Generators

A5/1 GSM Stream cipher generator

Ref: https://en.wikipedia.org/wiki/A5/1

Image Socuce: https://en.wikipedia.org/wiki/A5/1

import numpy as np
import matplotlib.pyplot as plt
from pylfsr import A5_1

A5 = A5_1(key='random')
print('key: ',A5.key)
A5.R1.Viz(title='R1')
A5.R2.Viz(title='R2')
A5.R3.Viz(title='R3')

print('key: ',A5.key)
print()
print('count \t cbit\t\tclk\t R1_R2_R3\toutbit \t seq')
print('-'*80)
for _ in range(15):
    print(A5.count,A5.getCbits(),A5.clock_bit,A5.getLastbits(),A5.outbit,A5.getSeq(),sep='\t')
    A5.next()
print('-'*80)
print('Output: ',A5.seq)

A5.runKCycle(1000)
A5.getSeq()

Enhanced A5/1

Reference Article: Enhancement of A5/1: https://doi.org/10.1109/ETNCC.2011.5958486

# Three LFSRs initialzed with 'ones' though they are intialized with encription key
R1 = LFSR(fpoly = [19,18,17,14])
R2 = LFSR(fpoly = [23,22,21,8])
R3 = LFSR(fpoly = [22,21])

# clocking bits
b1 = R1.state[8]
b2 = R3.state[10]
b3 = R3.state[10]

Geffe Generator

Ref: Schneier, Bruce. Applied cryptography: protocols, algorithms, and source code in C. john wiley & sons, 2007.

Chaper 16

import numpy as np
import matplotlib.pyplot as plt
from pylfsr import Geffe, LFSR

kLFSR = [LFSR(initstate='random') for _ in range(8)]  # List of 8 5-bit LFSRs with default feedback polynomial and random initial state
cLFSR = LFSR(initstate='random')                      # A 5-bit LFSR with for selecting one of 8 output at a time

GG = Geffe(kLFSR_list=kLFSR, cLFSR=cLFSR)

print('key: ',GG.getState())
print()
for _ in range(50):
    print(GG.count,GG.m_count,GG.outbit_k,GG.sel_k,GG.outbit,GG.getSeq(),sep='\t')
    GG.next()

GG.runKCycle(1000)
GG.getSeq()