package tool.security;

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
 * @author Alexis Caron
 * Objet d'encryption de donnee
 */
public class AES { 
	private final static String HEX = "0123456789ABCDEF";
	
	/**
	 * @param seed
	 * @param cleartext
	 * @return String encrypter
	 * @throws Exception
	 */
	public static String encrypt(String seed, String cleartext) throws Exception 
	{ 
		byte[] rawKey = getRawKey(seed.getBytes()); 
		byte[] result = encrypt(rawKey, cleartext.getBytes()); 
		return toHex(result); 
	} 
	
	/**
	 * @param seed
	 * @return byte[] de la cle pour encrypter
	 * @throws Exception
	 */
	private static byte[] getRawKey(byte[] seed) throws Exception 
	{ 
		KeyGenerator kgen = KeyGenerator.getInstance("AES"); 
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); 
		sr.setSeed(seed); 
		kgen.init(128, sr); // 192 and 256 bits may not be available 
		SecretKey skey = kgen.generateKey(); 
		byte[] raw = skey.getEncoded(); 
		return raw; 
	} 
	
	/**
	 * @param raw
	 * @param clear
	 * @return byte[] de la string encrypter
	 * @throws Exception
	 */
	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception 
	{ 
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); 
		Cipher cipher = Cipher.getInstance("AES"); 
		cipher.init(Cipher.ENCRYPT_MODE, skeySpec); 
		byte[] encrypted = cipher.doFinal(clear); 
		return encrypted; 
	} 
	
	/**
	 * @param txt
	 * @return String en hexadecimal
	 */
	public static String toHex(String txt) 
	{ 
		return toHex(txt.getBytes()); 
	} 
	
	/**
	 * @param hex
	 * @return String en ascii
	 */
	public static String fromHex(String hex) 
	{ 
		return new String(toByte(hex)); 
	} 
	
	/**
	 * @param hexString
	 * @return byte[] de la string
	 */
	public static byte[] toByte(String hexString) 
	{ 
		int len = hexString.length()/2; 
		byte[] result = new byte[len]; 
		for (int i = 0; i < len; i++) 
			result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
		return result;
	} 
	
	/**
	 * @param buf
	 * @return String en hexadecimal
	 */
	public static String toHex(byte[] buf) 
	{ 
		if (buf == null) return "";
		StringBuffer result = new StringBuffer(2*buf.length); 
		for (int i = 0; i < buf.length; i++) 
		{ 
			appendHex(result, buf[i]); 
		} 
		return result.toString(); 
	} 
	
	/**
	 * @param sb
	 * @param b
	 */
	private static void appendHex(StringBuffer sb, byte b) 
	{ 
		sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f)); 
	}
	
	public static void main(String[] args) throws Exception {
		String password = "banane32",
		       secretKey = "804464551E45D45E76A25D76322FBFC3804464551E45D45E76A25D76322FBFC3",
		       encrypted = AES.encrypt(secretKey,password);
		System.out.println("after encryption " + encrypted);
	}
}