import java.io.ObjectInputStream.GetField;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;

public class AESCrypt {

	private final Cipher cipher;
	private final SecretKeySpec key;
	private String encryptedText, decryptedText;
	//private AlgorithmParameterSpec ivspec;

	public AESCrypt(String password) throws Exception {
		// hash password with SHA-256 and crop the output to 128-bit for key
		MessageDigest digest = MessageDigest.getInstance("SHA-256");
		digest.update(password.getBytes("UTF-8"));
		byte[] keyBytes = new byte[16];
		System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);

		cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
		key = new SecretKeySpec(keyBytes, "AES");
		//byte[] iv = new byte[cipher.getBlockSize()];
		//ivspec = new IvParameterSpec(iv);
		getIV();
	}
	
	public AlgorithmParameterSpec getIV() {
		AlgorithmParameterSpec ivspec;
		byte[] iv = new byte[cipher.getBlockSize()];
		new SecureRandom().nextBytes(iv);
		ivspec = new IvParameterSpec(iv);
		return ivspec;
		}

	public String encrypt(String plainText) throws Exception {
		
		cipher.init(Cipher.ENCRYPT_MODE, key, getIV());
		byte[] encrypted = cipher.doFinal(plainText.getBytes());
		encryptedText = DatatypeConverter.printBase64Binary(encrypted);
		return encryptedText;
	}

	public String decrypt(String cryptedText) throws Exception {
		cipher.init(Cipher.DECRYPT_MODE, key, getIV());
		byte[] bytes = DatatypeConverter.parseBase64Binary(cryptedText);
		byte[] decrypted = cipher.doFinal(bytes);
		decryptedText = new String(decrypted, "UTF-8");
		return decryptedText;
	}	

	public static void main(String[] args) throws Exception {

		System.out.print("....AES....\n");

		String message = "DOBOJ";
		String password = "PASSWORD";

		System.out.println("MSG:" + message);

		AESCrypt aes = new AESCrypt(password);
		String encryptedText = aes.encrypt(message).toString();
		System.out.println("ENCRYPTED MSG: " + encryptedText);
		String decryptedText = aes.decrypt(encryptedText);
		System.out.print("DECRYPTED MSG: " + decryptedText);
	}

}