Encryption using DES

> > You probably didn't realize that DES works on

> bytes,

> > not chars, and corrupted your data by using

> Readers

> > and Writers on it. Stick to InputStreams and

> > OutputStreams.

>

>

> Which I did

> it works ok with text file

> but using word document file the bites are in

> different bit sizes some are 32 bits DES uses 64

> bit for encryption.

> If we have 3 MBytes then it would take very

> lOOOOOOOOOOOOng time to encrypt or decrypt.

>

> any idea on how to Optimise

>

I don't understand what you mean by "the bites are in different bit sizes some are 32 bits DES uses 64 bit for encryption". What do you mean by 'bites'?

Unless you are trying to DES encrypt a byte a a time, I can't imagine what you can be doing to take a long time. It takes less than a second for me to DES encrypt a 3MByte file using the JCE.

Post your code!

sabre150a at 2007-7-10 12:13:19 >

> For almost all practical purposes a "byte" means

> "eight bits". Certainly that applies here.

>

> A Word document is just a collection of eight bit

> values (bytes). If your code is treating a Word

> document differently from any other file then your

> code is wrong.

Sorry I ment to say byte

however , I have read some bytes from the file in byte []bt array

using the following

// find out howmany bits in every byte

for ( int n = 0 ; n < bt.length ; n++){

int v = bt[n] ;

String binstr = Integer.toBinaryString(v);

System.out.print ("\n" + new String(binstr) + "{ # bits is : "+ binstr.length()+" }");

}

And that what I have

THE NUMBER OF BYTES IN THE FILE IS >>> : 24064

11111111111111111111111111010000{ # bits is : 32 }

11111111111111111111111111001111{ # bits is : 32 }

10001{ # bits is : 5 }

11111111111111111111111111100000{ # bits is : 32 }

11111111111111111111111110100001{ # bits is : 32 }

11111111111111111111111110110001{ # bits is : 32 }

11010{ # bits is : 5 }

11111111111111111111111111100001{ # bits is : 32 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

0{ # bits is : 1 }

111110{ # bits is : 6 }

0{ # bits is : 1 }

11{ # bits is : 2 }

0{ # bits is : 1 }

11111111111111111111111111111110{ # bits is : 32 }

11111111111111111111111111111111{ # bits is : 32 }

1001{ # bits is : 4 }

0{ # bits is : 1 }

//Appending '0'to byte ? to make it to 32 bits ?

B747newa at 2007-7-10 12:13:19 >

> And that what I have

What you're looking at isn't bytes. As I said before, a byte is eight bits. It's always eight bits. If it's not eight bits then it's not a byte.

And what you're looking at are integers.

What's happening here is that you're converting bytes (eight bit values) to integers (signed 32 bit values) and then converting those into a String representing the bit values of the integer.

That doesn't print leading zeros for exactly the same reason that we would write 42 instead of 000042. The values with large numbers of leading ones are because you're converting an arbitrary byte value into a negative integer (if the first bit of the byte is set the integer conversion treats it as a negative value).

I think you've bitten off more than you can chew with this DES stuff. You need to study the basics in a bit more depth.

dcmintera at 2007-7-10 12:13:19 >