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From: "Karl.Frank" <Karl.Frank@Freecx.co.uk>
Newsgroups: sci.crypt,comp.lang.java.programmer
Subject: Re: Why is Java 7 converting the Password toCharArray instead of Byte in it's PBKDF2 function?
Date: Tue, 19 Jun 2018 23:23:09 +0200
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On 19.06.18 22:18, Lothar Kimmeringer wrote:
> Karl.Frank wrote:
>
>> The amount of byte to read is exactly defined by
>>
>>     int BuffSize = System.in.available();
>>     byte[] pwByte = new byte[BuffSize];
>>     System.in.read(pwByte, 0, BuffSize);
>>
>> How would the program read more byte than necessary?
>
> InputStream.available only returns the number of bytes that
> can be read without blocking. Dependent on how the data ends
> up there there still might be data left to read that you
> missed because of that.
>
> What you're doing here is a common programming error.
>
>
> Cheers, Lothar

Well, well, well. The posted listing is just a short test program in
order to figure out why the results of the Java function were wrong.
It clearly does not expext a huge file being passed over by stdin.

Obviously in a program that need to handle large scale data one would
read in the data byte in chunks and process them subsequently like in
this short snipped


---------------------------------------8<----------

   int BuffSize = 8192;

   byte[] inByte  = new byte[BuffSize];
   byte[] outByte = new byte[BuffSize];

   int inB, outB, bufferRead;

   System.in.flush();
   System.out.flush();

   while ((bufferRead = System.in.read(inByte, 0, BuffSize)) != -1) {
     for (int i=0; i<bufferRead; i++){
       /*
         do something useful here
         for example XOR the byte

         inB  = (int)inByte[i];
         outB = (inB ^ *some CSPRNG byte output*) & 0xff;
         outByte[i] = (byte)outB;

         or similar...
       */
     }
     System.out.write(outByte, 0, bufferRead);
   }

   System.in.flush();
   System.out.flush();

   System.in.close();
   System.out.close();

--------------------------------------->8----------

So nothing to be worried about in regards of any unprocessed data left ;-)

Cheers,
Karl


-- 
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