java - RSA 加密中的 BadPaddingException

Question

我的 RSA 加密程序中出现 BadPaddingException。我不知道为什么会发生。

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;


public class Crypter
{


    private static final String text="Hallo";


    public static byte[] encryptObject(Nachricht msg,PublicKey pubkey) //verschlüsselt das Objekt im CipherStream
    {
        Cipher cipher;
        try
        {
            cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, pubkey);

            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            CipherOutputStream cos = new CipherOutputStream(bos, cipher); 
            ObjectOutputStream oos = new ObjectOutputStream(cos); 
            oos.writeObject(msg); 
            oos.flush();

            byte[] encryptedBytes = bos.toByteArray();  
            return encryptedBytes;

            //weiss nicht was ich zurückgeben soll 
            //den ObjectOutputStream
            //oder die verschlüsselten Bytes


            //byte[] encryptedBytes = bos.toByteArray();  

        } catch (NoSuchAlgorithmException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidKeyException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;

    }

    public static Nachricht decryptObject(PrivateKey privKey,byte[] encryptedBytes) //entschlüsselt das Object
    {
        Nachricht  msg=null;
        try
        {
            Cipher cipher = Cipher.getInstance("RSA");

            cipher.init(Cipher.DECRYPT_MODE, privKey);
            ByteArrayInputStream bin = new ByteArrayInputStream(encryptedBytes);
            CipherInputStream cin = new CipherInputStream(bin, cipher);
            ObjectInputStream in = new ObjectInputStream(cin);
            return (Nachricht) in.readObject();


        } catch (InvalidKeyException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }



        return null;
    }




    //verschlüsselt Text
    public static byte[] encryptBytes(PublicKey key, byte[] plain)
    {
        byte[] chiffre=null;

        try
        {
            Cipher cipher=Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, key);

            chiffre= cipher.doFinal(plain);

            return chiffre; //verschlüsseltes byte[]

        } catch (NoSuchAlgorithmException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidKeyException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalBlockSizeException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (BadPaddingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null; 

    }
    //entschlüsselt Text
    public static byte[] decryptBytes(PrivateKey key, byte[] chiffre)
    {

        try
        {
            Cipher cipher=Cipher.getInstance("RSA");
            cipher.init(cipher.DECRYPT_MODE,key);

            byte[] btext= cipher.doFinal(chiffre);
            return btext;


        } catch (NoSuchAlgorithmException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidKeyException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalBlockSizeException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (BadPaddingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null; //er meckert sonst....
    }



    public static void main(String [] args)
    {


        try
        {


            //KeyPair und Keys managen
            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
            keyPairGen.initialize(1024);
            KeyPair keypair=keyPairGen.generateKeyPair();
            PrivateKey privKey=keypair.getPrivate();
            PublicKey pubKey=keypair.getPublic();

            //Text->Byte
            //Byte->Text
            System.out.println("\n\nTest");
            String testtext= "h";
            byte[] testbyte=testtext.getBytes();
            System.out.println(testbyte);
            testtext=new String(testbyte);
            System.out.println(testtext);
            System.out.println("\n\n");

            //Text->Byte[] text
            //byte[] text->encrypt
            //byte[]encrypt-> decrypt
            //byte[] decrypt->String
            System.out.println("Ausgangstext:");
            System.out.println(text);
            System.out.println("1)Text als byte[] unverschlüsselt");
            byte[] bytetext=text.getBytes(); //in byte[] umgewandelt
            System.out.println( bytetext); //bytetext anzeigen lassen
            System.out.println("2) byte[] verschlüsselt");
            byte[] encrypt=encryptBytes(pubKey,bytetext); //verschlüsseln des byte[]
            System.out.println( encrypt); //ausgeben lassen
            System.out.println("3) byte[] entschlüsselt");
            byte[]decrypt=decryptBytes(privKey,encrypt); //entschlüsseln lassen
            String text=new String(decrypt);
            System.out.println(text);
            //String s = new String(bytes);

            //Object->byte[]
            //byte[] object-> byte[] encrypt
            //byte[] encrypt -> byte[]decrypt
            //byte[] decrypt -> object
            System.out.println("Ausgangsobjekt:");
            Nachricht  msg=new Nachricht();
            msg.setNachricht("Hallo");
            //verschlüsseln des Objekts
            byte[] vObject=encryptObject(msg,pubKey);
            System.out.println("Test ");
            Nachricht neuemsg=decryptObject(privKey,vObject);
            System.out.println("Test2");
            String nachricht=neuemsg.getNachricht();
            System.out.println(nachricht);










        } catch (NoSuchAlgorithmException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }






    }

}

非常感谢您的帮助或提示!我编写的处理字符串加密的函数工作正常，如主函数中所示。我不知道该添加什么。该代码通过了“测试”系统输出，但也引发了一些异常。我希望您知道缺少什么或我必须添加什么才能使其正常工作。

Answer 1

问题的直接原因是您忘记在 ObjectOutputStream 上调用此方法(它会关闭包括 CipherOutputStream 在内的所有其他流):

oos.close();

来自 CipherOutputStream.close 的 JavaDocs :

This method invokes the doFinal method of the encapsulated cipher object, which causes any bytes buffered by the encapsulated cipher to be processed.

因此，对于某些密码，刷新可能会导致某些字节加密，但不会在末尾添加填充。

但是还有很多其他事情也会引起悲伤:

1. 您没有指定应使用哪个填充，因此这在其他 Java 安装上可能会有所不同，请参阅一些建议:JavaDoc for Cipher或者例如this question
2. 如果您的对象变大一点(或者您使用不同的填充来占用更多空间)，则加密的结果是一个 0 字节的数组，不会引发任何异常。另请参阅:this question这建议使用 AES 等对称密码进行加密，并且仅使用 RSA 加密 AES key 。 (或者将 key 大小加倍，并在每次 key 大小加倍时准备好 7 或 8 倍的 CPU 时间，请参阅: this question for a little more info )
3. 您应该知道 String.toBytes() 和 String(byte[]) 都使用默认编码，在其他计算机上可能有所不同，请确保指定例如 java.nio.charset.StandardCharSets.UTF_8

免费建议:如果您要将“Nachricht”(消息)交换到另一台计算机，并且想要真正安全、快速、简单(在某种程度上)和万无一失的东西，我建议您使用 TLS(或 DTLS)，它基于 25 年的研究和实践。