Python | Encoding Decoding using Matrix

Last Updated : 30 Dec, 2020

This article is about how we use the matrix to encode and decode a text message and simple strings.
Encoding process :

Take a String convert to corresponding number shown below
convert to 2D matrix(array). Now we have 2×2 matrix!
When we multiply this matrix with encoding matrix we get encoded 2×2 matrix.
now convert to vector(1D array) and Display to user

Decoding process

Take Encoded number convert into 2D matrix(array)

Inverse Encoding matrix!

Multiply Encoded matrix with inverse of encoding matrix.

convert to 1D Matrix(array).then convert to corresponding Alphabets.

Code : Encode.py

   # loading libraries 
import numpy as np 
  
a  =  [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] 
c  =  [[0,0,0,0,0,0,0,0,0,0], 
       [0,0,0,0,0,0,0,0,0,0]] 
  
# encode matrix 
ecm = [[3,4], [3,6]] 
i = 0
l = 0
   
# Lists of Alphabets and its values 
smallalpha = [" ","a", "b", "c", "d", "e", "f", "g", "h", 
              "i", "j", "k", "l", "m", "n", "o", "p", "q", 
              "r", "s", "t", "u", "v", "w", "x", "y", "z"] 
capitalalpha = [" ","A", "B", "C", "D", "E", "F", "G", "H", 
                "I", "J", "K", "L", "M", "N", "O", "P", "Q", 
                "R", "S", "T", "U", "V", "W", "X", "Y", "Z"] 
alphavalues = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 
               13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 
               23, 24, 25, 26, 27] 
  
# string to convert  
b = "India"
listb = list(b) 
lenb = len(listb) 
   
# Loop to convert Word to Values that  
# are further useful for Encoding 
for i in range(lenb): 
    for j in range(27): 
        if(listb[i]  == smallalpha[j]): 
            a[i] = alphavalues[j] 
            if(j  == 23): 
                j = 0
            break
        if(j  == 23): 
            for k in range(27): 
                if(listb[i]  == capitalalpha[k]): 
                    a[i] = alphavalues[k] 
                    break
                     
                   
if(lenb%2 == 1): 
    lenb = lenb+1
a = a[0:lenb] 
tb = b 
   
   
# convert this array to 2D array for further  
# multiplication with encoding matrix 
  
j = 0
k = 0
  
# b[m][n] m is always 2 
n = int(lenb/2) 
for i in range(0,lenb): 
    if(j<n): 
        c[k][j] = a[i] 
        j = j+1
    else: 
        k = k+1
        j = 0
        c[k][j] = a[i] 
        j = j+1
           
           
# Multiplay matrix by Encoding 2x2 matrix  
c = np.matmul(ecm, c) 
   
   
# Convert to 1D array for displaying  
i = 0
j = 0
k = 0
for i in range(2): 
    for j  in range(int(lenb/2)): 
        a[k] = c[i][j] 
        k = k+1
   
          
a = a[0:lenb] 
print("Encoding matrix  =  ", ecm) 
print("encrypted form =  ", a) 
 
  

Time Complexity : O(n)(where n is length of message)
Space Complexity : O(n)

Output:

  Encoding matrix =  [[3, 4], [3, 6]]  Encrypted form =  [63, 46, 12, 81, 48, 12]

Code : Decode.py

   # importing libraries 
import numpy as np 
from numpy.linalg import inv 
  
  
# Initial values 
a =[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
    0, 0, 0, 0, 0, 0, 0, 0] 
  
tdm =[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],  
      [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]] 
  
# encoding matrix 
ecm =[[3, 4], 
     [3, 6]] 
  
# Lists of Alphabets and its values 
smallalpha = [" ","a", "b", "c", "d", "e", "f", "g", "h", 
              "i", "j", "k", "l", "m", "n", "o", "p", "q", 
              "r", "s", "t", "u", "v", "w", "x", "y", "z"] 
capitalalpha = [" ","A", "B", "C", "D", "E", "F", "G", "H", 
                "I", "J", "K", "L", "M", "N", "O", "P", "Q", 
                "R", "S", "T", "U", "V", "W", "X", "Y", "Z"] 
alphavalues = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 
               13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 
               23, 24, 25, 26, 27] 
  
  
# Take inputs 
# elements in Encrypted Matrix 
lenb = 6
a = [63, 46, 12, 81, 48, 12] 
  
sobj = slice(lenb) 
a = a[sobj] 
  
  
# convert array to 2d matrix to further  
# multiplication with inverse of 2d matrix 
j = 0
k = 0
  
# b[m][n] m is always 2 
n = int(lenb / 2) 
for i in range(0, lenb): 
    if(j<n): 
        tdm[k][j]= a[i] 
        j = j + 1
    else: 
        k = k + 1
        j = 0
        tdm[k][j]= a[i] 
        j = j + 1
  
          
# Multiply by inverse matrix 
dcm = inv(ecm) 
dcm = np.matmul(dcm, tdm) 
  
  
# Convert to 1d array for extracting word 
i = 0
j = 0
k = 0
for i in range(2): 
    for j in range(int(lenb / 2)): 
        a[k]= dcm[i][j] 
        k = k + 1
           
  
# Creating a decoded word 
text = "" 
for i in range(0, lenb): 
    for j in range(0, 27): 
        if(a[i]== alphavalues[j]): 
            text =''.join([text, smallalpha[j]]) 
  
print("Decoded message = "+text) 
 
  

Time Complexity : O(n)(where n is number of elements)
Space Complexity : O(n)

Output:

Decoded message = india

Python - Convert Integer Matrix to String Matrix

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Python | Encoding Decoding using Matrix

Code : Encode.py

Code : Decode.py

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