FileOutputStream w/ Cipher adds extra lines unnecessarily

[john price]

The following code seems prints to "login.encrypted" empty lines, then the value of "x". Does this do this on it's own or is another part of my 1.2k + lined program that is buggy?

skeySpec = new SecretKeySpec(filePass.getBytes("UTF-8"), "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
CipherOutputStream cos = new CipherOutputStream(new FileOutputStream("login.encrypted", true), cipher);
PrintWriter prt = new PrintWriter(new OutputStreamWriter(cos, "UTF-8"));
System.out.println(x); //this line prints out the correct value of "x"
prt.print(x); //this line prints several blank lines, then the value of "x"
//I have also tried the above line with "ln" with the same results
prt.close();

Thanks,
John Price

[Ireneusz Kordal]

I've tried your code, and I've got this content in the output file:

ľ˘-9aĐ7” ĎüÍߤŠŕU:Čn=Ą˜ĺěN@Óq

It seems to be encrypted, I don't see any empty lines in it.

[john price]

When I read the file back in, I see the empty lines. With CipherInputStream and a BufferedReader. I use this over my program in other places and don't see this issue until after it is written to, adding a line to the end (which adds the blank lines for some reason).

Thanks,
cc11rocks

[Paul Clapham]

But that is an entirely different question. Now you are saying that encryption followed by decryption causes extra lines to be added. Obviously there is the possibility that the decryption process is the problem. At any rate I'm sure the answer is that some part of your program is buggy.

However you don't have to debug 1200 lines of code. You just have to extract the encrypting and decrypting parts and put them into a 50-line test program.

[john price]

Here is the read in where the lines display extra lines. Note this does not happen if something hasn't been appended to the file.

Cipher cipher = Cipher.getInstance("AES");
	skeySpec = new SecretKeySpec(filePass.getBytes("UTF-8"), "AES");
	cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        CipherInputStream cis = new CipherInputStream(new FileInputStream("login.encrypted"), cipher);
        BufferedReader bufread = new BufferedReader(new InputStreamReader(cis, "UTF-8") );
        
        String line;
        while(null != ( line = bufread.readLine())){
        	System.out.println("914 : " + line);
            	String[] entry = line.split("&", 2);
            	knownUsers.put(entry[0], entry[1]);
        }
        bufread.close();

Output gives somthing like this :

914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 :
BLANK LINE ERROR

If I put in a test case, I get this :

Cipher cipher = Cipher.getInstance("AES");
	skeySpec = new SecretKeySpec(filePass.getBytes("UTF-8"), "AES");
	cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        CipherInputStream cis = new CipherInputStream(new FileInputStream("login.encrypted"), cipher);
        BufferedReader bufread = new BufferedReader(new InputStreamReader(cis, "UTF-8") );
        
        String line;
        while(null != ( line = bufread.readLine())){
        	System.out.println("914 : " + line);
            	String[] entry = line.split("&", 2);
            	try {
            	knownUsers.put(entry[0], entry[1]);
            	}
            	catch (Exception sxr) {sxr.printStackTrace();}
        }
        bufread.close();
	}
	catch (Exception afff) {afff.printStackTrace();}

Which displays this :

914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 : [entry&entry] //real output here
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
914 :
BLANK LINE ERROR
//more empty lines
//more blank line errors
914 : [entry&entry] //This is the correct registered line

Thanks,
John Price

[Ireneusz Kordal]

john price wrote:Here is the read in where the lines display extra lines. Note this does not happen if something hasn't been appended to the file.

Something is appended to the encrypted file ?
Does it mean, that something unencrypted has been appended to encrypted contents ?
If yes, then the problem is here - the encrypted file doesn't have
neither information of the content's size nor any checksum. The cipher doesn't detect the end of the encrypted output,
and it doesn't detect if contents has been modified.
It dencrypts the whole content - if something is appended to it,
it decrypts this part too.

[john price]

I was trying to append to the whole file. I was adding encrypted information to the file. I had to release the next version of a program so this is no longer a problem. I used a more efficient way by rewriting the whole file and adding the specific item to memory. Thanks for your help.

John Price