After watching a video on numberphile thought it would be interesting to implement a virtual version on the Enigma cipher machine.
Step 1: Install Scala and Eclipse IDE for Scala.
http://www.scala-lang.org/downloads, http://scala-ide.org/
Step 2: Review the numberphile video and how the Enigma machine works
Step 3: Implement each function of the machine
- Rotors
- Rotor choices, rotors have different circuitry (0-24) – static value for each message
- Initial rotor combination (0-25) – static value for each message
- Rotor increment – Faster rotor, middle rotor, slow rotor
- Plug board
- 10 wires
- swapping 2 letters
- static value for each message
Step 4: Write an interface between the functions and a basic interface (text?)
Step 5: Test!
Conclusion: Using Scala (trying anyway) the implementation is not very complex. What is more difficult is replicating the original machines where the output character could not equal the input character. The limitation Turing used to crack the machines. Might see if I can implement that later then test out the cracking method. Not sure how easy it would be to break the current implementation…
CODE (EnigmaMachine.scala, EnigmaMachine.class):
// Virtual reconstruction of what the enigma machines did
// The replication is of the improved version where the input could result in the same output
object EnigmaMachine {
//////////////// ENCRYPTION/DECRYPTION FUNCTIONS \\\\\\\\\\\\\\\\\\\\\
//to replicate the simple machine circuit chars are converter to 0 - 25
def convertMessageToSimpleInt(rawInput: String):List[Int] = {
val userMessage = rawInput.toUpperCase
(for (x <- userMessage) yield if (x != 32) (x.toInt - 65) else 26).toList
}
//for all integers in the list, convert
def convertMessageToString(input: List[Int]): String = {
(for (x <- input) yield if (x == 26) " " else (x + 65).toChar).mkString
}
def enigmaGo(rotorChoices: List[Int], rotorPositions: List[Int], inputMessage: List[Int], encrypt: Boolean): List[Int] = {
// incrementing the rotors is dont based on the number of previous chars.. instead of the previous position
def incrementRots(nth: Int): List[Int] = {
val rot0 = (rotorPositions(0) + nth) % 26 //fast rotor
val rot1 = (rotorPositions(1) + (nth / 26)) % 26 //medium rotor
val rot2 = (rotorPositions(2) + ((nth / 26) /26)) % 26 //slow rotor
List(rot0, rot1, rot2)
}
//applies the rotor encryption then the scramble board
def transmuteElement(element: Int, rotPosApp: List[Int]): Int = {
val rotorTotal = rotorList(rotorChoices(0))(rotPosApp(0)) +
rotorList(rotorChoices(1))(rotPosApp(1)) +
rotorList(rotorChoices(2))(rotPosApp(2))
def scramble(inputVal:Int):Int = plugMap1.find(x => (x._1 == inputVal) || (x._2 == inputVal)) match {
case Some(y) => if (y._1 == inputVal) y._2 else y._1
case None => inputVal
}
if (element == 26) element
else if (encrypt) (scramble(element) + rotorTotal) % 26 else {
//decrypt is a bit messy atm :(
if (element - (rotorTotal % 26) < 0) scramble(element - (rotorTotal % 26) + 26) else scramble(element - (rotorTotal % 26))
}
}
//Accumulator hold the input and output lists, when input list is empty, return output.. also tail recursive
def enigmaAccu(remInput: List[Int], rotPos: List[Int], accumOutput: List[Int]): List[Int] = {
if (remInput.isEmpty) accumOutput
