AES/GCM/NoPadding Encryption Swift iOS

Currently I have been doing AES with CBC mode encryption but as backend change in requirement we have to change to to GCM mode with random IV generation .

currently I have this code :

Code Block 
 static func encryptsData(parameters: parameters?) -> (String, String) {
 var jsonStr = DefaultValues.empty
        do {
            if let str = String(data: try JSONSerialization.data(withJSONObject: parameters ?? [:], options: .prettyPrinted), encoding: .utf8) {
                jsonStr = str
            }
        } catch {
            debugPrint(error.localizedDescription)
        }
        // Get Secrete key, iv of 128 bits
        let iv = [UInt8](repeating: 0, count: 16)
        let randomStr = randomString(length: 16)
        let key: Array<UInt8> = Array(randomStr.utf8)
        // Encrypt Request Data with Secrete Key (AES)
        let aes =  try! AES(key: key, blockMode: CBC(iv: iv), padding: .pkcs5)
        let encrypted = try? aes.encrypt(Array(jsonStr.utf8))
             if let encryptedMsg = encrypted {
            let encryptedData =  Data(bytes: encryptedMsg, count: Int(encryptedMsg.count))
            let encryptedBase64 = encryptedData.base64EncodedString()
            //Encrypt Secrete Key using Server Public key (RSA)
            let keyData = Data(bytes: key, count: key.count)
            let encryptedSceKey = encryptSecKeyWithPublickKey(key: String(data: keyData, encoding: .utf8) ?? "")
            return (encryptedBase64, encryptedSceKey)
        }
        return (DefaultValues.empty, DefaultValues.empty)
}

  Now , have changed the code for GCM Mode in the following lines :

Code Block 
  let iv = AES.randomIV(AES.blockSize) //[UInt8](repeating: 0, count: 16)
        var bytes = [Int8](repeating: 0, count: 16)
         let randomStr = randomString(length:16)
        let key: Array<UInt8> = Array(randomStr.utf8)
        // Encrypt Request Data with Secrete Key (AES)
        let aes =  try! AES(key: key, blockMode: GCM(iv: iv), padding: .noPadding)

else , remaining the same..But could get success through this as our encryption has to be in sync with the android/java side.

On Android end this is the encryption code :

Code Block lpackage com.jio.ngo.datalayer.network.encryption
import android.util.Base64
import android.util.Log
import com.jio.ngo.datalayer.BuildConfig
import java.nio.charset.Charset
import java.security.*
import java.security.spec.InvalidKeySpecException
import java.security.spec.X509EncodedKeySpec
import javax.crypto.*
import javax.crypto.spec.GCMParameterSpec
import javax.crypto.spec.SecretKeySpec
object Encryption
{
    val TAG = "Encryption"
    private const val GCM_IV_LENGTH = 12
    fun encrypt(message: String): EncryptedRequest
    {
        val encryptedRequest = EncryptedRequest()
        try
        {
            // 1. generate secret key using AES
            val keyGenerator = KeyGenerator.getInstance("AES")
            keyGenerator.init(256)
            // AES is currently available in three key sizes: 128, 192 and 256 bits.The
            // design and strength of all key lengths of the AES algorithm are sufficient to
            // protect classified information up to the SECRET level
            val secretKey = keyGenerator.generateKey()
            // 2. get string which needs to be encrypted
            // 3. encrypt string using secret key
            val raw = secretKey.encoded
            val skeySpec = SecretKeySpec(raw, "AES")
//            val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
            val cipher = Cipher.getInstance("AES/GCM/NoPadding")
            val iv = ByteArray(GCM_IV_LENGTH)
            SecureRandom().nextBytes(iv)
            val parameterSpec = GCMParameterSpec(128, iv) //128
//            val parameterSpec: GCMParameterSpec = cipher.parameters.getParameterSpec(GCMParameterSpec::class.java)
//            cipher.init(Cipher.ENCRYPT_MODE, skeySpec, IvParameterSpec(ByteArray(16)))
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec, parameterSpec)
            val encryptedMessageBytes: ByteArray = cipher.doFinal(message.toByteArray(Charset.forName("UTF-8")))
            val encrypted = ByteArray(iv.size + encryptedMessageBytes.size)
            System.arraycopy(iv, 0, encrypted, 0, iv.size)
            System.arraycopy(encryptedMessageBytes, 0, encrypted, iv.size, encryptedMessageBytes.size)
            val cipherTextString = Base64.encodeToString(encrypted, Base64.DEFAULT)
            Log.d(TAG, "cipherTextString : $cipherTextString")
            Log.d(TAG, "cipherTextString 1: ${Base64.encodeToString(skeySpec.encoded, Base64.DEFAULT)}")
            // 4. get public key
            val publicSpec = X509EncodedKeySpec(Base64.decode(BuildConfig.apikey, Base64.DEFAULT))
            val keyFactory = KeyFactory.getInstance("RSA")
            val publicKey = keyFactory.generatePublic(publicSpec)
            // 6. encrypt secret key using public key
            val cipher2 = Cipher.getInstance("RSA/ECB/OAEPWithSHA1AndMGF1Padding")
            cipher2.init(Cipher.ENCRYPT_MODE, publicKey)
            val encryptedSecretKey = Base64.encodeToString(cipher2.doFinal(secretKey.encoded), Base64.DEFAULT)
            //System.out.println(encryptedSecretKey);
            Log.d(TAG, "encryptedSecretKey : $encryptedSecretKey")
            // 7. pass cipherTextString (encypted sensitive data) and encryptedSecretKey to
            // your server via your preferred way.
            // Tips:
            // You may use JSON to combine both the strings under 1 object.
            // You may use a volley call to send this data to your server.
            encryptedRequest.encryptedText = cipherTextString
            encryptedRequest.encryptedSecretKeyString = encryptedSecretKey
        } catch (e: NoSuchAlgorithmException) {
            e.printStackTrace()
        } catch (e: InvalidKeyException) {
            e.printStackTrace()
        } catch (e: NoSuchPaddingException) {
            e.printStackTrace()
        } catch (e: IllegalBlockSizeException) {
            e.printStackTrace()
        } catch (e: BadPaddingException) {
            e.printStackTrace()
        } catch (e: InvalidKeySpecException) {
            e.printStackTrace()
        } catch (e: InvalidAlgorithmParameterException) {
            e.printStackTrace()
        }
        catch (e: Exception)
        {
            e.printStackTrace()
        }
        return encryptedRequest
    }
}

So, have to find way around like what Java end encryption is happening , not able to get what is the issue at our end.

failing decrypting in backend when using above iOS encryption code :

Code Block 
 javax.crypto.AEADBadTagException: Tag mismatch!

Please help ....
Thanks !!