RC4算法的KeyGenerator异常

Question

The code is very easy and clear, but it throws exception at

KeyGenerator keyGen = KeyGenerator.getInstance("RC4");

and

Cipher aesCipher = Cipher.getInstance("RC4");

the exception is : unreported exception java.security.NoSuchAlgorithmException; must be caught or declared to be thrown

import java.io.*;
import java.security.*;
import javax.crypto.*;
import sun.misc.BASE64Encoder;


public class RCCC4 {
public static void main(String[] args) {
    String strDataToEncrypt = new String();
    String strCipherText = new String();
    String strDecryptedText = new String();

    try{ 
    KeyGenerator keyGen = KeyGenerator.getInstance("RC4");
    SecretKey secretKey = keyGen.generateKey();
    Cipher aesCipher = Cipher.getInstance("RC4");
    aesCipher.init(Cipher.ENCRYPT_MODE,secretKey);
    strDataToEncrypt = "Hello World of Encryption using RC4 ";
    byte[] byteDataToEncrypt = strDataToEncrypt.getBytes();
    byte[] byteCipherText = aesCipher.doFinal(byteDataToEncrypt); 
    strCipherText = new BASE64Encoder().encode(byteCipherText);
    System.out.println("Cipher Text generated using RC4 is " +strCipherText);
    aesCipher.init(Cipher.DECRYPT_MODE,secretKey,aesCipher.getParameters());
    byte[] byteDecryptedText = aesCipher.doFinal(byteCipherText);
    strDecryptedText = new String(byteDecryptedText);
    System.out.println(" Decrypted Text message is " +strDecryptedText);
    }
    catch (NoSuchPaddingException noSuchPad)
        {
            System.out.println(" No Such Padding exists " + noSuchPad);
        }

    catch (InvalidKeyException invalidKey)
        {
                System.out.println(" Invalid Key " + invalidKey);
        }

    catch (BadPaddingException badPadding)
        {
                System.out.println(" Bad Padding " + badPadding);
        }

    catch (IllegalBlockSizeException illegalBlockSize)
        {
                System.out.println(" Illegal Block Size " + illegalBlockSize);
        }

    catch (InvalidAlgorithmParameterException invalidParam)
        {
                System.out.println(" Invalid Parameter " + invalidParam);
        }

}
   }

Answer 1

The code works and is okay as it stands, you just need to add one more catch to catch NoSuchAlgorithmException - which won't ever occur in your program.

Because the algorithm name is passed as a String, the method getInstance() could possibly throw NoSuchAlgorithmException when the name was wrong. It just wouldn't know what to do with an unknown algorithm. This is not your case, but the compiler has to be sure to be happy.

Answer 2

实际上，通过此链接可以告诉您KeyGenerator确实支持RC4，但是将“ ARCFOUR”指定为算法名称

Answer 3

在这里尝试使用ARCFOUR代替RC4 文档

Answer 4

You'll have to do your homework yourself (please mark the question as such btw.) but here's a hint on the exception:

A java.security.NoSuchAlgorithmException means that the algorithm you want to use (RC4 in your case) is not supported on that machine. That might either be due to a typo (the name might be rc4 or something else) or the algorithm isn't provided out-of-the-box and you'd have to implement/add it yourself (which I assume is the case here).

Answer 5

You just need to catch this exception as well for it to work out....

catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }