How to generate and use variables in different switch statements

YellowMoon · January 29th, 2012, 03:05 AM

I'm trying to encrypt a text with DES algorithm using Bouncy Castle library. I have written the following code:

Code:

    	
    	try{
     		KeyGenerator kg=KeyGenerator.getInstance("DES");
     		SecretKey key=kg.generateKey();
     		SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "DES");
     		Cipher cipher=Cipher.getInstance("DES");
    	}catch(Exception e)
    	{
    		
    	}
    	
    	  	
    	switch(selection){
    	
    	case enc:
    		try{
    			
    			cipher.init(Cipher.ENCRYPT_MODE, keySpec);
    			String inText=inputText.toString();
    			byte[] cipherText=cipher.doFinal(inText.getBytes());
    			encText.setText(new String(cipherText));
    		}catch(Exception e)
			{
			encText.setText("Exception occured!");	
			}
    		break;
    		
    	case dec:
    		try{
    			cipher.init(Cipher.DECRYPT_MODE, keySpec);
    			String encT=encText.toString();
    			byte[] decBytes=cipher.doFinal(encT.getBytes());
    			decText.setText(new String(decBytes));
    		}catch(Exception e)
			{
			decText.setText("Exception occured!");	
			}
    		break;
    	}
    }

The code is supposed to work as follows: The following part of the code will generate "keySpec" and "Cipher" which is used in both encryption and decryption parts in the switch statement.

Code:

try{
     		KeyGenerator kg=KeyGenerator.getInstance("DES");
     		SecretKey key=kg.generateKey();
     		SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "DES");
     		Cipher cipher=Cipher.getInstance("DES");
    	}catch(Exception e)
    	{

Then depending on the user selection, inputText is encrypted or encText is decrypted in the switch statement. Both encryption and decryption blocks share the same "keySpec" and "Cipher" variables generated in the above code snippet. However, the compiler says that keySpec and Cipher cannot be resolved which I understand is that the keySpec and Cipher generated cannot be seen by the statements inside the switch blocks. How can I make it work?

Cheers,

BobPaul · January 29th, 2012, 07:37 AM

The variables in your try block are out of scope by the time
you get to the switch statements.

Move your switch statements into the try block OR make another block that surrounds everything and move the definition of your variable there.

I'd chose the first approach, try/catch blocks are good.

PS: This is not an Android question by the way.

Sam Voss · January 29th, 2012, 10:15 AM

Try putting:

Code:

Cipher cipher;
SecretKeySpec spec;

Above the onCreate method, allow its scope to greaten, then just initialize the code within the methods.

Sam Voss · January 29th, 2012, 10:17 AM

Quote:

Originally Posted by BobPaul

The variables in your try block are out of scope by the time
you get to the switch statements.

Move your switch statements into the try block OR make another block that surrounds everything and move the definition of your variable there.

I'd chose the first approach, try/catch blocks are good.

PS: This is not an Android question by the way.

Even though this is a Java question, its still an android question

YellowMoon · January 30th, 2012, 05:28 AM

Thanks for your replies, I'll try these and write the result here...

YellowMoon · January 31st, 2012, 07:50 AM

Thanks, it worked.

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