Encrypt/Decrypt String Kotlin

问题

I've created this two extensions in Kotlin to Encrypt/Decrypt strings:

fun String.encrypt(seed : String): String {
    val keyGenerator = KeyGenerator.getInstance("AES")
    val secureRandom = SecureRandom.getInstance("SHA1PRNG")
    secureRandom.setSeed(seed.toByteArray())

    keyGenerator.init(128, secureRandom)
    val skey = keyGenerator.generateKey()
    val rawKey : ByteArray = skey.encoded

    val skeySpec = SecretKeySpec(rawKey, "AES")
    val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec)
    val byteArray = cipher.doFinal(this.toByteArray())

    return byteArray.toString()
}

fun String.decrypt(seed : String): String {
    val keyGenerator = KeyGenerator.getInstance("AES")
    val secureRandom = SecureRandom.getInstance("SHA1PRNG")
    secureRandom.setSeed(seed.toByteArray())

    keyGenerator.init(128, secureRandom)
    val skey = keyGenerator.generateKey()
    val rawKey : ByteArray = skey.encoded

    val skeySpec = SecretKeySpec(rawKey, "AES")
    val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
    cipher.init(Cipher.DECRYPT_MODE, skeySpec)
    val byteArray = cipher.doFinal(this.toByteArray())

    return byteArray.toString()
}

for some reason I'm getting the following exception:

javax.crypto.IllegalBlockSizeException: last block incomplete in decryption

What I'm doing wrong?

回答1:

To encode your ciphertext use base 64 or hexadecimals. The Java API contains a Base64 class, so you're probably best off using that.

byte[]#toString doesn't do what you expect it to do; it simply returns a representation of the byte array reference, not the contents of the byte array.

---

Besides that:

• don't use SecureRandom to derive a key, try and lookup PBKDF2;
• explicitly use a mode of operation such as "AES/GCM/NoPadding";
• use a unique IV, and a random IV if you decide to use CBC (usually insecure);
• don't use toByteArray without explicitly selecting a character encoding for the message.

回答2:

Following Maarten Bodews guides I fix the issues as:

fun String.encrypt(password: String): String {
    val secretKeySpec = SecretKeySpec(password.toByteArray(), "AES")
    val iv = ByteArray(16)
    val charArray = password.toCharArray()
    for (i in 0 until charArray.size){
        iv[i] = charArray[i].toByte()
    }
    val ivParameterSpec = IvParameterSpec(iv)

    val cipher = Cipher.getInstance("AES/GCM/NoPadding")
    cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec)

    val encryptedValue = cipher.doFinal(this.toByteArray())
    return Base64.encodeToString(encryptedValue, Base64.DEFAULT)
}

fun String.decrypt(password: String): String {
    val secretKeySpec = SecretKeySpec(password.toByteArray(), "AES")
    val iv = ByteArray(16)
    val charArray = password.toCharArray()
    for (i in 0 until charArray.size){
        iv[i] = charArray[i].toByte()
    }
    val ivParameterSpec = IvParameterSpec(iv)

    val cipher = Cipher.getInstance("AES/GCM/NoPadding")
    cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec)

    val decryptedByteValue = cipher.doFinal(Base64.decode(this, Base64.DEFAULT))
    return String(decryptedByteValue)
}

回答3:

AES Encryption / Decryption using base64 key, salt and iv (Initialization Vector).

object AESEncyption {

const val secretKey = "tK5UTui+DPh8lIlBxya5XVsmeDCoUl6vHhdIESMB6sQ="
const val salt = "QWlGNHNhMTJTQWZ2bGhpV3U=" // base64 decode => AiF4sa12SAfvlhiWu
const val iv = "bVQzNFNhRkQ1Njc4UUFaWA==" // base64 decode => mT34SaFD5678QAZX

fun encrypt(strToEncrypt: String) :  String?
{
    try
    {
        val ivParameterSpec = IvParameterSpec(Base64.decode(iv, Base64.DEFAULT))

        val factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
        val spec =  PBEKeySpec(secretKey.toCharArray(), Base64.decode(salt, Base64.DEFAULT), 10000, 256)
        val tmp = factory.generateSecret(spec)
        val secretKey =  SecretKeySpec(tmp.encoded, "AES")

        val cipher = Cipher.getInstance("AES/CBC/PKCS7Padding")
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivParameterSpec)
        return Base64.encodeToString(cipher.doFinal(strToEncrypt.toByteArray(Charsets.UTF_8)), Base64.DEFAULT)
    }
    catch (e: Exception)
    {
        println("Error while encrypting: $e")
    }
    return null
}

fun decrypt(strToDecrypt : String) : String? {
    try
    {

        val ivParameterSpec =  IvParameterSpec(Base64.decode(iv, Base64.DEFAULT))

        val factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
        val spec =  PBEKeySpec(secretKey.toCharArray(), Base64.decode(salt, Base64.DEFAULT), 10000, 256)
        val tmp = factory.generateSecret(spec);
        val secretKey =  SecretKeySpec(tmp.encoded, "AES")

        val cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretKey, ivParameterSpec);
        return  String(cipher.doFinal(Base64.decode(strToDecrypt, Base64.DEFAULT)))
    }
    catch (e : Exception) {
        println("Error while decrypting: $e");
    }
    return null
  }
}

iOS swift

回答4:

Following MarcForn guide I reduce it like this this:

const val encryptionKey = "ENCRYPTION_KEY"

fun String.cipherEncrypt(encryptionKey: String): String? {
    try {
        val secretKeySpec = SecretKeySpec(encryptionKey.toByteArray(), "AES")
        val iv = encryptionKey.toByteArray()
        val ivParameterSpec = IvParameterSpec(iv)

        val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec)

        val encryptedValue = cipher.doFinal(this.toByteArray())
        return Base64.encodeToString(encryptedValue, Base64.DEFAULT)
    } catch (e: Exception) {
        e.message?.let{ Log.e("encryptor", it) }
    }
    return null
}

fun String.cipherDecrypt(encryptionKey: String): String? {
    try {
        val secretKeySpec = SecretKeySpec(encryptionKey.toByteArray(), "AES")
        val iv = encryptionKey.toByteArray()
        val ivParameterSpec = IvParameterSpec(iv)

        val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec)

        val decodedValue = Base64.decode(this, Base64.DEFAULT)
        val decryptedValue = cipher.doFinal(decodedValue)
        return String(decryptedValue)
    } catch (e: Exception) {
        e.message?.let{ Log.e("decryptor", it) }
    }
    return null
}

来源：https://stackoverflow.com/questions/49340005/encrypt-decrypt-string-kotlin