实现：
用RSA非对称加密方式实现。后台生成rsa密钥对，然后在登陆页面设置rsa公钥，提交时用公钥加密密码，生成的密文传到后台，用私钥解密，获取密码明文。
这样客户端只需要知道rsa加密方式和公钥，前台不知道私钥是无法解密的，此解决方案还是相对比较安全的。
附件是参照网友资料的java+JS的实现，放在这里供大家下载。访问方式/RSA/login.jsp。
需要到http://www.bouncycastle.org下载bcprov-jdk14-123.jar文件。
因为后台要转换成bigint，所以对明文长度有些限制：
总长度不超过126（1汉字长度为9），如下两个字符串：
阿送大法散得阿送大法散得阿送
1232132131231231232131232K1232132131231231232131232K1232132131231231232131232K1232132131231231232131232K1234567890123456789012
RSA速度
* 由于进行的都是大数计算，使得RSA最快的情况也比DES慢上100倍，无论 是软件还是硬件实现。
* 速度一直是RSA的缺陷。一般来说只用于少量数据 加密。
Util.java
package RSA;
/**
*
*/
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import javax.crypto.Cipher;
/**
* RSA 工具类。提供加密，解密，生成密钥对等方法。
* 需要到http://www.bouncycastle.org下载bcprov-jdk14-123.jar。
*
*/
public class RSAUtil {
private static String RSAKeyStore = "C:/RSAKey.txt";
/**
* * 生成密钥对 *
*
* @return KeyPair *
* @throws EncryptException
*/
public static KeyPair generateKeyPair() throws Exception {
try {
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",
new org.bouncycastle.jce.provider.BouncyCastleProvider());
final int KEY_SIZE = 1024;// 没什么好说的了，这个值关系到块加密的大小，可以更改，但是不要太大，否则效率会低
keyPairGen.initialize(KEY_SIZE, new SecureRandom());
KeyPair keyPair = keyPairGen.generateKeyPair();
System.out.println(keyPair.getPrivate());
System.out.println(keyPair.getPublic());
saveKeyPair(keyPair);
return keyPair;
} catch (Exception e) {
throw new Exception(e.getMessage());
}
}
public static KeyPair getKeyPair() throws Exception {
FileInputStream fis = new FileInputStream(RSAKeyStore);
ObjectInputStream oos = new ObjectInputStream(fis);
KeyPair kp = (KeyPair) oos.readObject();
oos.close();
fis.close();
return kp;
}
public static void saveKeyPair(KeyPair kp) throws Exception {
FileOutputStream fos = new FileOutputStream(RSAKeyStore);
ObjectOutputStream oos = new ObjectOutputStream(fos);
// 生成密钥
oos.writeObject(kp);
oos.close();
fos.close();
}
/**
* * 生成公钥 *
*
* @param modulus *
* @param publicExponent *
* @return RSAPublicKey *
* @throws Exception
*/
public static RSAPublicKey generateRSAPublicKey(byte[] modulus,
byte[] publicExponent) throws Exception {
KeyFactory keyFac = null;
try {
keyFac = KeyFactory.getInstance("RSA",
new org.bouncycastle.jce.provider.BouncyCastleProvider());
} catch (NoSuchAlgorithmException ex) {
throw new Exception(ex.getMessage());
}
RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(
modulus), new BigInteger(publicExponent));
try {
return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
} catch (InvalidKeySpecException ex) {
throw new Exception(ex.getMessage());
}
}
/**
* * 生成私钥 *
*
* @param modulus *
* @param privateExponent *
* @return RSAPrivateKey *
* @throws Exception
*/
public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus,
byte[] privateExponent) throws Exception {
KeyFactory keyFac = null;
try {
keyFac = KeyFactory.getInstance("RSA",
new org.bouncycastle.jce.provider.BouncyCastleProvider());
} catch (NoSuchAlgorithmException ex) {
throw new Exception(ex.getMessage());
}
RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(
modulus), new BigInteger(privateExponent));
try {
return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
} catch (InvalidKeySpecException ex) {
throw new Exception(ex.getMessage());
}
}
/**
* * 加密 *
*
* @param key
* 加密的密钥 *
* @param data
* 待加密的明文数据 *
