import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.spec.KeySpec;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import org.junit.Test;

public class JI9051435 {
	@Test 
	public void shouldBeThreadSafe() { 

		final byte[] encoded = { 
				27, 26, 18, 88, 84, -87, -40, -91, 70, -74, 87, -21, -124, 
				-114, -44, -24, 7, -7, 104, -26, 45, 96, 119, 45, -74, 51 
		}; 
		final String expected = "dummy data"; 
		final Charset charset = StandardCharsets.UTF_8; 

		final String salt = "e47312da-bc71-4bde-8183-5e25db6f0987"; 
		final String passphrase = "dummy-passphrase"; 

		// Crypto configuration 
		final int iterationCount = 10; 
		final int keyStrength = 128; 
		final String pbkdf2Algorithm = "PBKDF2WithHmacSHA1"; 
		final String cipherAlgorithm = "AES/CFB/NoPadding"; 
		final String keyAlgorithm = "AES"; 

		// Counters 
		final AtomicInteger succeedCount = new AtomicInteger(0); 
		final AtomicInteger failedCount = new AtomicInteger(0); 

		// Test 
		System.setProperty("java.util.concurrent.ForkJoinPool.common.parallelism", "10"); 
		IntStream.range(0, 1000000).parallel().forEach(i -> { 
			try { 

				SecretKeyFactory factory = SecretKeyFactory.getInstance(pbkdf2Algorithm); 
				KeySpec spec = new PBEKeySpec(passphrase.toCharArray(), salt.getBytes(charset), iterationCount, keyStrength); 
				SecretKey tmp = factory.generateSecret(spec); 
				SecretKeySpec key = new SecretKeySpec(tmp.getEncoded(), keyAlgorithm); 
				Cipher cipher = Cipher.getInstance(cipherAlgorithm); 


				int blockSize = cipher.getBlockSize(); 
				IvParameterSpec iv = new IvParameterSpec(Arrays.copyOf(encoded, blockSize)); 
				byte[] dataToDecrypt = Arrays.copyOfRange(encoded, blockSize, encoded.length); 
				cipher.init(Cipher.DECRYPT_MODE, key, iv); 
				byte[] utf8 = cipher.doFinal(dataToDecrypt); 

				String decoded = new String(utf8, charset); 
				if (!expected.equals(decoded)) { 
					System.out.println("Try #" + i + " | Unexpected decoded value: [" + decoded + "]"); 
					failedCount.incrementAndGet(); 
				} else { 
					succeedCount.incrementAndGet(); 
				} 
			} catch (Exception e) { 
				System.out.println("Try #" + i + " | Decode failed"); 
				e.printStackTrace(); 
				failedCount.incrementAndGet(); 
			} 
		}); 

		System.out.println(failedCount.get() + " of " + (succeedCount.get() + failedCount.get()) + " decodes failed"); 
	} 
}