A simple XOR cipher/encryption in kotlin :)

XORCryptor.kt

/*
 * Copyright (c) 2020, Shashank Verma <shashank.verma2002@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 */

/**
 * @author Shashank Verma
 *
 * XOR Cipher.
 * It can only decrypt with right keys ;)
 */
object XORCryptor {

    private fun generateMask(value: Int): Int {
        var mask = 0
        var prV = value
        while (prV != 0) {
            if (prV and 1 == 1) mask++
            prV = prV shr 1
        }
        mask = mask or ((8 - mask) shl 4)
        mask = mask xor ((mask shl 4) or (mask shr 4))
        return mask xor value
    }

    fun processBytes(srcBytes: ByteArray, keyBytes: ByteArray): ByteArray {
        var keyIdx = 0
        for (i in srcBytes.indices) {
            if (keyIdx == keyBytes.size) keyIdx = 0
            val b = srcBytes[i].toInt()
            val k = generateMask(keyBytes[keyIdx++].toInt())
            srcBytes[i] = b.xor(k).toByte()
        }
        return srcBytes
    }
}

// Usage:

fun main() {
    print("Enter text: ")
    val text = readLine()!!
    print("Enter key: ")
    val key = readLine()!!

    var data = String(XORCryptor.processBytes(text.toByteArray(), key.toByteArray()))
    println("Encrypted: $data")

    data = String(XORCryptor.processBytes(data.toByteArray(), key.toByteArray()))
    println("Decrypted: $data")
}