Android与Windows平台IntelliJ IDEA间RSA加密解密报错问题求助

大家好，我最近遇到了一个跨平台RSA加密的棘手问题，折腾好几天都没搞定，想请各位大佬帮忙分析下：

我的服务端是Windows上的IntelliJ IDEA项目，客户端是Android应用。原本的逻辑很简单：服务端生成RSA密钥对，把公钥发给客户端，客户端用这个公钥加密消息后回传给服务端，但服务端解密的时候直接抛出了错误。

我做了几个测试来排查问题：

• 如果服务端也换成Android平台，整个加密解密流程完全正常，没有任何问题；
• 把两端角色互换（服务端用Android，客户端用IntelliJ），服务端能成功解密，但解密后的消息后面跟着一堆莫名其妙的乱码符号。

下面是相关的核心代码、工具类以及报错的栈追踪信息：

服务端（IntelliJ）代码 #

ServerSocket serverSocket = new ServerSocket(5556);

Socket socket = serverSocket.accept();

System.out.println("Client connected");

DataOutputStream dOut = new DataOutputStream(socket.getOutputStream());

DataInputStream dIn  = new DataInputStream(socket.getInputStream());

//Create keys
Map<String, Object> RsaKey = rsa.initKey();

String RsaPrivateKey = rsa.getPrivateKey(RsaKey);

String RsaPublicKey = rsa.getPublicKey(RsaKey);

//send key
dOut.writeInt(RsaPublicKey.getBytes().length);
dOut.write(RsaPublicKey.getBytes());

Thread.sleep(1000);

System.out.println(RsaPublicKey);

//read encrypted message
int length_pk = dIn.readInt();
byte[] message = new byte[length_pk];
dIn.readFully(message, 0, message.length);

String st1 = new String(message);
System.out.println(st1 + " " + length_pk + " " + st1.length());

String str = new String(rsa.decryptByPrivateKey(message, RsaPrivateKey));
System.out.println(str);

客户端（Android）代码 #

Socket client = new Socket("192.168.1.103", 5556);

DataOutputStream dOut = new DataOutputStream(client.getOutputStream());
DataInputStream dIn = new DataInputStream(client.getInputStream());

//read key from server
int length_pk1 = dIn.readInt();
byte[] publickeyserver1 = new byte[length_pk1];
dIn.readFully(publickeyserver1, 0, publickeyserver1.length);

String RsaPublicKeyServer = new String(publickeyserver1);

//test key rsa
String str = "Who is there?";
byte[] encbyte = rsa.encryptByPublicKey(str.getBytes(), RsaPublicKeyServer);

dOut.writeInt(encbyte.length);
dOut.write(encbyte);

RSA工具类代码 #

public static final String KEY_ALGORITHM = "RSA";
public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
private static final String PUBLIC_KEY = "RSAPublicKey";
private static final String PRIVATE_KEY = "RSAPrivateKey";

public static byte[] decryptBASE64(String key) throws Exception {
    return Base64.getDecoder().decode(key);
}

public static byte[] decryptByPrivateKey(byte[] data, String key)throws Exception {
    byte[] keyBytes = decryptBASE64(key);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.DECRYPT_MODE, privateKey);
    return cipher.doFinal(data);
}

public static byte[] encryptByPublicKey(byte[] data, String key) throws Exception {
    byte[] keyBytes = decryptBASE64(key);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicKey = keyFactory.generatePublic(x509KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.ENCRYPT_MODE, publicKey);
    return cipher.doFinal(data);
}

public static String getPrivateKey(Map<String, Object> keyMap)throws Exception {
    Key key = (Key) keyMap.get(PRIVATE_KEY);
    return encryptBASE64(key.getEncoded());
}

public static String getPublicKey(Map<String, Object> keyMap)throws Exception {
    Key key = (Key) keyMap.get(PUBLIC_KEY);
    return encryptBASE64(key.getEncoded());
}

public static Map<String, Object> initKey() 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<String, Object> keyMap = new HashMap<String, Object>(2);
    keyMap.put(PUBLIC_KEY, publicKey);
    keyMap.put(PRIVATE_KEY, privateKey);
    return keyMap;
}

报错栈追踪 #

Exception in thread "main" java.lang.RuntimeException:
javax.crypto.BadPaddingException: Decryption error    at
Main.main(Main.java:110) Caused by: javax.crypto.BadPaddingException:
Decryption error  at
java.base/sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:369)
at java.base/sun.security.rsa.RSAPadding.unpad(RSAPadding.java:282)
at
java.base/com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:366)
at
java.base/com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:400)
at java.base/javax.crypto.Cipher.doFinal(Cipher.java:2206)  at
main.java.rsa.decryptByPrivateKey(rsa.java:134)   at
Main.main(Main.java:103)

这个RSA工具类我用了很久，同平台下一直没问题，感觉问题应该出在跨平台的传输编码或者JVM差异上，但就是找不到具体原因，麻烦各位帮忙看看！

备注：内容来源于stack exchange，提问作者Роман Дворниченко