116 lines
5.5 KiB
Python
116 lines
5.5 KiB
Python
# Python Caeser Cipher Helper v1.2.0
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# Usage (encrypt): python3 caeser-cipher.py encrypt secretmessage
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# Usage (decrypt): python3 caeser-cipher.py decrypt secretmessage
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import re # Import Regex tools
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import string # Import string tools
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import collections # Import tools to sort letters.
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import argparse
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parser = argparse.ArgumentParser(usage="(encrypt): python3 caeser-cipher.py encrypt [secretmessage] [shift]\nusage: (decrypt): python3 caeser-cipher.py decrypt [secretmessage] [shift]\nusage: If you don't know the shift of encrypted text, use 0\nusage: For example: python3 caeser-cipher.py decrypt hhhhh 0")
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parser.add_argument("action")
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parser.add_argument("ciphertext")
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parser.add_argument("shiftNum")
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args = parser.parse_args()
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shiftNum = args.shiftNum
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ciphertext = re.sub (r'([^a-zA-Z]+?)', '', args.ciphertext) # Remove all non-letters.
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ciphertext = ciphertext.lower() # Make it all lowercase. https://www.geeksforgeeks.org/isupper-islower-lower-upper-python-applications/
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letters = list(string.ascii_lowercase) # Use a list of lowercase letters. https://stackoverflow.com/questions/43918437/how-to-iterate-through-the-alphabet
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def encrypt(ciphertext, shiftNum, letters): # Grab parameters
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# Create local variables for this function.
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letterCount = 0
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letterPos = 0
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answer = ""
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for c in ciphertext: # For every letter in the ciphertext
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while letterPos < 26: # While the letter's position in the alphabet is less than 26 (and thus valid), continue.
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if ciphertext[letterCount] == letters[letterPos]: # Match the letter in the ciphertext to a letter in the alphabet and once they match, continue.
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letter = int(letterPos) + int(shiftNum) # Take the position of the letter and the shift number and add them for the enciphered letter.
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if letter > 25: # If the enciphered letter's position is not valid because it is too high, fix it by rotating around the alphabet.
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letter = letter - 26
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if letter < 0:
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letter = letter + 26 # If the enciphered letter's position is not valid because it is too low, fix it by rotating around the alphabet.
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answer = answer + letters[letter] # Add letters together to get the enciphered text.
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letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
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if letterPos > 25: # If the letter position is greater than 25, cycle back through the alphabet.
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letterPos = letterPos - 26
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letterCount = letterCount + 1 # Keep track of how many times we're doing this.
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return print("\nYour enciphered text is: " + answer)
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def decrypt(ciphertext, shiftNum, letters): # Grab parameters
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# Create local variables for this function.
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letterCount = 0
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letterPos = 0
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answer = ""
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for c in ciphertext: # For every letter in the ciphertext
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while letterPos < 26: # While the letter's position in the alphabet is less than 26 (and thus valid), continue.
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if ciphertext[letterCount] == letters[letterPos]: # Match the letter in the ciphertext to a letter in the alphabet and once they match, continue.
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letter = int(letterPos) - int(shiftNum) # Take the position of the letter and the shift number and add them for the enciphered letter.
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if letter > 25: # If the enciphered letter's position is not valid because it is too high, fix it by rotating around the alphabet.
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letter = letter - 26
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if letter < 0:
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letter = letter + 26 # If the enciphered letter's position is not valid because it is too low, fix it by rotating around the alphabet.
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answer = answer + letters[letter] # Add letters together to get the enciphered text.
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letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
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if letterPos > 25: # If the letter position is greater than 25, cycle back through the alphabet.
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letterPos = letterPos - 26
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letterCount = letterCount + 1 # Keep track of how many times we're doing this.
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return print("\nYour decrypted text is: " + answer)
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def freq(ciphertext):
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# Create local variables for this function.
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commonletter = 0
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letterCount = 0
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letterPos = 0
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answer = ""
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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
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for c in ciphertext:
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while letterPos < 26:
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if not commonletter == 0:
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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.
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shiftNum = letterPos - 4
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if letterPos > 25: # If the letter position is greater than 25, cycle back through the alphabet.
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letterPos = letterPos - 26
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letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
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decrypt(ciphertext, shiftNum, letters) # Decrypt using the frequency found in here.
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if args.action == "encrypt":
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encrypt(ciphertext, shiftNum, letters) # Start the encrypt() function while passing 3 variables as parameters.
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if args.action == "decrypt":
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if shiftNum == "0":
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freq(ciphertext)
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else:
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decrypt(ciphertext, shiftNum, letters)
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