else enigmaAccu(remInput.tail, incrementRots(accumOutput.length), accumOutput:+(transmuteElement(remInput.head, rotPos)))
}
enigmaAccu(inputMessage, rotorPositions, Nil) //start the process
}
//////////////////// \\\\\\\\\\\\\\\\\\\\\\\\\
//////////////// UI STUFF \\\\\\\\\\\\\\\\\\\\\
def useMachine(rotorChoices: List[Int], rotorStartVals: List[Int], activity: String) = {
spamLine
val inputMessage = convertMessageToSimpleInt(askInput("Please enter a message to be " + activity + ", use only a-z: "))
val resultingMessage = enigmaGo(rotorChoices, rotorStartVals, inputMessage, if (activity == "encrypted") true else false)
spamLine
println("Your message has been " + activity + ": ")
println(convertMessageToString(resultingMessage))
spamLine
exit(0)
}
def getRotorChoices(s1:String, p: String => Boolean):List[Int] = {
val slot0 = getUserInput(s1 + "fast slot: ", "Entry Invalid.", p).mkString
val slot1 = getUserInput(s1 + "medium slot: ", "Entry Invalid.", p).mkString
val slot2 = getUserInput(s1 + "slow slot: ", "Entry Invalid.", p).mkString
List(slot0.toInt,slot1.toInt,slot2.toInt)
}
def spamLine = println("##############################################")
def askInput(statement: String) = {
val input = readLine(statement)
if (input == "") "99" else input
}
def askAgain(statement: String, f: => String) = {
println(statement)
f
}
def inputVals(f1: => String, f2: => String) = Stream.cons( f1, Stream.continually(f2))
def getUserInput(s1: String, s2: String, p:String => Boolean) = inputVals(askInput(s1), askAgain(s2, askInput(s1))).find(p)
//////////////////// \\\\\\\\\\\\\\\\\\\\\\\\\
//////////////// MAIN \\\\\\\\\\\\\\\\\\\\\
def main(args: Array[String]) {
println("### WELCOME TO THE ENIGMA MACHINE! ###" )
// GET INITIAL MACHINE SETTINGS FROM USER
// ROTOR PLACEMENT CONFIG
val rotorChoices = getRotorChoices("Choose rotor (0 - 4) for ", x => (x.toInt >= 0 && x.toInt < 5))
// ROTOR START VALS
val rotorStartVals = getRotorChoices("Choose rotor START VAL (0 - 25) for ", x => (x.toInt >= 0 && x.toInt < 25))
// PLUG MAP
println("There is only 1 plug map option at present:")
println(plugMap1.toString.drop(4))
//ENCRYPT OF DECRYPT - ONLY RELEVENT FOR GUI TEXT.. bleh not quite need to reverse circuit manually
val userChoice = getUserInput("Press 1 to encrypt, 2 to decrypt: ", "Entry Invalid.", x => (x == "2" || x == "1"))
userChoice.mkString match {
case "1" => useMachine(rotorChoices, rotorStartVals, "encrypted")
case "2" => useMachine(rotorChoices, rotorStartVals, "decrypted")
case default => exit(0)
}
}
//////////////////// \\\\\\\\\\\\\\\\\\\\\\\\\
//////////////// CONSTANTS \\\\\\\\\\\\\\\\\\\\\
val rotorList = List(List(6, 17, 4, 3, 23, 22, 21, 5, 0, 19, 20, 11, 16, 9, 13, 24, 18, 1, 8, 2, 7, 10, 12, 14, 25, 15)
,List(2, 7, 23, 12, 13, 15, 18, 1, 8, 11, 0, 3, 10, 5, 24, 4, 17, 19, 6, 9, 20, 14, 25, 21, 16, 22)
,List(23, 1, 19, 18, 0, 10, 3, 8, 9, 21, 2, 12, 13, 14, 24, 6, 20, 16, 11, 17, 15, 7, 4, 25, 22, 5)
,List(21, 22, 16, 2, 18, 20, 15, 9, 5, 1, 17, 10, 3, 6, 0, 13, 11, 23, 4, 12, 19, 8, 7, 25, 24, 14)
,List(25, 3, 11, 7, 5, 15, 24, 10, 21, 6, 12, 17, 8, 23, 2, 18, 19, 14, 4, 0, 20, 9, 22, 1, 16, 13))
val plugMap1 = List((3,7),(11,16),(18,24),(17,9),(21,19),(14,13),(0,12),(1,25),(22,20),(4,6))
//////////////////// \\\\\\\\\\\\\\\\\\\\\\\\\
}
