please share how to string encrypt / decryption?

[Winanjaya]

Hello All,

Could any body please share how to string encrypt / decryption?

thanks a lot in advance

Regards

[ComputerJy]

Here is a sample. If this is your first time you need to do a whole lot of reading

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class Test {

	public static void main(final String[] args) throws Exception {
		final byte[] input = "Hello World!".getBytes();
		final byte[] keyBytes = new byte[]{0x01, 0x23, 0x45, 0x67, (byte) 0x89, (byte) 0xab, (byte) 0xcd,
			(byte) 0xef, 0x14, 0x9, 0x12, 0x34, 0x01, 0x23, 0x45, 0x67, (byte) 0x89, (byte) 0xab, (byte) 0xcd,
			(byte) 0xef, 0x14, 0x9, 0x12, 0x34};

		final SecretKeySpec key = new SecretKeySpec(keyBytes, "DESede");
		final Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
		System.out.println("input : " + new String(input));

		// encrypt message
		cipher.init(Cipher.ENCRYPT_MODE, key);
		final byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
		int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
		ctLength += cipher.doFinal(cipherText, ctLength);
		System.out.println("cipher: " + new String(cipherText) + " bytes: " + ctLength);

		// decrypt message
		cipher.init(Cipher.DECRYPT_MODE, key);
		final byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
		int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
		ptLength += cipher.doFinal(plainText, ptLength);
		System.out.println("plain : " + new String(plainText) + " bytes: " + ptLength);
	}
}

[Winanjaya]

Hi .. but it's become more complex if I separated encrypt & decrypt into 2 method.. any idea?

[ComputerJy]

Ok, here is another sample using the XTea algorithm:

public class Test
{
	public static void main(final String[] args) throws Exception
	{
		final String str = "Hello World!";
		final String key = "password";
		final String encryptedString = encrypt(str, key);
		System.out.println(encryptedString);
		final String decryptedString = decrypt(encryptedString, key);
		System.out.println(decryptedString);
	}

	public static String encrypt(String data, final String key) throws Exception
	{
		if (data.length() == 0)
			throw new Exception("Data must be at least 1 character in length.");

		final long[] formattedKey = formatKey(key);

		if (data.getBytes().length % 2 != 0)
			data += '\0';

		final byte[] dataBytes = data.getBytes();
		String cipher = "";
		final int[] tempData = new int[2];

		for (int i = 0; i < dataBytes.length; i += 2)
		{
			tempData[0] = dataBytes[i];
			tempData[1] = dataBytes[i + 1];
			code(tempData, formattedKey);
			cipher += convertUIntToString(tempData[0]) + convertUIntToString(tempData[1]);
		}

		return cipher;
	}

	public static String decrypt(final String data, final String key) throws Exception
	{
		final long[] formattedKey = formatKey(key);
		int x = 0;
		final int[] tempData = new int[2];
		final byte[] dataBytes = new byte[data.length() / 8 * 2];

		for (int i = 0; i < data.length(); i += 8)
		{
			tempData[0] = convertStringToUInt(data.substring(i, i + 4));
			tempData[1] = convertStringToUInt(data.substring(i + 4, i + 8));
			decode(tempData, formattedKey);
			dataBytes[x++] = (byte) tempData[0];
			dataBytes[x++] = (byte) tempData[1];
		}

		String decipheredString = new String(dataBytes, 0, dataBytes.length);

		if (decipheredString.charAt(decipheredString.length() - 1) == '\0')
			decipheredString = decipheredString.substring(0, decipheredString.length() - 1);

		return decipheredString;
	}

	private static void code(final int[] v, final long[] k)
	{
		int y = v[0];
		int z = v[1];
		int sum = 0;
		final int delta = 0x9E3779B9;
		int n = 32;

		while (n-- > 0)
		{
			y += ((z << 4 ^ z >>> 5) + z) ^ (sum + k[sum & 3]);
			sum += delta;
			z += ((y << 4 ^ y >>> 5) + y) ^ (sum + k[sum >> 11 & 3]);
		}

		v[0] = y;
		v[1] = z;
	}

	private static void decode(final int[] tempData, final long[] k)
	{
		int y = tempData[0];
		int z = tempData[1];
		int sum = 0xC6EF3720;
		final int delta = 0x9E3779B9;
		int n = 32;

		while (n-- > 0)
		{
			z -= ((y << 4 ^ y >>> 5) + y) ^ (sum + k[sum >> 11 & 3]);
			sum -= delta;
			y -= ((z << 4 ^ z >>> 5) + z) ^ (sum + k[sum & 3]);
		}

		tempData[0] = y;
		tempData[1] = z;
	}

	private static String convertUIntToString(final int Input)
	{
		final StringBuilder output = new StringBuilder();
		output.append((char) ((Input & 0xFF)));
		output.append((char) ((Input >> 8) & 0xFF));
		output.append((char) ((Input >> 16) & 0xFF));
		output.append((char) ((Input >> 24) & 0xFF));
		return output.toString();
	}

	private static int convertStringToUInt(final String Input)
	{
		int output;
		output = Input.charAt(0);
		output += (Input.charAt(1) << 8);
		output += (Input.charAt(2) << 16);
		output += (Input.charAt(3) << 24);
		return output;
	}

	private static long[] formatKey(String Key) throws Exception
	{
		if (Key.length() == 0)
			throw new Exception("Key must be between 1 and 16 characters in length");
		while (Key.length() < 16)
			Key += "a";

		Key = Key.substring(0, 16);

		final long[] formattedKey = new long[4];

		// Get the key into the correct format for TEA usage.
		int j = 0;

		for (int i = 0; i < Key.length(); i += 4)
			formattedKey[j++] = convertStringToUInt(Key.substring(i, i + 4));

		return formattedKey;
	}
}

[Winanjaya]

Thanks a lot ..