Wikipedia: https:en.wikipedia.orgwikiEnigmamachine Video explanation: https:youtu.beQwQVMqfoB2E Also check out Numberphile's and Computerphile's videos on this topic This module contains function 'enigma' which emulates the famous Enigma machine from WWII. Module includes:  enigma function  showcase of function usage  9 randomly generated rotors  reflector aka static rotor  original alphabet Created by TrapinchO used alphabet  from string.asciiuppercase  default selection  rotors  reflector   extra rotors  Checks if the values can be used for the 'enigma' function  validator1,1,1, rotor1, rotor2, rotor3, 'POLAND' 1, 1, 1, 'EGZWVONAHDCLFQMSIPJBYUKXTR', 'FOBHMDKEXQNRAULPGSJVTYICZW',  'ZJXESIUQLHAVRMDOYGTNFWPBKC',  'P': 'O', 'O': 'P', 'L': 'A', 'A': 'L', 'N': 'D', 'D': 'N' :param rotpos: rotorpositon :param rotsel: rotorselection :param pb: plugb  validated and transformed :return: rotpos, rotsel, pb Checks if there are 3 unique rotors Checks if rotor positions are valid Validates string and returns dict https:en.wikipedia.orgwikiEnigmamachinePlugboard  plugboard'PICTURES' 'P': 'I', 'I': 'P', 'C': 'T', 'T': 'C', 'U': 'R', 'R': 'U', 'E': 'S', 'S': 'E'  plugboard'POLAND' 'P': 'O', 'O': 'P', 'L': 'A', 'A': 'L', 'N': 'D', 'D': 'N' In the code, 'pb' stands for 'plugboard' Pairs can be separated by spaces :param pbstring: string containing plugboard setting for the Enigma machine :return: dictionary containing converted pairs tests the input string if it a is type string b has even length so pairs can be made Checks if all characters are unique Created the dictionary The only difference with realworld enigma is that I allowed string input. All characters are converted to uppercase. nonletter symbol are ignored How it works: for every letter in the message  Input letter goes into the plugboard. If it is connected to another one, switch it.  Letter goes through 3 rotors. Each rotor can be represented as 2 sets of symbol, where one is shuffled. Each symbol from the first set has corresponding symbol in the second set and vice versa. example:  ABCDEFGHIJKLMNOPQRSTUVWXYZ  e.g. FD and DF  VKLEPDBGRNWTFCJOHQAMUZYIXS   Symbol then goes through reflector static rotor. There it is switched with paired symbol The reflector can be represented as2 sets, each with half of the alphanet. There are usually 10 pairs of letters. Example:  ABCDEFGHIJKLM  e.g. E is paired to X  ZYXWVUTSRQPON  so when E goes in X goes out and vice versa  Letter then goes through the rotors again  If the letter is connected to plugboard, it is switched.  Return the letter  enigma'Hello World!', 1, 2, 1, plugb'pictures' 'KORYH JUHHI!'  enigma'KORYH, juhhi!', 1, 2, 1, plugb'pictures' 'HELLO, WORLD!'  enigma'hello world!', 1, 1, 1, plugb'pictures' 'FPNCZ QWOBU!'  enigma'FPNCZ QWOBU', 1, 1, 1, plugb'pictures' 'HELLO WORLD' :param text: input message :param rotorposition: tuple with 3 values in range 1..26 :param rotorselection: tuple with 3 rotors  :param plugb: string containing plugboard configuration default '' :return: endecrypted string encryptiondecryption process  1st plugboard  rotor ra  rotor rb  rotor rc  reflector  this is the reason you don't need another machine to decipher 2nd rotors 2nd plugboard movesresets rotor positions else: pass Error could be also raised raise ValueError 'Invalid symbol'reprsymbol''
from __future__ import annotations

RotorPositionT = tuple[int, int, int]
RotorSelectionT = tuple[str, str, str]


# used alphabet --------------------------
# from string.ascii_uppercase
abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

# -------------------------- default selection --------------------------
# rotors --------------------------
rotor1 = "EGZWVONAHDCLFQMSIPJBYUKXTR"
rotor2 = "FOBHMDKEXQNRAULPGSJVTYICZW"
rotor3 = "ZJXESIUQLHAVRMDOYGTNFWPBKC"
# reflector --------------------------
reflector = {
    "A": "N",
    "N": "A",
    "B": "O",
    "O": "B",
    "C": "P",
    "P": "C",
    "D": "Q",
    "Q": "D",
    "E": "R",
    "R": "E",
    "F": "S",
    "S": "F",
    "G": "T",
    "T": "G",
    "H": "U",
    "U": "H",
    "I": "V",
    "V": "I",
    "J": "W",
    "W": "J",
    "K": "X",
    "X": "K",
    "L": "Y",
    "Y": "L",
    "M": "Z",
    "Z": "M",
}

