#Android笔记#通过RSA加密请求参数，防止数据被抓包
最近在做南京某高校的电子班牌项目，其中涉及到一些敏感数据，需要做一定的加密处理。正好之前实习的时候，做过一个课程电子书的项目，也是高校相关的，领导希望将其中的课程讲义进行加密处理，防止app被反编译或抓包后泄漏信息，那段时间研究对比了不少加密算法，比如AES、DES、MD5和RSA等（有说说为证～
），综合考虑下来，RSA是目前比较靠谱的选择，当时就使用了RSA加密算法，只可惜当时没有记录，现在想用的时候，又得去查阅资料，这次就把它记录下来吧！
RSA加密算法，是一种“由已知加密密钥推导出解密密钥在计算上是不可行的”密码体制。在公开密钥密码体制中，加密密钥（即公开密钥）PK是公开信息，而解密密钥（即秘密密钥）SK是需要保密的。加密算法E和解密算法D也都是公开的。虽然解密密钥SK是由公开密钥PK决定的，由于无法计算出大数n的欧拉函数phi(N)，所以不能根据PK计算出SK。
通过RSA加密请求参数的大致思路就是：客户端通过公钥将请求参数进行加密，服务端拿到加密字符串后通过私钥对请求参数进行解密，并进行对应的业务处理。在实际操作中发现，直接通过RSA加密的字符串是一串类似乱码的字符串，在本地是可以解密的，但是传到服务端后就无法解密了，因此使用了BASE64对数据串进行了编码，服务端再进行一次解码，即可继续进行解密。
下面是一个在Android中实现的例子：
MainActivity.java:
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.yuyan.rsatest.utils.Base64;
import com.yuyan.rsatest.utils.RSAUtils;
import static com.yuyan.rsatest.utils.Constant.DEFAULT_PRIVATE_KEY;
import static com.yuyan.rsatest.utils.Constant.DEFAULT_PUBLIC_KEY;
public class MainActivity extends AppCompatActivity {
private EditText ed_input;
private TextView tv_encrypt,tv_decrypt;
private Button btn_start;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ed_input = findViewById(R.id.ed_input);
tv_encrypt = findViewById(R.id.tv_encrypt);
tv_decrypt = findViewById(R.id.tv_decrypt);
btn_start = findViewById(R.id.btn_start);
btn_start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String input = ed_input.getText().toString();
try {
if (!TextUtils.isEmpty(input)) {
byte[] data = input.getBytes();
//模拟客户端数据通过公钥加密
byte[] encryptedByte = RSAUtils.encryptByPublicKey(data, DEFAULT_PUBLIC_KEY);
//通过base64编码
String encrypted = Base64.encode(encryptedByte);
tv_encrypt.setText("加密后的文字：" + encrypted);
//解码base64串
byte[] decrypted = Base64.decode(encrypted);
//模拟服务端数据通过私钥进行解码
byte[] decodedData = RSAUtils.decryptByPrivateKey(decrypted,
DEFAULT_PRIVATE_KEY);
String target = new String(decodedData);
tv_decrypt.setText("解密后的文字：" + target);
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}RSAUtils.java:import java.io.ByteArrayOutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
import javax.crypto.Cipher;
public class RSAUtils {
/** *//**
* 加密算法RSA
*/
public static final String KEY_ALGORITHM = "RSA";
/** *//**
* 签名算法
*/
public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
/** *//**
* 获取公钥的key
*/
private static final String PUBLIC_KEY = "RSAPublicKey";
/** *//**
* 获取私钥的key
*/
private static final String PRIVATE_KEY = "RSAPrivateKey";
/** *//**
* RSA最大加密明文大小
*/
private static final int MAX_ENCRYPT_BLOCK = 117;
/** *//**
* RSA最大解密密文大小
*/
private static final int MAX_DECRYPT_BLOCK = 128;
/** *//**
*
* 生成密钥对(公钥和私钥)
*
*
* @return
* @throws Exception
*/
public static Map genKeyPair() throws Exception {
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
keyPairGen.initialize(1024);
KeyPair keyPair = keyPairGen.generateKeyPair();
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
Map keyMap = new HashMap(2);
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
/** *//**
*
* 用私钥对信息生成数字签名
*
*
* @param data 已加密数据
* @param privateKey 私钥(BASE64编码)
*
* @return
* @throws Exception
*/
public static String sign(byte[] data, String privateKey) throws Exception {
byte[] keyBytes = Base64Utils.decode(privateKey);
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initSign(privateK);
signature.update(data);
return Base64Utils.encode(signature.sign());
}
/** *//**
*
* 校验数字签名
*
*
* @param data 已加密数据
* @param publicKey 公钥(BASE64编码)
* @param sign 数字签名
*
* @return
* @throws Exception
*
*/
public static boolean verify(byte[] data, String publicKey, String sign)
throws Exception {
byte[] keyBytes = Base64Utils.decode(publicKey);
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
PublicKey publicK = keyFactory.generatePublic(keySpec);
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initVerify(publicK);
signature.update(data);
return signature.verify(Base64Utils.decode(sign));
}
/** *//**
*
* 私钥解密
*
*
* @param encryptedData 已加密数据
* @param privateKey 私钥(BASE64编码)
* @return
* @throws Exception
*/
public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
throws Exception {