* @return 加密后的数据 *
* @throws Exception
*/
public static byte[] encrypt(PublicKey pk, byte[] data) throws Exception {
try {
Cipher cipher = Cipher.getInstance("RSA",
new org.bouncycastle.jce.provider.BouncyCastleProvider());
cipher.init(Cipher.ENCRYPT_MODE, pk);
int blockSize = cipher.getBlockSize();// 获得加密块大小，如：加密前数据为128个byte，而key_size=1024
// 加密块大小为127
// byte,加密后为128个byte;因此共有2个加密块，第一个127
// byte第二个为1个byte
int outputSize = cipher.getOutputSize(data.length);// 获得加密块加密后块大小
int leavedSize = data.length % blockSize;
int blocksSize = leavedSize != 0 ? data.length / blockSize + 1
: data.length / blockSize;
byte[] raw = new byte[outputSize * blocksSize];
int i = 0;
while (data.length - i * blockSize > 0) {
if (data.length - i * blockSize > blockSize)
cipher.doFinal(data, i * blockSize, blockSize, raw, i
* outputSize);
else
cipher.doFinal(data, i * blockSize, data.length - i
* blockSize, raw, i * outputSize);
// 这里面doUpdate方法不可用，查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到
// ByteArrayOutputStream中，而最后doFinal的时候才将所有的byte[]进行加密，可是到了此时加密块大小很可能已经超出了
// OutputSize所以只好用dofinal方法。
i++;
}
return raw;
} catch (Exception e) {
throw new Exception(e.getMessage());
}
}
/**
* * 解密 *
*
* @param key
* 解密的密钥 *
* @param raw
* 已经加密的数据 *
* @return 解密后的明文 *
* @throws Exception
*/
public static byte[] decrypt(PrivateKey pk, byte[] raw) throws Exception {
try {
Cipher cipher = Cipher.getInstance("RSA",
new org.bouncycastle.jce.provider.BouncyCastleProvider());
cipher.init(cipher.DECRYPT_MODE, pk);
int blockSize = cipher.getBlockSize();
ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
int j = 0;
while (raw.length - j * blockSize > 0) {
bout.write(cipher.doFinal(raw, j * blockSize, blockSize));
j++;
}
return bout.toByteArray();
} catch (Exception e) {
throw new Exception(e.getMessage());
}
}
/**
* * *
*
* @param args *
* @throws Exception
*/
public static void main(String[] args) throws Exception {
RSAPublicKey rsap = (RSAPublicKey) RSAUtil.generateKeyPair().getPublic();
String test = "hello world";
byte[] en_test = encrypt(getKeyPair().getPublic(), test.getBytes());
byte[] de_test = decrypt(getKeyPair().getPrivate(), en_test);
System.out.println(new String(de_test));
}
}
LoginAction.java
package RSA;
//login
/*
* Generated by MyEclipse Struts
* Template path: templates/java/JavaClass.vtl
*/
import java.math.BigInteger;
import java.net.URLDecoder;
import java.net.URLEncoder;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import RSA.RSAUtil;
/**
* MyEclipse Struts Creation date: 06-28-2008
*
* XDoclet definition:
*
* @struts.action path="/login" name="loginForm" input="/login.jsp"
* scope="request" validate="true"
* @struts.action-forward name="error" path="/error.jsp"
* @struts.action-forward name="success" path="/success.jsp"
*/
public class LoginAction {
/*
* Generated Methods
*/
/**
* Method execute
*
* @param mapping
* @param form
* @param request
* @param response
* @return ActionForward
*/
public boolean execute(HttpServletRequest request,
HttpServletResponse response) throws Exception {
String pwd ;
String result = request.getParameter("result");
System.out.println("原文加密后为：");
System.out.println(result);
byte[] en_result = new BigInteger(result, 16).toByteArray();
//System.out.println("转成byte[]" + new String(en_result));