# -------------------------- extra rotors --------------------------
rotor4 = "RMDJXFUWGISLHVTCQNKYPBEZOA"
rotor5 = "SGLCPQWZHKXAREONTFBVIYJUDM"
rotor6 = "HVSICLTYKQUBXDWAJZOMFGPREN"
rotor7 = "RZWQHFMVDBKICJLNTUXAGYPSOE"
rotor8 = "LFKIJODBEGAMQPXVUHYSTCZRWN"
rotor9 = "KOAEGVDHXPQZMLFTYWJNBRCIUS"


def _validator(
    rotpos: RotorPositionT, rotsel: RotorSelectionT, pb: str
) -> tuple[RotorPositionT, RotorSelectionT, dict[str, str]]:
    """
    Checks if the values can be used for the 'enigma' function

    >>> _validator((1,1,1), (rotor1, rotor2, rotor3), 'POLAND')
    ((1, 1, 1), ('EGZWVONAHDCLFQMSIPJBYUKXTR', 'FOBHMDKEXQNRAULPGSJVTYICZW', \
'ZJXESIUQLHAVRMDOYGTNFWPBKC'), \
{'P': 'O', 'O': 'P', 'L': 'A', 'A': 'L', 'N': 'D', 'D': 'N'})

    :param rotpos: rotor_positon
    :param rotsel: rotor_selection
    :param pb: plugb -> validated and transformed
    :return: (rotpos, rotsel, pb)
    """
    # Checks if there are 3 unique rotors

    if (unique_rotsel := len(set(rotsel))) < 3:
        msg = f"Please use 3 unique rotors (not {unique_rotsel})"
        raise Exception(msg)

    # Checks if rotor positions are valid
    rotorpos1, rotorpos2, rotorpos3 = rotpos
    if not 0 < rotorpos1 <= len(abc):
        msg = f"First rotor position is not within range of 1..26 ({rotorpos1}"
        raise ValueError(msg)
    if not 0 < rotorpos2 <= len(abc):
        msg = f"Second rotor position is not within range of 1..26 ({rotorpos2})"
        raise ValueError(msg)
    if not 0 < rotorpos3 <= len(abc):
        msg = f"Third rotor position is not within range of 1..26 ({rotorpos3})"
        raise ValueError(msg)

    # Validates string and returns dict
    pbdict = _plugboard(pb)

    return rotpos, rotsel, pbdict


def _plugboard(pbstring: str) -> dict[str, str]:
    """
    https://en.wikipedia.org/wiki/Enigma_machine#Plugboard

    >>> _plugboard('PICTURES')
    {'P': 'I', 'I': 'P', 'C': 'T', 'T': 'C', 'U': 'R', 'R': 'U', 'E': 'S', 'S': 'E'}
    >>> _plugboard('POLAND')
    {'P': 'O', 'O': 'P', 'L': 'A', 'A': 'L', 'N': 'D', 'D': 'N'}

    In the code, 'pb' stands for 'plugboard'

    Pairs can be separated by spaces
    :param pbstring: string containing plugboard setting for the Enigma machine
    :return: dictionary containing converted pairs
    """

    # tests the input string if it
    # a) is type string
    # b) has even length (so pairs can be made)
    if not isinstance(pbstring, str):
        msg = f"Plugboard setting isn't type string ({type(pbstring)})"
        raise TypeError(msg)
    elif len(pbstring) % 2 != 0:
        msg = f"Odd number of symbols ({len(pbstring)})"
        raise Exception(msg)
    elif pbstring == "":
        return {}

    pbstring.replace(" ", "")

    # Checks if all characters are unique
    tmppbl = set()
    for i in pbstring:
        if i not in abc:
            msg = f"'{i}' not in list of symbols"
            raise Exception(msg)
        elif i in tmppbl:
            msg = f"Duplicate symbol ({i})"
            raise Exception(msg)
        else:
            tmppbl.add(i)
    del tmppbl

    # Created the dictionary
    pb = {}
    for j in range(0, len(pbstring) - 1, 2):
        pb[pbstring[j]] = pbstring[j + 1]
        pb[pbstring[j + 1]] = pbstring[j]

    return pb


def enigma(
    text: str,
    rotor_position: RotorPositionT,
    rotor_selection: RotorSelectionT = (rotor1, rotor2, rotor3),
    plugb: str = "",
) -> str:
    """
    The only difference with real-world enigma is that I allowed string input.
    All characters are converted to uppercase. (non-letter symbol are ignored)
    How it works:
    (for every letter in the message)

    - Input letter goes into the plugboard.
    If it is connected to another one, switch it.

