One time pad

One Time Pad

Hi everyone, this is the homework of one time pad. Firstly one time pad is a concept  of cryptography, is a type of encryption algorithms by which the plain text is combined with a random key same length as the plain text and used only once. It was invented in 1917. If the key is truly random, never reused and, of course, is kept secret, it can be shown that the method of the one-time pad is unbreakable. 

So, for this homework i created a one time pad encryption using Python, i'll resume all my work in few steps. 

1 - I created the text files ("keys1.txt", and "keys2.txt")

These are all the keys generated(in both files: "keys1.txt", and "keys2.txt"). 10 different keys, but it doesn't matter because each message crypted and decrypted will generate different keys. The length of each key is 7  because this is the length of ASCII values (in binary).

2 - I requested to user for a string 

3 - Each character of the string gave by the user goes to the encrypt function.

4 - Then each character goes to the decrypt function

5 - Finally i printed out the binary value of the character, key used,  xor result, xor decrypted (using xor method again), ASCII value and the character decrypted.

Now, this is all my code...

	#!/usr/bin/python
	#Carlos Triana
	import random
	from numpy import *
	def createKeys():
	file1 = open('keys1.txt', 'w') #Creating file1
	file2 = open('keys2.txt', 'w') #Creating file2
	i = 0
	j = 0
	while i<10:
	while j<7:
	number = random.randint(0,2)
	file1.write(str(number)) #Filling file texts with
	file2.write(str(number)) #random numbers(binary)
	j = j +1
	file1.write("\n")
	file2.write("\n")
	j = 0
	i = i + 1
	file1.close()
	#crypt()
	def crypt(binary, size, i):
	st = ""
	st2 = ""
	xor = []
	file1 = open('keys1.txt', 'r') #Reading key
	st = file1.readline()
	key = list(st)
	j = 0
	while j < 7:
	if(binary[j] == key[j]): #Crypting character
	xor.append(0)
	else:
	xor.append(1)
	j = j+1
	decrypt(xor,binary, i, size)
	file1.close()
	if(i == size-1):
	createKeys()
	def decrypt(xor,binary, i, size):
	st2 = ""
	dec = []
	file2 = open('keys2.txt', 'r') #Reading keys
	st2 = file2.readline()
	key2 = list(st2)
	k = 0
	PreDecrypt = []
	while k < 7:
	number = 4
	number = int(key2[k])
	if(xor[k] == number): #Decrypting character(xor)
	dec.append(0)
	else:
	dec.append(1)
	k = k + 1
	file2.close()
	print "binary = " + str(binary) #This is the binary of the character
	print "key used = " + str(key2) #This is the key saved in the "keys2.txt" file
	print "xor or crypted = "+str(xor) #This is the key crypted (by xor)
	print "decrypted(binary) = "+str(dec)#This is the binary decrypted
	numero = "bla"
	numero = str(dec).strip('[]')
	numero = numero[::3] #Removing characters("," and " ")
	baseDiez = int(numero, 2)
	print "ASCII decrypted = "+str(baseDiez) #This is the ASCII value of the binary(character)
	decoder = chr(baseDiez)
	if (decoder == "@"): #For the "backspace" values
	decoder = " "
	if (baseDiez == 16): #For the "backspace" values
	decoder = " "
	print "Character decrypted = " + str(decoder) #This is the character decrypted
	print
	if(i == size-1): #If the character is the last one,
	createKeys() #create keys again(one time pad)
	def string2Binary():
	myInput = "" #Requesting a string
	myInput = raw_input('Get in a string to crypt it: ')
	newInput = list(myInput)
	size = len(myInput)
	binary = []
	i = 0
	while i < size:
	if (newInput[i] == " "):
	st = "001000000"
	else:
	st = bin(ord(newInput[i])) #Converting to binary
	st = st[2:] #I dont care first 2 values("0b")
	binary.append(st)
	crypt(binary[i], size, i) #Crypting the binary(previously character)
	i = i+1
	def main():
	createKeys()
	while True:
	number = input('Get in 1 to continue or 2 to exit: ') #1 to crypt/decrypt
	if (number == 1): #2 to exit
	string2Binary()
	else:
	break
	main()

view raw OneTimePad.py hosted with ❤ by GitHub

Finally this is mi program running (The message is: its)

If you want to write more messages you must to type 1 (if you type 2, program will close), and new messages will be crypted with other new key.


Leave your comment if you have any doubt

Thank you