AES/GCM/NoPadding in swift iOS - bouncycastle

Question

I want to implement AES GCM encryption/decryption using shared secret.
But Backend server is throwing error with my keys. This is working fine in Android app with Java. Although size of encrypted text is same in both iOS and Android.
My iOS code.
private func getCryptoPublicKey() -> (privateKey: Curve25519.KeyAgreement.PrivateKey,publicKey :Curve25519.KeyAgreement.PublicKey){
let ephemeralKey = Curve25519.KeyAgreement.PrivateKey()
//AES.KeyWrap.wrap(SymmetricKey(size: .bits256), using: <#T##SymmetricKey#>)
let ephemeralPublicKey = ephemeralKey.publicKey
let privateKey = ephemeralKey.rawRepresentation.base64EncodedString()
let publicKey = ephemeralPublicKey.rawRepresentation.base64EncodedString()
Singleton.shared.clientPrivateKey = privateKey
Singleton.shared.clientPublicKey = publicKey
return (ephemeralKey,ephemeralPublicKey)
}
let cryptoData = self.getCryptoPublicKey()
let publicKeyData = Data.init(base64Encoded: ServerPublicKey)! //ServerPublicKey is shared by server
let serverPublicKey = try! Curve25519.KeyAgreement.PublicKey(rawRepresentation: publicKeyData)
let clientSharedSecret = try! cryptoData.privateKey.sharedSecretFromKeyAgreement(with: serverPublicKey)
let clientSharedSecretSymmetricKey = clientSharedSecret.x963DerivedSymmetricKey(using: SHA256.self, sharedInfo: Data(), outputByteCount: 32)
let clientSealedBoxDatakClientId = try! AES.GCM.seal(kClientId.data(using: .utf8)!, using: clientSharedSecretSymmetricKey).combined!
let clientSealedBoxDatakClientSecret = try! AES.GCM.seal(kClientSecret.data(using: .utf8)!, using: clientSharedSecretSymmetricKey).combined!
let clientSealedBoxDataCredent = try! AES.GCM.seal("client_credentials".data(using: .utf8)!, using: clientSharedSecretSymmetricKey).combined!
let clientIDEncryptedBase64Str = clientSealedBoxDatakClientId.base64EncodedString()
let clientSecretEncryptedBase64Str = clientSealedBoxDatakClientSecret.base64EncodedString()
let clientCredentialsEncryptedBase64Str = clientSealedBoxDataCredent.base64EncodedString()
JAVA CODE:
`
private void makeKeyExchangeParams() {
KeyPairGenerator kpg;
try {
kpg = KeyPairGenerator.getInstance("X25519", new org.bouncycastle.jce.provider.BouncyCastleProvider());
kpg.initialize(AES_KEY_SIZE);
KeyPair kp = kpg.generateKeyPair();
publickey = kp.getPublic();
keyAgreement = KeyAgreement.getInstance("XDH", new org.bouncycastle.jce.provider.BouncyCastleProvider());
keyAgreement.init(kp.getPrivate());
} catch (NoSuchAlgorithmException | InvalidKeyException e) {
e.printStackTrace();
}
}
package com.bankofbaroda.bobabhivyakti.Utilities.Encryption;
import android.os.Build;
import androidx.annotation.RequiresApi;
import javax.crypto.*;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.util.Base64;
public class CryptoService {
public static final int GCM_IV_LENGTH = 12;
public static final int GCM_TAG_LENGTH = 16;
#RequiresApi(api = Build.VERSION_CODES.O)
public static String getEncryptedText(String plainText, SecretKey secretKey) {
if(plainText == null) {
plainText = "";
}
try {
byte[] ivBytes = new byte[GCM_IV_LENGTH];
SecureRandom random = new SecureRandom();
random.nextBytes(ivBytes);
String iv = Base64.getEncoder().encodeToString(ivBytes);
byte[] cipherText = encrypt(plainText.getBytes(), secretKey, ivBytes);
String text = Base64.getEncoder().encodeToString(cipherText);
text = iv+text;
return text;
} catch (Exception e) {
e.printStackTrace();
return "";
}
}
#RequiresApi(api = Build.VERSION_CODES.O)
public static String getDecryptedText(String cipherText, SecretKey secretKey) {
try {
String iv = cipherText.substring(0,16);
byte[] ivBytes = Base64.getDecoder().decode(iv);
cipherText = cipherText.substring(16);
byte[] data = Base64.getDecoder().decode(cipherText);
return decrypt(data, secretKey, ivBytes);
} catch (Exception e) {
e.printStackTrace();
return "";
}
}
private static byte[] encrypt(byte[] plaintext, SecretKey key, byte[] nonce) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "AES");
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, nonce);
cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmParameterSpec);
return cipher.doFinal(plaintext);
}
private static String decrypt(byte[] cipherText, SecretKey key, byte[] nonce) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "AES");
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, nonce);
cipher.init(Cipher.DECRYPT_MODE, keySpec, gcmParameterSpec);
byte[] decryptedText = cipher.doFinal(cipherText);
return new String(decryptedText);
}
}
`
I am not able to get what is exact issue here. Do I have to change something on Java side?