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Task/One-time-pad/Kotlin/one-time-pad.kotlin
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Task/One-time-pad/Kotlin/one-time-pad.kotlin
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// version 1.2.31
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import java.io.File
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import java.security.SecureRandom
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const val CHARS_PER_LINE = 48
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const val CHUNK_SIZE = 6
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const val COLS = 8
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const val DEMO = true // would normally be set to false
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enum class FileType { OTP, ENC, DEC }
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fun Char.isAlpha() = this in 'A'..'Z'
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fun String.toAlpha() = this.filter { it.isAlpha() }
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fun String.isOtpRelated() = endsWith(".1tp") || endsWith(".1tp_cpy") ||
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endsWith(".1tp_enc") || endsWith(".1tp_dec")
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fun makePad(nLines: Int): String {
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val nChars = nLines * CHARS_PER_LINE
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val sr = SecureRandom()
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val sb = StringBuilder(nChars)
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/* generate random upper case letters */
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for (i in 0 until nChars) sb.append((sr.nextInt(26) + 65).toChar())
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return sb.toString().inChunks(nLines, FileType.OTP)
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}
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fun vigenere(text: String, key: String, encrypt: Boolean = true): String {
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val sb = StringBuilder(text.length)
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for ((i, c) in text.withIndex()) {
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val ci = if (encrypt)
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(c.toInt() + key[i].toInt() - 130) % 26
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else
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(c.toInt() - key[i].toInt() + 26) % 26
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sb.append((ci + 65).toChar())
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}
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val temp = sb.length % CHARS_PER_LINE
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if (temp > 0) { // pad with random characters so each line is a full one
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val sr = SecureRandom()
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for (i in temp until CHARS_PER_LINE) sb.append((sr.nextInt(26) + 65).toChar())
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}
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val ft = if (encrypt) FileType.ENC else FileType.DEC
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return sb.toString().inChunks(sb.length / CHARS_PER_LINE, ft)
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}
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fun String.inChunks(nLines: Int, ft: FileType): String {
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val chunks = this.chunked(CHUNK_SIZE)
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val sb = StringBuilder(this.length + nLines * (COLS + 1))
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for (i in 0 until nLines) {
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val j = i * COLS
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sb.append(" ${chunks.subList(j, j + COLS).joinToString(" ")}\n")
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}
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val s = " file\n" + sb.toString()
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return when (ft) {
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FileType.OTP -> "# OTP" + s
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FileType.ENC -> "# Encrypted" + s
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FileType.DEC -> "# Decrypted" + s
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}
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}
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fun menu(): Int {
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println("""
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|1. Create one time pad file.
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|2. Delete one time pad file.
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|3. List one time pad files.
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|4. Encrypt plain text.
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|5. Decrypt cipher text.
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|6. Quit program.
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""".trimMargin())
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var choice: Int?
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do {
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print("Your choice (1 to 6) : ")
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choice = readLine()!!.toIntOrNull()
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}
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while (choice == null || choice !in 1..6)
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return choice
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}
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fun main(args: Array<String>) {
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mainLoop@ while (true) {
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val choice = menu()
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println()
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when (choice) {
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1 -> { // Create OTP
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println("Note that encrypted lines always contain 48 characters.\n")
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print("OTP file name to create (without extension) : ")
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val fileName = readLine()!! + ".1tp"
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var nLines: Int?
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do {
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print("Number of lines in OTP (max 1000) : ")
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nLines = readLine()!!.toIntOrNull()
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}
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while (nLines == null || nLines !in 1..1000)
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val key = makePad(nLines)
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File(fileName).writeText(key)
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println("\n'$fileName' has been created in the current directory.")
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if (DEMO) {
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// a copy of the OTP file would normally be on a different machine
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val fileName2 = fileName + "_cpy" // copy for decryption
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File(fileName2).writeText(key)
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println("'$fileName2' has been created in the current directory.")