byte[] de_result = RSAUtil.decrypt(RSAUtil.getKeyPair().getPrivate(),
en_result);
System.out.println("还原密文：");
System.out.println(new String(de_result));
StringBuffer sb = new StringBuffer();
sb.append(new String(de_result));
pwd = sb.reverse().toString();
System.out.println(sb);
System.out.println("=================================");
pwd = URLDecoder.decode(pwd,"UTF-8");//
System.out.println(pwd);
request.setAttribute("pwd", pwd);
return true;
}
}
登陆login.jsp
<%@ page language="java" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>login</title>
<script type="text/javascript" src="js/RSA.js"></script>
<script type="text/javascript" src="js/BigInt.js"></script>
<script type="text/javascript" src="js/Barrett.js"></script>
<script type="text/javascript">
function rsalogin(){
var thisPwd = document.getElementById("password").value;
bodyRSA();
var result = encryptedString(key, encodeURIComponent(thisPwd));
//alert(encodeURIComponent(thisPwd)+"\r\n"+result);
loginForm.action="loginCHK.jsp?result="+result;
loginForm.submit();
}
var key ;
function bodyRSA(){
setMaxDigits(130);
key = new RSAKeyPair("10001","","8246a46f44fc4d961e139fd70f4787d272d374532f4d2d9b7cbaad6a15a8c1301319aa6b3f30413b859351c71938aec516fa7147b69168b195e81df46b6bed7950cf3a1c719d42175f73d7c97a85d7d20a9e83688b92f05b3059bb2ff75cd7190a042cd2db97ebc2ab4da366f2a7085556ed613b5a39c9fdd2bb2595d1dc23b5");
}
</script>
</head>
<body>
<form method="post" name="loginForm" target=_blank>
<table border="0">
<tr>
<td>
Password:
</td>
<td>
<input type='text' name="password" id=password style='width:400px' value="my passwd"/>
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="button" value="SUBMIT" onclick="rsalogin();" />
</td>
</tr>
</table>
</form>
</body>
</html:html>
登陆校验loginCHK.jsp
<%@ page language="java" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<jsp:directive.page import="RSA.LoginAction"/>
<%
LoginAction la = new LoginAction();
la.execute(request ,response);
%>
pwd is [<%=request.getAttribute("pwd")%>]
另外，通过RSA还可以实现数字签名 ：用私钥签名、公钥验证即可。具体可以看代码：
package encode;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Signature;
public class DigitalSignature2Example {
public static void main(String[] args) {
args = new String[] { "中国" };
if (args.length != 1) {
System.err.println("Usage:java DigitalSignature2Example ");
System.exit(1);
}
try {
byte[] plainText = args[0].getBytes("UTF-8");
System.out.println("\nStart generating RSA key.");
// 生成RSA密钥对
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
// 初始化密钥长度
keyGen.initialize(1024);
// 生成密钥对
KeyPair pair = keyGen.generateKeyPair();
System.out.println("\nFinish generating RSA key.");
// 使用私钥签名
Signature sig = Signature.getInstance("SHA1WithRSA");
// 用指定的私钥进行初始化
sig.initSign(pair.getPrivate());
// 添加要签名的信息
sig.update(plainText);
// 返回签名的字节数组
byte[] signature = sig.sign();
System.out.println(sig.getProvider().getInfo());
System.out.println("\nSignature: ");
System.out.println(new String(signature, "UTF-8"));
// 使用公钥验证
System.out.println("\nStart signature verification.");
sig.initVerify(pair.getPublic());
// 添加要验证的信息
sig.update(plainText);
if (sig.verify(signature)) {
System.out.println("Signature verificated.");
} else {
System.out.println("Signature failed.");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}