import javax.crypto.Cipher
import javax.crypto.SecretKey
import javax.crypto.SecretKeyFactory
import javax.crypto.spec.DESedeKeySpec

fun main() {
    // Replace the keyString with your 3DES key in hexadecimal format
    val keyString = "40021940DAAEF8EFC7BADF9BFBB501B640021940DAAEF8EF"

    try {
        // Convert hexadecimal string to byte array
        val keyBytes = hexStringToByteArray(keyString)

        // Create DESedeKeySpec from the byte array
        val keySpec = DESedeKeySpec(keyBytes)

        // Create DESede key using SecretKeyFactory
        val keyFactory = SecretKeyFactory.getInstance("DESede")
        val key: SecretKey = keyFactory.generateSecret(keySpec)

        // Calculate and print Key Check Value (KCV)
        val kcv = calculateKCV(key)
        println("Key Check Value (KCV): $kcv")
    } catch (e: Exception) {
        e.printStackTrace()
    }
}

// Function to convert hexadecimal string to byte array
fun hexStringToByteArray(hexString: String): ByteArray {
    return ByteArray(hexString.length / 2) {
        hexString.substring(it * 2, it * 2 + 2).toInt(16).toByte()
    }
}

// Function to convert byte array to hexadecimal string
fun byteArrayToHexString(bytes: ByteArray): String {
    return bytes.joinToString("") { "%02X".format(it) }
}

// Function to calculate Key Check Value (KCV) for 3DES key
fun calculateKCV(key: SecretKey): String {
    try {
        // Create a cipher with ECB mode and NoPadding
        val cipher = Cipher.getInstance("DESede/ECB/NoPadding")
        cipher.init(Cipher.ENCRYPT_MODE, key)

        // Encrypt a block of zeros and extract the first 8 hexadecimal characters
        val kcvBytes = cipher.doFinal(byteArrayOf(0, 0, 0, 0, 0, 0, 0, 0))
        val kcv = byteArrayToHexString(kcvBytes).substring(0, 16)
        println("Encrypted Zero Block: ${byteArrayToHexString(kcvBytes)}")
        return kcv
    } catch (e: Exception) {
        e.printStackTrace()
        return ""
    }
}

Kotlin online compiler

Write, Run & Share Kotlin code online using OneCompiler’s Kotlin online compiler for free. It’s a modern and fast online playground for Kotlin, supporting the latest version and ideal for learning, experimenting, and sharing code instantly.

About Kotlin

Kotlin is a statically typed, modern programming language developed by JetBrains. It runs on the JVM and is fully interoperable with Java. Kotlin is concise, expressive, and safe, and it’s officially supported by Google for Android app development.

Sample Code

The following is a simple Kotlin program that prints a greeting:

fun main() {
    println("Hello, OneCompiler!")
}

Taking inputs (stdin)

OneCompiler’s Kotlin editor supports stdin. You can provide input using the I/O tab. Here's a sample program that reads a line of input and prints a greeting:

fun main() {
    print("Enter your name: ")
    val name = readLine()
    println("Hello, $name")
}

Syntax Basics

Variables

val name: String = "OneCompiler"  // Immutable
var age: Int = 25                 // Mutable

Kotlin supports type inference, so explicit types are optional:

val city = "Hyderabad"
var count = 10

Conditionals

val score = 85
if (score >= 50) {
    println("Pass")
} else {
    println("Fail")
}

Loops

For loop

for (i in 1..5) {
    println(i)
}

While loop

var i = 1
while (i <= 5) {
    println(i)
    i++
}

Do-While loop

var j = 1
do {
    println(j)
    j++
} while (j <= 5)

Functions

fun add(a: Int, b: Int): Int {
    return a + b
}

fun greet(name: String) = "Hello, $name"

Collections

val items = listOf("apple", "banana", "cherry")
for (item in items) {
    println(item)
}

This guide provides a quick reference to Kotlin programming syntax and features. Start coding in Kotlin using OneCompiler’s Kotlin online compiler today!