[kotlin] 안드로이드 aes256 암호화 복호화

cbc 사용

PKCS5Padding:

fun encryptCBC(strToEncrypt: String, key: String, iv: String): String {

    try {

        val ivParameterSpec = IvParameterSpec(iv.toByteArray())
        val secretKey = SecretKeySpec(key.toByteArray(), "AES")

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

        val crypted = cipher.doFinal(strToEncrypt.toByteArray())
        val encodedByte = Base64.encode(crypted, Base64.DEFAULT)

        return String(encodedByte)

    } catch (e: Exception) {
        Log.e("Exception", "Exception : ${e.message}")
    }
    return ""
}

fun decryptCBC(strToDecrypt: String, key: String, iv: String): String {

    val ivParameterSpec = IvParameterSpec(iv.toByteArray())
    val secretKey = SecretKeySpec(key.toByteArray(), "AES")

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

    val decodedByte = Base64.decode(strToDecrypt, Base64.DEFAULT)
    val byteResult = cipher.doFinal(decodedByte)

    return String(byteResult)
}

PKCS7Padding:

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
    }
}

gcm 사용

fun 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 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)
}