simplest way to have cipher encryption in Kotlin

encryption.kt

import java.util.*
import javax.crypto.Cipher.*
import javax.crypto.spec.IvParameterSpec
import javax.crypto.spec.SecretKeySpec

fun main() {
  val str = "Hello World !"
  val encryptionKey = "1mfNnQ8CSdxHOhwO"
  println(str)
  val encoded = encrypt(str, encryptionKey)
  println(encoded)
  val decoded = decrypt(encoded, encryptionKey)
  println(decoded)
}

const val ALGO = "AES"
const val TRANSFORMATION = "AES/CBC/PKCS5Padding"

fun encrypt(input: String, encryptionKey: String): String {
  val secretKeySpec = SecretKeySpec(encryptionKey.toByteArray(), ALGO)
  val ivParameterSpec = IvParameterSpec(encryptionKey.toByteArray())
  val cipher = getInstance(TRANSFORMATION)!!
  cipher.init(ENCRYPT_MODE, secretKeySpec, ivParameterSpec)
  return Base64.getEncoder().encodeToString(cipher.doFinal(input.toByteArray()))
}

fun decrypt(input: String, encryptionKey: String): String {
  val secretKeySpec = SecretKeySpec(encryptionKey.toByteArray(), ALGO)
  val ivParameterSpec = IvParameterSpec(encryptionKey.toByteArray())
  val cipher = getInstance(TRANSFORMATION)!!
  cipher.init(DECRYPT_MODE, secretKeySpec, ivParameterSpec)
  val decodedValue = Base64.getDecoder().decode(input)!!
  return String(cipher.doFinal(decodedValue)!!)
}