    - Letter goes through 3 rotors.
    Each rotor can be represented as 2 sets of symbol, where one is shuffled.
    Each symbol from the first set has corresponding symbol in
    the second set and vice versa.

    example:
    | ABCDEFGHIJKLMNOPQRSTUVWXYZ | e.g. F=D and D=F
    | VKLEPDBGRNWTFCJOHQAMUZYIXS |

    - Symbol then goes through reflector (static rotor).
    There it is switched with paired symbol
    The reflector can be represented as2 sets, each with half of the alphanet.
    There are usually 10 pairs of letters.

    Example:
    | ABCDEFGHIJKLM | e.g. E is paired to X
    | ZYXWVUTSRQPON | so when E goes in X goes out and vice versa

    - Letter then goes through the rotors again

    - If the letter is connected to plugboard, it is switched.

    - Return the letter

    >>> enigma('Hello World!', (1, 2, 1), plugb='pictures')
    'KORYH JUHHI!'
    >>> enigma('KORYH, juhhi!', (1, 2, 1), plugb='pictures')
    'HELLO, WORLD!'
    >>> enigma('hello world!', (1, 1, 1), plugb='pictures')
    'FPNCZ QWOBU!'
    >>> enigma('FPNCZ QWOBU', (1, 1, 1), plugb='pictures')
    'HELLO WORLD'


    :param text: input message
    :param rotor_position: tuple with 3 values in range 1..26
    :param rotor_selection: tuple with 3 rotors ()
    :param plugb: string containing plugboard configuration (default '')
    :return: en/decrypted string
    """

    text = text.upper()
    rotor_position, rotor_selection, plugboard = _validator(
        rotor_position, rotor_selection, plugb.upper()
    )

    rotorpos1, rotorpos2, rotorpos3 = rotor_position
    rotor1, rotor2, rotor3 = rotor_selection
    rotorpos1 -= 1
    rotorpos2 -= 1
    rotorpos3 -= 1

    result = []

    # encryption/decryption process --------------------------
    for symbol in text:
        if symbol in abc:
            # 1st plugboard --------------------------
            if symbol in plugboard:
                symbol = plugboard[symbol]

            # rotor ra --------------------------
            index = abc.index(symbol) + rotorpos1
            symbol = rotor1[index % len(abc)]

            # rotor rb --------------------------
            index = abc.index(symbol) + rotorpos2
            symbol = rotor2[index % len(abc)]

            # rotor rc --------------------------
            index = abc.index(symbol) + rotorpos3
            symbol = rotor3[index % len(abc)]

            # reflector --------------------------
            # this is the reason you don't need another machine to decipher

            symbol = reflector[symbol]

            # 2nd rotors
            symbol = abc[rotor3.index(symbol) - rotorpos3]
            symbol = abc[rotor2.index(symbol) - rotorpos2]
            symbol = abc[rotor1.index(symbol) - rotorpos1]

            # 2nd plugboard
            if symbol in plugboard:
                symbol = plugboard[symbol]

            # moves/resets rotor positions
            rotorpos1 += 1
            if rotorpos1 >= len(abc):
                rotorpos1 = 0
                rotorpos2 += 1
            if rotorpos2 >= len(abc):
                rotorpos2 = 0
                rotorpos3 += 1
            if rotorpos3 >= len(abc):
                rotorpos3 = 0

        # else:
        #    pass
        #    Error could be also raised
        #    raise ValueError(
        #       'Invalid symbol('+repr(symbol)+')')
        result.append(symbol)

    return "".join(result)


if __name__ == "__main__":
    message = "This is my Python script that emulates the Enigma machine from WWII."
    rotor_pos = (1, 1, 1)
    pb = "pictures"
    rotor_sel = (rotor2, rotor4, rotor8)
    en = enigma(message, rotor_pos, rotor_sel, pb)

    print("Encrypted message:", en)
    print("Decrypted message:", enigma(en, rotor_pos, rotor_sel, pb))
