用JAVA设计一个简单的加密、解密算法，用该算法来实现对数据的加密、解密

给你个MD5的加密算法

package test;
import java.security.MessageDigest;
/**
*

Title:

*

Description:

*

Copyright: Copyright (c) 2003

*

Company:

* @author unascribed
* @version 1.0
*/

public class StringUtil {

private final static String[] hexDigits = {
"0", "1", "2", "3", "4", "5", "6", "7",
"8", "9", "a", "b", "c", "d", "e", "f"};

/**
* 转换字节数组为16进制字串
* @param b 字节数组
* @return 16进制字串
*/

public static String byteArrayToHexString(byte[] b) {
StringBuffer resultSb = new StringBuffer();
for (int i = 0; i < b.length; i++) {
resultSb.append(byteToHexString(b[i]));
}
return resultSb.toString();
}

private static String byteToHexString(byte b) {
int n = b;
if (n < 0)
n = 256 + n;
int d1 = n / 16;
int d2 = n % 16;
return hexDigits[d1] + hexDigits[d2];
}

public static String MD5Encode(String origin) {
String resultString = null;

try {
resultString=new String(origin);
MessageDigest md = MessageDigest.getInstance("MD5");
resultString=byteArrayToHexString(md.digest(resultString.getBytes()));
}
catch (Exception ex) {

}
return resultString;
}

public static void main(String[] args){
System.err.println(MD5Encode("a"));
}
}

在RFC 1321中，给出了Test suite用来检验你的实现是否正确：

MD5 ("") = d41d8cd98f00b204e9800998ecf8427e
MD5 ("a") = 0cc175b9c0f1b6a831c399e269772661
MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72
MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0
MD5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13b

还MD5算法，大哥，你别拿出来了，你那个轻松就解密了，可逆性太强了
MD5是根据矩形阵列算法，然后根据64位字符加密的，不可逆的

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5
{
public static String calcMD5(String str)
{
try
{
MessageDigest alga = MessageDigest.getInstance("SHA-1");
alga.update(str.getBytes());
byte[] digesta = alga.digest();
return byte2hex(digesta);
}
catch (NoSuchAlgorithmException ex)
{
System.out.println("wrong");
}
return "NULL";
}

public static String byte2hex(byte[] b)
{
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;
}

public static boolean checkEncryption(String source,String result)
{
boolean flag=false;
if(result.equals(calcMD5(source)))
{
flag=true;
}
return flag;
}
}
MD5加密类，我之前写的！