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println("\nThe contents of these files are :\n")
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println(key)
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}
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}
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2 -> { // Delete OTP
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println("Note that this will also delete ALL associated files.\n")
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print("OTP file name to delete (without extension) : ")
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val toDelete1 = readLine()!! + ".1tp"
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val toDelete2 = toDelete1 + "_cpy"
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val toDelete3 = toDelete1 + "_enc"
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val toDelete4 = toDelete1 + "_dec"
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val allToDelete = listOf(toDelete1, toDelete2, toDelete3, toDelete4)
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var deleted = 0
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println()
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for (name in allToDelete) {
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val f = File(name)
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if (f.exists()) {
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f.delete()
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deleted++
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println("'$name' has been deleted from the current directory.")
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}
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}
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if (deleted == 0) println("There are no files to delete.")
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}
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3 -> { // List OTPs
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println("The OTP (and related) files in the current directory are:\n")
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val otpFiles = File(".").listFiles().filter {
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it.isFile() && it.name.isOtpRelated()
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}.map { it.name }.toMutableList()
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otpFiles.sort()
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println(otpFiles.joinToString("\n"))
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}
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4 -> { // Encrypt
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print("OTP file name to use (without extension) : ")
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val keyFile = readLine()!! + ".1tp"
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val kf = File(keyFile)
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if (kf.exists()) {
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val lines = File(keyFile).readLines().toMutableList()
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var first = lines.size
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for (i in 0 until lines.size) {
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if (lines[i].startsWith(" ")) {
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first = i
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break
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}
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}
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if (first == lines.size) {
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println("\nThat file has no unused lines.")
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continue@mainLoop
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}
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val lines2 = lines.drop(first) // get rid of comments and used lines
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println("Text to encrypt :-\n")
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val text = readLine()!!.toUpperCase().toAlpha()
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val len = text.length
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var nLines = len / CHARS_PER_LINE
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if (len % CHARS_PER_LINE > 0) nLines++
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if (lines2.size >= nLines) {
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val key = lines2.take(nLines).joinToString("").toAlpha()
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val encrypted = vigenere(text, key)
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val encFile = keyFile + "_enc"
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File(encFile).writeText(encrypted)
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println("\n'$encFile' has been created in the current directory.")
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for (i in first until first + nLines) {
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lines[i] = "-" + lines[i].drop(1)
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}
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File(keyFile).writeText(lines.joinToString("\n"))
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if (DEMO) {
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println("\nThe contents of the encrypted file are :\n")
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println(encrypted)
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}
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}
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else println("Not enough lines left in that file to do encryption")
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}
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else println("\nThat file does not exist.")
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}
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5 -> { // Decrypt
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print("OTP file name to use (without extension) : ")
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val keyFile = readLine()!! + ".1tp_cpy"
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val kf = File(keyFile)
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if (kf.exists()) {
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val keyLines = File(keyFile).readLines().toMutableList()
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var first = keyLines.size
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for (i in 0 until keyLines.size) {
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if (keyLines[i].startsWith(" ")) {
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first = i
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break
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}
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}
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if (first == keyLines.size) {
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println("\nThat file has no unused lines.")
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continue@mainLoop
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}
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val keyLines2 = keyLines.drop(first) // get rid of comments and used lines
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val encFile = keyFile.dropLast(3) + "enc"
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val ef = File(encFile)
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if (ef.exists()) {
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val encLines = File(encFile).readLines().drop(1) // exclude comment line
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val nLines = encLines.size
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if (keyLines2.size >= nLines) {
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val encrypted = encLines.joinToString("").toAlpha()
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val key = keyLines2.take(nLines).joinToString("").toAlpha()
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val decrypted = vigenere(encrypted, key, false)
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val decFile = keyFile.dropLast(3) + "dec"
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File(decFile).writeText(decrypted)
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println("\n'$decFile' has been created in the current directory.")
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for (i in first until first + nLines) {
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keyLines[i] = "-" + keyLines[i].drop(1)
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}
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File(keyFile).writeText(keyLines.joinToString("\n"))
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if (DEMO) {
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println("\nThe contents of the decrypted file are :\n")
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println(decrypted)
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}
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}
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else println("Not enough lines left in that file to do decryption")
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}
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else println("\n'$encFile' is missing.")
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}
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else println("\nThat file does not exist.")
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}
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else -> return // Quit
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}
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}
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}
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