Android kotlin encrypt decrypt example

extension.kt

lateinit var secretKey : SecretKey
lateinit var iv : ByteArray
fun encrypt(context:Context, strToEncrypt: String): ByteArray {
    val plainText = strToEncrypt.toByteArray(Charsets.UTF_8)
    val keygen = KeyGenerator.getInstance("AES")
    keygen.init(256)
    val key = keygen.generateKey()
    secretKey = key
    val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
    cipher.init(Cipher.ENCRYPT_MODE, key)
    val cipherText = cipher.doFinal(plainText)
    iv = cipher.iv

    val sb = StringBuilder()
    for (b in cipherText) {
        sb.append(b.toChar())
    }
    Toast.makeText(context, "dbg encrypted = [" + sb.toString() + "]", Toast.LENGTH_LONG).show()

    return cipherText
}

fun decrypt(context:Context, dataToDecrypt: ByteArray): ByteArray {
    val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
    val ivSpec = IvParameterSpec(iv)
    cipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec)
    val cipherText = cipher.doFinal(dataToDecrypt)

    val sb = StringBuilder()
    for (b in cipherText) {
        sb.append(b.toChar())
    }
    Toast.makeText(context, "dbg decrypted = [" + sb.toString() + "]", Toast.LENGTH_LONG).show()

    return cipherText
}