RSA加密中出现BadPaddingException

Question

我在RSA加密程序中遇到BadPaddingException。我不知道为什么会发生这种事。

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("nnTest");
String testtext= "h";
byte[] testbyte=testtext.getBytes();
System.out.println(testbyte);
testtext=new String(testbyte);
System.out.println(testtext);
System.out.println("nn");
//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();
}



}
}

我很感激任何帮助或提示！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。我不知道该补充什么。该代码通过"测试"系统输出，但也抛出一些异常。我希望你知道缺少什么，或者我必须添加什么才能使它发挥作用。

Answer 1

好吧，问题的直接原因是你忘记在ObjectOutputStream上调用这个方法(它关闭了包括CipherOutputStream在内的所有其他流(：

oos.close();

来自CipherOutputStream.close:的JavaDocs

此方法调用封装密码对象的doFinal方法，该方法将处理封装密码缓冲的任何字节。

因此，对于一些密码，flush可能会导致一些字节加密，但不会在末尾添加填充。

但还有很多其他事情也会引起悲伤：

1. 您没有指定应该使用哪种填充，所以在其他Java安装中可能会有所不同，请参阅以获取一些建议：JavaDoc for Cipher或例如这个问题
2. 如果对象变大了一点(或者使用了占用更多空间的不同填充(，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：这个问题建议使用对称密码(如AES(加密，而只使用RSA加密AES密钥。(或者将密钥大小增加一倍，并准备每次密钥大小增加7或8倍的CPU时间，请参阅：此问题以获取更多信息(
3. 您应该知道String.toBytes((和String(byte[](都使用默认编码，这在其他计算机上可能不同，请确保指定例如java.nio.charset.StandardCharSets.UTF_8

免费建议：如果你要将你的"Nachricht"(消息(交换到另一台计算机，并且想要真正安全、快速、简单(在一定程度上(和防傻的东西，我建议你使用TLS(或DTLS(，这是基于25年的研究和实践。