Java RSA BadPaddingException

Question

我正在尝试与客户端和服务器执行 Diffie-Hellman 密钥交换，但由于某种原因，当我去解密发送到服务器的消息时。我收到以下异常：

Unable to decrypt ciphertext. -> Decryption error
javax.crypto.BadPaddingException: Decryption error
    at java.base/sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:378)
    at java.base/sun.security.rsa.RSAPadding.unpad(RSAPadding.java:290)
    at java.base/com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:359)
    at java.base/com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:392)
    at java.base/javax.crypto.Cipher.doFinal(Cipher.java:2205)
    at server.Server.decrypt(Server.java:354)
    at server.Server.performDHKEX(Server.java:242)
    at server.Server.<init>(Server.java:145)
    at server.Driver.main(Driver.java:15)

我知道我的 Encryption/Decryption 方法工作得很好，因为如果我这样做：decrypt(encrypt(bytes))，不会抛出异常。有谁知道为什么会这样？下面是我的客户端和服务器代码。

TIA！

客户

private SecretKey performDHKEX()
    {   
        SecretKey sharedKey = null;
        
        try
        {
            // Send a message telling the server to get ready for a DH-KEX.
            outputStream.writeObject("DO_DH_KEX");
            
            KeyAgreement ecdhKex = KeyAgreement.getInstance("ECDH");
            KeyPairGenerator gen = KeyPairGenerator.getInstance("EC");
            KeyPair keyPair = gen.genKeyPair();
            
            // Send the Client's Public Value.
            byte[] cText = encrypt(keyPair.getPublic().getEncoded());
            decrypt(encrypt(keyPair.getPublic().getEncoded()));
            byte[] sign = sign(keyPair.getPublic().getEncoded());
            outputStream.writeObject(cText);
            outputStream.writeObject(X509_CERTIFICATE);
            
            
            // Start the exchange with Private Key.
            ecdhKex.init(keyPair.getPrivate());
            
            /* Wait for the response from the Server, then decrypt and load the
            public value the Server sent. */
            byte[][] recvCipherText = (byte[][]) inputStream.readObject();  
            X509Certificate serverCert = (X509Certificate) inputStream
                    .readObject();
            byte[] plainText = decrypt(recvCipherText[0]);
            
            // If the signature verifies, build a keyspec from the public value.
            if (verify(recvCipherText[1], plainText, serverCert))
            {
                // Create a new PublicKey from the Server's Public Value.
                PublicKey pub = KeyFactory.getInstance("EC")
                        .generatePublic(new X509EncodedKeySpec(plainText));
               
                // Perform the last step of the KEX and create a new SecretKey.
                ecdhKex.doPhase(pub, true);
                
                // Use the first 16 bytes of the generate secret for a key.
                sharedKey = new SecretKeySpec(Arrays.copyOfRange(ecdhKex
                        .generateSecret(), 0, 16), "AES");
            }
            else
                System.err.println("Error verifying signature.");
            
        } catch (IOException | ClassNotFoundException | IllegalStateException | 
                InvalidKeyException | NoSuchAlgorithmException | 
                InvalidKeySpecException ex)
        {
            System.err.println("Error during DH-KEX -> " + ex.getMessage());
        }
        
        System.out.println(Base64.getEncoder().encodeToString(sharedKey.getEncoded()));
        return sharedKey;
    }

服务器

private SecretKey performDHKEX()
    {      
        SecretKey sharedKey = null;
        
        try
        {
            KeyAgreement ecdhKex = KeyAgreement.getInstance("ECDH");
            KeyPairGenerator gen = KeyPairGenerator.getInstance("EC");
            KeyPair keyPair = gen.genKeyPair();
            
            byte[] recvMessage = (byte[]) inputStream.readObject();
            X509Certificate clientCert = (X509Certificate) inputStream
                    .readObject();
            
            // Decrypt the ciphertext.
            byte[] plainText = decrypt(recvMessage); // EXCEPTION THROWN HERE
             
            // If the signature and certificate verify, complete the KEX.
            if (verify(recvMessage, plainText, clientCert))
            {
                System.out.println("inside verify");
                // Send the Server's Public Value.
                byte[] sign = sign(keyPair.getPublic().getEncoded());
                byte[] cText = encrypt(keyPair.getPublic().getEncoded());  
                byte[][] sendArray = {cText, sign};
                outputStream.writeObject(sendArray);
                outputStream.writeObject(X509_CERTIFICATE);
                
                PublicKey pub = KeyFactory.getInstance("EC")
                        .generatePublic(new X509EncodedKeySpec(plainText));
                
                // Start the exchange with the server's Private Value and then
                // doPhase with the Client's public Value.
                ecdhKex.init(keyPair.getPrivate());
                ecdhKex.doPhase(pub, true);
                
                // Use the first 16 bytes of the generate secret for a key.
                sharedKey = new SecretKeySpec(Arrays.copyOfRange(ecdhKex
                        .generateSecret(), 0, 16), "AES");
            }
            
        } catch (IOException | ClassNotFoundException | IllegalStateException | 
                InvalidKeyException | NoSuchAlgorithmException | 
                InvalidKeySpecException ex)
        {
            System.err.println("Error during DH-KEX -> " + ex.getMessage());
        }
        
        System.out.println(Base64.getEncoder().encodeToString(sharedKey.getEncoded()));
        
        return sharedKey;
    }

加密

 private byte[] encrypt(byte[] message)
    {
        byte[] cipherText = null;
        
        try
        {
            rsaCipher.init(Cipher.ENCRYPT_MODE, PRIV_KEY);
            cipherText = rsaCipher.doFinal(message);
        } catch (InvalidKeyException | BadPaddingException | 
                IllegalBlockSizeException ex)
        {
            System.err.println("Error encrypting message. -> " + ex
                    .getMessage());
            ex.printStackTrace();
        }
        
        return cipherText;
    }

解密

private byte[] decrypt(byte[] cipherText)
    {
        try
        {
            rsaCipher.init(Cipher.DECRYPT_MODE, PUB_KEY);
            return rsaCipher.doFinal(cipherText);
        } catch (InvalidKeyException | IllegalBlockSizeException | 
                BadPaddingException ex)
        {
            System.err.println("Unable to decrypt ciphertext. -> " + ex
                    .getMessage());
            ex.printStackTrace();
        }
        
        return null;
    }

为了澄清，RSA 密码是 RSA/ECB/PKCS1Padding，PRIV_KEY/PUB_KEY 是从 KeyTool

生成的

Answer 1

当使用错误的密钥执行解密时，BadPaddingExceptions 是一种非常常见的故障模式。

服务器必须使用客户端的 public 密钥进行解码，同时使用自己的密钥进行编码。

同样，客户端必须使用服务器的 public 密钥解码并使用自己的密钥进行编码。

您执行的测试表明解码和编码使用的是本地 public 密钥，而不是发件人的 public 密钥。

Java RSA BadPaddingException

Java RSA BadPaddingException

java

encryption

cryptography

rsa