSR to get the list of feedback polynomials check method ‘get_fpolyList’ or check Refeferece: Ref: List of some primitive polynomial over GF(2)can be found at http://www.partow.net/programming/polynomials/index.html http://www.ams.org/journals/mcom/1962-16-079/S0025-5718-1962-0148256-1/S0025-5718-1962-0148256-1.pdf http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf

• verboseboolean, optional (default=False)

  if True, state of LFSR will be printed at every cycle(iteration)

#Attributes ————————————

• countint

  Count the cycle

• seqnp.array shape =(count,)

  Output sequence stored in seq since first cycle. If -1, no cycle has been excecuted, count =0

• outbitbinary bit

  Current output bit, Last bit of current state if -1, no cycle has been excecuted, count =0

• feedbackbitbinary bit

  If -1, no cycle has been excecuted, count =0

• Mint

  length of LFSR, M-bit LFSR,

• expectedPeriodint

  Expected period of sequence if feedback polynomial is primitive and irreducible (as per reference), period will be 2^M -1

• feedpolystr

  feedback polynomial

#Methods ————————————

• next()

  run one cycle on LFSR with given feedback polynomial and update the count, state, feedback bit, output bit and seq

  return: binary bit output bit : binary

• runKCycle(k)

  run k cycles and update all the Parameters

  return tempseq : shape =(k,)

  output binary sequence of k cycles

• runFullCycle()

  run full cycle ( = 2^M-1)

  return seq : binary output sequence since start: shape = (count,)

• set(fpoly,state=’ones’)

  set feedback polynomial and state

  fpoly : list feedback polynomial like [5,4,3,2]

  state : np.array, like np.array([1,0,0,1,1]), default =’ones’ Initial state is intialized with ones and length of register is equal to degree of feedback polynomial if state=’rand’, initial state is intialized with random binary sequence of length equal to degree of feedback polynomial

• reset()

  Reseting LFSR to its initial state and count to 0

• changeFpoly(newfpoly, reset=False)

  Changing Feedback polynomial newfpoly : list like, [5,4,2,1], changing the feedback polynomial

  reset : boolean default=False if True, reset all the Parameters : count=0, seq=-1.. if False, leave the LFSR as it is only change the feedback polynomial as used in ‘Enhancement of A5/1: Using variable feedback polynomials of LFSR’ ref: 10.1109/ETNCC.2011.5958486

• check()

  check if -degree of feedback polynomial <= length of LFSR >=1 -given intistate of LFSR is correct

• info()

  display the information about LFSR with current state of variables

• get_fpolyList(m=None)

  Get the list of primitive polynomials as feedback polynomials for m-bit LFSR if m is None, list of feedback polynomials for 1 < m < 32 is return as a dictionary

• get_Ifpoly(fpoly)

  Get the image of primitive polynomial fpoly, which is also a valid primitive polynomial