MD5加密

import java.security.Key;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;

public class Util {
	/**
	 * 加密方法
	 * @param data：要加密的数据
	 * @param key：秘钥
	 * @return
	 * @throws Exception
	 */
	public static String encryption(String data,String key) throws Exception{
		try
        {
            DESKeySpec dks = new DESKeySpec(key.getBytes());
             
            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
            //key的长度不能够小于8位字节
            Key secretKey = keyFactory.generateSecret(dks);
            Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
            IvParameterSpec iv = new IvParameterSpec("12345678".getBytes());
            AlgorithmParameterSpec paramSpec = iv;
            cipher.init(Cipher.ENCRYPT_MODE, secretKey,paramSpec);
            byte[] bytes = cipher.doFinal(data.getBytes());
            String str=byte2HexString(bytes); 
            return str;
        } catch (Exception e)
        {
            throw new Exception(e);
        }
	}
	
	/**
     * byte[]转换成字符串
     * @param b
     * @return
     */
	static String byte2HexString(byte[] b)
    {
	     StringBuffer sb = new StringBuffer();
	     int length = b.length;
	     for (int i = 0; i < length; i++) {
	    	 String stmp = Integer.toHexString(b[i]&0xff);
	    	 if(stmp.length() == 1)
	    		 sb.append("0"+stmp);
	    	 else
	    		 sb.append(stmp);
	     }
	     return sb.toString();
    }
	
	/**
	 * 解密方法
	 * @param data：要解密的数据
	 * @param key：秘钥
	 * @return
	 * @throws Exception
	 */
	public static String decryption(String data,String key) throws Exception{
		try
        {
            DESKeySpec dks = new DESKeySpec(key.getBytes());
            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
            //key的长度不能够小于8位字节
            Key secretKey = keyFactory.generateSecret(dks);
            Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
            IvParameterSpec iv = new IvParameterSpec("12345678".getBytes());
            AlgorithmParameterSpec paramSpec = iv;
            cipher.init(Cipher.DECRYPT_MODE, secretKey,paramSpec);
            String str=new String(cipher.doFinal(String2Byte(data))); 
            return str;
        } catch (Exception e)
        {
            throw new Exception(e);
        }
	}
	
	/**
     * 16进制转换成byte[]
     * @param hexString
     * @return
     */
	static byte[] String2Byte(String hexString)
    {
	     if(hexString.length() % 2 ==1)
	    	 return null;
	     byte[] ret = new byte[hexString.length()/2];
	     for (int i = 0; i < hexString.length(); i+=2) {
	    	 ret[i/2] = Integer.decode("0x"+hexString.substring(i,i+2)).byteValue();
	     }
	     return ret;
    }
}

 

加密实例：

try {
			String string="广州市";
			String encryption = null;
			encryption=Util.encryption(string, "abcdefghijk");
			Log.i("加密后的字符串：",encryption);
			String decryption=null;
			decryption=Util.decryption(encryption, "abcdefghijk");
			Log.i("解密后的字符串：", decryption);
		} catch (Exception e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		}

 运行结果：

 02-06 15:56:09.840: I/加密后的字符串：(20768): f9618e92794af394
02-06 15:56:09.850: I/解密后的字符串：(20768): 广州