118 lines
5.8 KiB
Python
118 lines
5.8 KiB
Python
# Python Caeser Cipher Helper v1.1.0
|
|
# Usage (encrypt): python3 caeser-cipher.py encrypt secretmessage
|
|
# Usage (decrypt): python3 caeser-cipher.py decrypt secretmessage
|
|
|
|
import re # Import Regex tools
|
|
import string # Import string tools
|
|
import collections # Import tools to sort letters.
|
|
from sys import argv # Import tool to process command line arguments.
|
|
|
|
#if action == "help": # If error, print help https://stackoverflow.com/questions/4042452/display-help-message-with-python-argparse-when-script-is-called-without-any-argu
|
|
#print("\nUsage (encrypt): python3 caeser-cipher.py encrypt secretmessage")
|
|
#print("Usage (decrypt): python3 caeser-cipher.py decrypt secretmessage\n")
|
|
|
|
script, action, ciphertext = argv # Take command line input.
|
|
|
|
#ciphertext = input("Please type in your cipher text:") # Set variable cipertext to the input from user.
|
|
shiftNum = input("Please enter the shift you would like to use (Just hit enter if you don't know the shift used):") # Get input
|
|
#action = input("Please enter encrypt or decrypt):") # Get input
|
|
ciphertext = re.sub (r'([^a-zA-Z]+?)', '', ciphertext) # Remove all non-letters.
|
|
ciphertext = ciphertext.lower() # Make it all lowercase. https://www.geeksforgeeks.org/isupper-islower-lower-upper-python-applications/
|
|
letters = list(string.ascii_lowercase) # Use a list of lowercase letters. https://stackoverflow.com/questions/43918437/how-to-iterate-through-the-alphabet
|
|
|
|
def encrypt(ciphertext, shiftNum, letters): # Grab parameters
|
|
|
|
# Create local variables for this function.
|
|
|
|
letterCount = 0
|
|
letterPos = 0
|
|
answer = ""
|
|
|
|
for c in ciphertext: # For every letter in the ciphertext
|
|
while letterPos < 26: # While the letter's position in the alphabet is less than 26 (and thus valid), continue.
|
|
|
|
if ciphertext[letterCount] == letters[letterPos]: # Match the letter in the ciphertext to a letter in the alphabet and once they match, continue.
|
|
letter = int(letterPos) + int(shiftNum) # Take the position of the letter and the shift number and add them for the enciphered letter.
|
|
|
|
if letter > 25: # If the enciphered letter's position is not valid because it is too high, fix it by rotating around the alphabet.
|
|
letter = letter - 26
|
|
if letter < 0:
|
|
letter = letter + 26 # If the enciphered letter's position is not valid because it is too low, fix it by rotating around the alphabet.
|
|
|
|
answer = answer + letters[letter] # Add letters together to get the enciphered text.
|
|
|
|
letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
|
|
|
|
if letterPos > 25: # If the letter position is greater than 25, cycle back through the alphabet.
|
|
letterPos = letterPos - 26
|
|
|
|
letterCount = letterCount + 1 # Keep track of how many times we're doing this.
|
|
|
|
print("\nYour enciphered text is: " + answer)
|
|
|
|
|
|
def decrypt(ciphertext, shiftNum, letters, commonletter): # Grab parameters
|
|
|
|
# Create local variables for this function.
|
|
|
|
letterCount = 0
|
|
letterPos = 0
|
|
answer = ""
|
|
|
|
for c in ciphertext: # For every letter in the ciphertext
|
|
while letterPos < 26: # While the letter's position in the alphabet is less than 26 (and thus valid), continue.
|
|
|
|
if ciphertext[letterCount] == letters[letterPos]: # Match the letter in the ciphertext to a letter in the alphabet and once they match, continue.
|
|
letter = int(letterPos) - int(shiftNum) # Take the position of the letter and the shift number and add them for the enciphered letter.
|
|
|
|
if letter > 25: # If the enciphered letter's position is not valid because it is too high, fix it by rotating around the alphabet.
|
|
letter = letter - 26
|
|
if letter < 0:
|
|
letter = letter + 26 # If the enciphered letter's position is not valid because it is too low, fix it by rotating around the alphabet.
|
|
|
|
answer = answer + letters[letter] # Add letters together to get the enciphered text.
|
|
|
|
letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
|
|
|
|
if letterPos > 25: # If the letter position is greater than 25, cycle back through the alphabet.
|
|
letterPos = letterPos - 26
|
|
|
|
letterCount = letterCount + 1 # Keep track of how many times we're doing this.
|
|
|
|
print("\nYour decrypted text is: " + answer)
|
|
|
|
|
|
def freq(ciphertext):
|
|
# Create local variables for this function.
|
|
|
|
commonletter = 0
|
|
letterCount = 0
|
|
letterPos = 0
|
|
answer = ""
|
|
|
|
commonletter = collections.Counter(ciphertext).most_common()[0][0] # Find most common letter and thus the shift https://stackoverflow.com/questions/47251934/how-to-count-the-most-frequent-letter-in-a-string
|
|
|
|
for c in ciphertext:
|
|
while letterPos < 26:
|
|
|
|
if not commonletter == 0:
|
|
if commonletter == letters[letterPos]: # If the most frequent letter matches the current letter, set the shift to that letter because that is the shift for the cipher. Forgot the double equals for comparison.
|
|
|
|
shiftNum = letterPos - 4
|
|
|
|
if letterPos > 25: # If the letter position is greater than 25, cycle back through the alphabet.
|
|
letterPos = letterPos - 26
|
|
|
|
letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
|
|
|
|
decrypt(ciphertext, shiftNum, letters, commonletter) # Decrypt using the frequency found in here.
|
|
|
|
|
|
if action == "encrypt":
|
|
encrypt(ciphertext, shiftNum, letters) # Start the encrypt() function while passing 3 variables as parameters.
|
|
if action == "decrypt":
|
|
if shiftNum == "":
|
|
freq(ciphertext)
|
|
else:
|
|
decrypt(ciphertext, shiftNum, letters, commonletter)
|