byte[] keyBytes = Base64Utils.decode(privateKey);
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM,"BC");
Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
// Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
Cipher cipher = Cipher.getInstance("RSA/None/PKCS1Padding");
cipher.init(Cipher.DECRYPT_MODE, privateK);
int inputLen = encryptedData.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分段解密
while (inputLen - offSet > 0) {
if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
} else {
cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
}
out.write(cache, 0, cache.length);
i++;
offSet = i * MAX_DECRYPT_BLOCK;
}
byte[] decryptedData = out.toByteArray();
out.close();
return decryptedData;
}
/** *//**
*
* 公钥解密
*
*
* @param encryptedData 已加密数据
* @param publicKey 公钥(BASE64编码)
* @return
* @throws Exception
*/
public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
throws Exception {
byte[] keyBytes = Base64Utils.decode(publicKey);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicK = keyFactory.generatePublic(x509KeySpec);
// Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
Cipher cipher = Cipher.getInstance("RSA/None/PKCS1Padding");
cipher.init(Cipher.DECRYPT_MODE, publicK);
int inputLen = encryptedData.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分段解密
while (inputLen - offSet > 0) {
if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
} else {
cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
}
out.write(cache, 0, cache.length);
i++;
offSet = i * MAX_DECRYPT_BLOCK;
}
byte[] decryptedData = out.toByteArray();
out.close();
return decryptedData;
}
/** *//**
*
* 公钥加密
*
*
* @param data 源数据
* @param publicKey 公钥(BASE64编码)
* @return
* @throws Exception
*/
public static byte[] encryptByPublicKey(byte[] data, String publicKey)
throws Exception {
byte[] keyBytes = Base64Utils.decode(publicKey);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicK = keyFactory.generatePublic(x509KeySpec);
// 对数据加密
// Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
Cipher cipher = Cipher.getInstance("RSA/None/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, publicK);
int inputLen = data.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分段加密
while (inputLen - offSet > 0) {
if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
} else {
cache = cipher.doFinal(data, offSet, inputLen - offSet);
}
out.write(cache, 0, cache.length);
i++;
offSet = i * MAX_ENCRYPT_BLOCK;
}
byte[] encryptedData = out.toByteArray();
out.close();
return encryptedData;
}
/** *//**
*
* 私钥加密
*
*
* @param data 源数据
* @param privateKey 私钥(BASE64编码)
* @return
* @throws Exception
*/
public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
throws Exception {
byte[] keyBytes = Base64Utils.decode(privateKey);
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
// Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
Cipher cipher = Cipher.getInstance("RSA/None/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, privateK);
int inputLen = data.length;
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] cache;
int i = 0;
// 对数据分段加密
while (inputLen - offSet > 0) {
if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
} else {
cache = cipher.doFinal(data, offSet, inputLen - offSet);
}
out.write(cache, 0, cache.length);
i++;
offSet = i * MAX_ENCRYPT_BLOCK;
}
byte[] encryptedData = out.toByteArray();
out.close();
return encryptedData;
}
/** *//**
*
* 获取私钥
*
*
* @param keyMap 密钥对
* @return
* @throws Exception
*/
public static String getPrivateKey(Map keyMap)
throws Exception {
Key key = (Key) keyMap.get(PRIVATE_KEY);
return Base64Utils.encode(key.getEncoded());
}
/** *//**
*
* 获取公钥
*
*
* @param keyMap 密钥对
* @return
* @throws Exception
*/
public static String getPublicKey(Map keyMap)
throws Exception {
Key key = (Key) keyMap.get(PUBLIC_KEY);
return Base64Utils.encode(key.getEncoded());
} 核心的加密解密代码就是以上这些了，如果想查看整个demo的话，可点击这里下载。
通过这种方式，请求的参数就被加密成了密文了，这样即使别人抓到了你的请求，也不知道该如何去动态抓包你的数据；当然了，他可以直接拿着你的加密串去拿固定的结果，所以最好在数据串中加入时间戳等验证字段或者数字签名等，服务端在验证后再返回结果，虽说在一定程度上牺牲了速度，但是却最大程度的保证了安全。以上。