java md5加密

学习url：http://www.ibm.com/developerworks/cn/java/l-security/

MD5 16位加密

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class PasswordEnOrDecode {

	private static final String PASSWORD_CRYPT_KEY = "__longteng_";

	private final static String DES = "DES";

	/**
	 * 加密
	 * 
	 * @param src
	 *            数据源
	 * @param key
	 *            密钥，长度必须是8的倍数
	 * @return 返回加密后的数据
	 * @throws Exception
	 */

	public static byte[] encrypt(byte[] src, byte[] key) throws Exception {
		// DES算法要求有一个可信任的随机数源
		SecureRandom sr = new SecureRandom();
		// 从原始密匙数据创建DESKeySpec对象
		DESKeySpec dks = new DESKeySpec(key);
		// 创建一个密匙工厂，然后用它把DESKeySpec转换成
		// 一个SecretKey对象
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);

		SecretKey securekey = keyFactory.generateSecret(dks);

		// Cipher对象实际完成加密操作
		Cipher cipher = Cipher.getInstance(DES);

		// 用密匙初始化Cipher对象
		cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);

		// 现在，获取数据并加密

		// 正式执行加密操作
		return cipher.doFinal(src);

	}

	/**
	 * 解密
	 * 
	 * @param src
	 *            数据源
	 * @param key
	 *            密钥，长度必须是8的倍数
	 * @return 返回解密后的原始数据
	 * @throws Exception
	 * 
	 */

	public static byte[] decrypt(byte[] src, byte[] key) throws Exception {
		// DES算法要求有一个可信任的随机数源
		SecureRandom sr = new SecureRandom();
		// 从原始密匙数据创建一个DESKeySpec对象
		DESKeySpec dks = new DESKeySpec(key);
		// 创建一个密匙工厂，然后用它把DESKeySpec对象转换成
		// 一个SecretKey对象
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
		SecretKey securekey = keyFactory.generateSecret(dks);
		// Cipher对象实际完成解密操作
		Cipher cipher = Cipher.getInstance(DES);
		// 用密匙初始化Cipher对象
		cipher.init(Cipher.DECRYPT_MODE, securekey, sr);
		// 现在，获取数据并解密
		// 正式执行解密操作
		return cipher.doFinal(src);
	}

	/**
	 * 密码解密
	 * 
	 * @param data
	 * @return
	 * @throws Exception
	 */

	public final static String jiemi(String data) {
		try {
			return new String(decrypt(hex2byte(data.getBytes()),
					PASSWORD_CRYPT_KEY.getBytes()));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}
	/**
	 * 密码加密
	 * 
	 * @param password
	 * @return
	 * @throws Exception
	 */

	public final static String jiami(String password) {
		try {
			return byte2hex(encrypt(password.getBytes(), PASSWORD_CRYPT_KEY
					.getBytes()));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

	/**
	 * 二行制转字符串
	 * 
	 * @param b
	 * @return
	 */

	public static String byte2hex(byte[] b) {
		String hs = "";
		String stmp = "";
		for (int n = 0; n < b.length; n++) {
			stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));
			if (stmp.length() == 1)
				hs = hs + "0" + stmp;
			else
				hs = hs + stmp;
		}
		return hs.toUpperCase();
	}

	public static byte[] hex2byte(byte[] b) {
		if ((b.length % 2) != 0)
			throw new IllegalArgumentException("长度不是偶数");
		byte[] b2 = new byte[b.length / 2];
		for (int n = 0; n < b.length; n += 2) {
			String item = new String(b, n, 2);
			b2[n / 2] = (byte) Integer.parseInt(item, 16);
		}
		return b2;
	}
	public static void main(String args[]) {
		String aa = PasswordEnOrDecode.jiami("rr");
		System.out.println("原值："+"098f6bcd4621d373cade4e832627b4f6");
		System.out.println("加密后的密码：" + aa + "==>" + aa.length());
		System.out.println("解密后的密码：" + PasswordEnOrDecode.jiemi(aa));
	}
}

 32位加密

public class Md5 {
	public Md5() {  
	  }  
	  
	  public static String byte2hex(byte[] b) { //二行制转字符串  
	    String hs = "";  
	    String stmp = "";  
	    for (int n = 0; n < b.length; n++) {  
	      stmp = (Integer.toHexString(b[n] & 0XFF));  
	      if (stmp.length() == 1)  
	        hs = hs + "0" + stmp;  
	      else  
	        hs = hs + stmp;  
	      if (n < b.length - 1)  
	        hs = hs;  
	    }  
	    return hs.toUpperCase();  
	  }  
	  
	  public static String getMD5(String password) {  
	    String returnStr = null;  
	    try {  
	      java.security.MessageDigest alga = java.security.MessageDigest.  
	          getInstance("MD5");  
	  
	      alga.update(password.getBytes());  
	      byte[] digesta = alga.digest();  
	      returnStr = byte2hex(digesta);  
	    }  
	    catch (Exception e) {}  
	    return returnStr;  
	  }  
	  
	  public static void main(String args[]) {  
	  
	    Md5 m = new Md5();  
	  
	    System.out.println("MD5 Test suite:");  
	    System.out.println("MD5(\"\"):" + m.getMD5(""));  
	    System.out.println("MD5(\"test\"):" + m.getMD5("test")+"几位数："+m.getMD5("test").length());  
	    System.out.println("MD5(\"abc\"):" + m.getMD5("abc"));  
	    System.out.println("MD5(\"message digest\"):" + m.getMD5("message digest"));  
	    System.out.println("MD5(\"abcdefghijklmnopqrstuvwxyz\"):" +  
	                       m.getMD5("abcdefghijklmnopqrstuvwxyz"));  
	    System.out.println(  
	        "MD5(\"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\"):" +  
	        m.getMD5(  
	        "admin"));  
	  
	  }  
}