Amazing-Python-Scripts

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import math
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import sys
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# Caesar Cipher decryption function
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def caesar_decrypt(ciphertext, shift):
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    plaintext = ""
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    for char in ciphertext:
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        if char.isalpha():
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            ascii_offset = 65 if char.isupper() else 97
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            decrypted_char = chr(
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                (ord(char) - shift - ascii_offset) % 26 + ascii_offset)
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            plaintext += decrypted_char
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        else:
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            plaintext += char
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    return plaintext
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# Transposition Cipher decryption function
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def trans_decrypt(en_msg, k):
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    message = en_msg
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    key = k
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    numOfColumns = int(math.ceil(len(message) / float(key)))
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    numOfRows = k
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    numOfShadedBoxes = (numOfColumns * numOfRows) - len(message)
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    plaintext = [''] * numOfColumns
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    column = 0
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    row = 0
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    for symbol in message:
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        plaintext[column] += symbol
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        column += 1  # Point to the next column.
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        if (column == numOfColumns) or (column == numOfColumns - 1 and row >= numOfRows - numOfShadedBoxes):
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            column = 0
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            row += 1
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    return ''.join(plaintext)
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# Main program
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def main():
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    don_know = "[If you don't know the shift/key just press enter; the script will try all possible combinations then]"
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    print("Welcome to the Encryption Decryption Program!")
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    # Prompt user for encryption method
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    try:
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        method = int(input(
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            "Which encryption method would you like to decrypt?\nChoose number\n1) Caesar\n2) Transposition\n>"))
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    except ValueError:
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        print("Invalid selection")
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        sys.exit()
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    # Prompt user for ciphertext
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    ciphertext = input("Enter the ciphertext to decrypt: ")
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    # Decrypt based on chosen method
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    if method == 1 and len(ciphertext) != 0:
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        shift = input(
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            f"Enter the shift value used in the Caesar cipher:\n{don_know}\n>")
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        if shift == '':
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            for i in range(1, 26):
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                plaintext = caesar_decrypt(ciphertext, i)
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                print(plaintext)
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        elif shift.isnumeric():
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            shift = int(shift)
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            plaintext = caesar_decrypt(ciphertext, shift)
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            print(plaintext)
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        else:
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            print('Invalid Command')
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    elif method == 2 and len(ciphertext) != 0:
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        key = input(
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            f"Enter the key used in the transposition cipher:\n{don_know}\n>")
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        if key == '':
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            for i in range(1, 26):
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                plaintext = trans_decrypt(ciphertext, i)
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                print(plaintext)
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        elif key.isnumeric():
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            key = int(key)
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            plaintext = trans_decrypt(ciphertext, key)
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            print(plaintext)
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        else:
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            print('Invalid Command')
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    else:
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        print("Invalid encryption method specified or No cipher text is given")
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# Run the program
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if __name__ == "__main__":
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    main()
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