// Encryption, client side

byte[] plainData = "hello plaintext!".getBytes("UTF-8");

byte[] salt = new byte[64];

new SecureRandom().nextBytes(salt);

KeySpec spec = new javax.crypto.spec.PBEKeySpec("password".toCharArray(), salt, 1024, 256);

SecretKey sk = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1").generateSecret(spec);

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(sk.getEncoded(), "AES"));

byte[] iv = cipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();

byte[] ciphertext = cipher.doFinal(plainData);

System.out.println("ciphertext: "+new String(ciphertext, "UTF-8")); // cipher

// Decryption, server side

KeySpec spec2 = new javax.crypto.spec.PBEKeySpec("password".toCharArray(), salt, 1024, 256);

SecretKey sk2 = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1").generateSecret(spec2);

Cipher cipher2 = Cipher.getInstance("AES/CBC/PKCS5Padding");

cipher2.init(Cipher.DECRYPT_MODE, new SecretKeySpec(sk2.getEncoded(), "AES"), new IvParameterSpec(iv)); // Get the same IV value from client/encryptor aswell, still random

String plaintext = new String(cipher2.doFinal(ciphertext), "UTF-8");

System.out.println("decrypted plaintext: "+plaintext); // plain

I can see that you are creating a different salt at the client and server side.

In order for the server side to be able to decrypt that salt and the key have to be the same.

Now I'm not a Java developer but all the other code to me looks ok but

like I said if you are creating a different salt at each end the decryption is not going to work.

Looks like I have to send over the same IV value to the server aswell