MD5实现加密解密

import java.security.MessageDigest;

public class MD5Util {
	
	// MD5加密。32位的。
	public static String md5ToSecret(String source) {
		MessageDigest md5 = null;
		try {
			md5 = MessageDigest.getInstance("MD5");
		} catch (Exception e) {
			System.out.println(e.toString());
			e.printStackTrace();
			return "";
		}
		char[] charArray = source.toCharArray();
		byte[] byteArray = new byte[charArray.length];

		for (int i = 0; i < charArray.length; i++)
			byteArray[i] = (byte) charArray[i];

		byte[] md5Bytes = md5.digest(byteArray);

		StringBuffer hexValue = new StringBuffer();

		for (int i = 0; i < md5Bytes.length; i++) {
			int val = ((int) md5Bytes[i]) & 0xff;
			if (val < 16)
				hexValue.append("0");
			hexValue.append(Integer.toHexString(val));
		}
		return hexValue.toString();
	}

	// 可逆的加密算法
	public static String md5Encrypt(String inStr) {
		// String s = new String(inStr);
		char[] a = inStr.toCharArray();
		for (int i = 0; i < a.length; i++) {
			a[i] = (char) (a[i] ^ 't');
		}
		String s = new String(a);
		return s;
	}

	// 加密后解密
	public static String md5Decrypt(String inStr) {
		char[] a = inStr.toCharArray();
		for (int i = 0; i < a.length; i++) {
			a[i] = (char) (a[i] ^ 't');
		}
		String k = new String(a);
		return k;
	}

	
	public static void main(String[] args) {
		String s = "123456";
		System.out.println("原字符串："  + s);
		System.out.println("MD5加密之后："  + md5ToSecret(s));
		System.out.println("再加密："  + md5Encrypt(md5ToSecret(s)));
		System.out.println("解密之后："  + md5Decrypt(md5Encrypt(md5ToSecret(s))));
	}
}