Encrypt The first program you will write should be named encrypt.py. The job of

Question

Encrypt The first program you will write should be named encrypt.py. The job of this program will be to encrypt, "mix", the lines of a text file, but do it in such a way that it can be un-done later with a separate program which you will also write) When you run your program, your program will first request a file to to encrypt. Requesting the file name will look like: Enter the name of a file to encrypt: X The program will then run its encrypting algorithm on the file X. It will then save the encrypted version of the program to a file named encrypted.txt. You might be wondering how the encryption works and how can I mix in such a way that it can be undone by another program? Your program will "mix" an input file by randomly re-arranging the lines of the input file. For example, you might request that encrypt.py python file named get_credentials.py that looks like #get the username from a prompt username = raw_input(''Login : >> ") #11st of allowed users user1"Luke" user2 "Leia" #control that the user belongs to the list of allowed users if usernameuser1: print ("Access granted") print ("Welcome to the system") print ("Access denied") elif usernameuser2: else: You then run encrypt.py and request that it mix this file Enter the name of a file to encrypt: get-credentials. py

Explanation / Answer

------------------encrypt.py---------------------

import random

random.seed(123)

filename = raw_input("Enter the name of a file to encrypt: ")

file = open(filename)

lines = file.readlines()

file.close()

numOfLines = len(lines)

numSteps = len(lines)*3

for i in xrange(numOfLines):

lines[i] = (lines[i],i+1)

if(not lines[-1][0].endswith(" ")):

lines[-1] = (lines[-1][0]+" ",lines[-1][1])

for i in xrange(numSteps):

r1 = random.randint(0,numOfLines-1)

r2 = random.randint(0,numOfLines-1)

lines[r1],lines[r2] = lines[r2],lines[r1]

file2 = open("encrypted.txt","w")

for line in lines:

file2.write(line[0])

file2.close()

file3= open("mix.txt","w")

for line in lines:

file3.write(str(line[1]) + " ")

file3.close()

------------------decrypt.py---------------------

textFileName = raw_input("Enter the name of a mixed text file: ")

indexFileName = raw_input("Enter the mix index file: ")

file = open(textFileName)

lines = file.readlines()

file.close()

numLines = len(lines)

decrypted = [""]*numLines

indexFile = open(indexFileName)

i = 0

for line in indexFile:

num = int(line.strip())

decrypted[num-1] = lines[i]

i+=1

file2 = open("decrypted.txt","w")

for line in decrypted:

file2.write(line)

file2.close()

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