Question

write a python program that ciphers a plain text message using double transposition scheme and vise versa. The program should accept five tuples of input: plain text, row, column, permutation of row and columns.

Pain Text: attack at dawn

Matrix Row Size: 5

Matrix Column Size: 3

Row Permutation Order: 3,5,1,4,2

Column permutation order: 1,3,2

Encrypted Text:

Answer 1

Solution:
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Please find below instructions, code and snipptet

Instructions :

The indentation may not get presevred in check editor, so please check indentation when you paste. Attached screenshot of code to help you with that

Code

## python 2

text = raw_input("Enter Text : ") # take user input
encOrDec = int(input("Enter 0 to encrypt and 1 to decrypt : "))
nRowsMat = int(input("Matrix row size : "))
nColsMat = int(input("Matrix col size : "))
RowPermutationOrder = input("Row permutation order (python list) : ")
ColPermutationOrder = input("Column permutation order (python list) : ")

msgMatrix =[] # will hold initial message

for i in range (0,nRowsMat):
temp=[]
for j in range (0,nColsMat):
if(nColsMat*i+j < len(text)):
if(text[nColsMat*i+j] == ' '): # fill initialmatrix with the message rowwise, replalace spaces with 'x'
temp.append('x')
else:
temp.append(text[nColsMat*i+j])
else:
temp.append('x')
msgMatrix.append(temp)

rowPermutedMatrix = []

for row in RowPermutationOrder: # for each row
rowPermutedMatrix.append(msgMatrix[row-1]) # permute the rows

colPermutedMatrix = [['0']*nColsMat for _ in range(nRowsMat)] # initalize variable to store matrix after colPermutation

startCol=-1
for col in ColPermutationOrder:
colVals=list([])
for i in range(0,nRowsMat):
colVals.append(rowPermutedMatrix[i][col-1]) # extract value of current column

startCol = startCol + 1

for i in range(0,nRowsMat):
colPermutedMatrix[i][startCol] = colVals[i] # put the first column in permuted matrix
  
cipheredMsg =''
for i in range(0,nRowsMat):
for j in range(0, nColsMat):
if(encOrDec==1 and colPermutedMatrix [i][j] == 'x'): # if user is deciphering reverse 'x' with spaces
colPermutedMatrix [i][j] = ' '   
cipheredMsg = cipheredMsg + colPermutedMatrix [i][j]

print("Output message is : ")
print(cipheredMsg)

Snippets of Code and Output