FPGA Central - World's 1st FPGA / CPLD Portal

FPGA Central

World's 1st FPGA Portal

 

Go Back   FPGA Groups > NewsGroup > FPGA

FPGA comp.arch.fpga newsgroup (usenet)

Reply
 
LinkBack Thread Tools Display Modes
  #1 (permalink)  
Old 11-14-2007, 02:23 PM
Amal
Guest
 
Posts: n/a
Default Xilinx Encrypted bit file

I know Xilinx keeps its bit file header format secret. But, does
anyone know how to detect if a bit file is encrypted or not? As part
of our manufacturing builds, we need to make sure the bit file we are
choosing, is the encrypted file and not the regular bit file.

Maybe someone knows how to read and de-cypher the XIlinx bit file
header. Or has a command-line tool to detect that.

Please let me know,
-- Amal

Reply With Quote
  #2 (permalink)  
Old 11-14-2007, 03:59 PM
austin
Guest
 
Posts: n/a
Default Re: Xilinx Encrypted bit file

Amal,

An unencrypted bit file is 3 to 7% 1's (97 to 93% 0's) typically.

An encrypted bit file is roughly 50% 1's and 0's.

Real easy to tell them apart.

Austin
Reply With Quote
  #3 (permalink)  
Old 11-14-2007, 06:46 PM
Symon
Guest
 
Posts: n/a
Default Re: Xilinx Encrypted bit file

"austin" <[email protected]> wrote in message
news:[email protected]
> Amal,
>
> An unencrypted bit file is 3 to 7% 1's (97 to 93% 0's) typically.
>
> An encrypted bit file is roughly 50% 1's and 0's.
>
> Real easy to tell them apart.
>
> Austin

Hi Austin,
What if the FPGA design had all the BRAMs initialised to 1's? ;-)
Cheers, Syms.


Reply With Quote
  #4 (permalink)  
Old 11-14-2007, 07:02 PM
austin
Guest
 
Posts: n/a
Default Re: Xilinx Encrypted bit file

Symon,

Even with all BRAM's to 1's, the files will still look really very
different in terms of one's density!

One of the side-effects on a good encryption method is that it makes the
data look like "noise."

So, what they need is a way to tell the difference between "noise" and a
unencrypted bit file.

You could play it through a sound card, and you could immediately tell
the difference, for example.

(I can see the assembly line taking 'dance to the bit stream breaks')

Or, you could display the bit file on a monitor with 24 bit color, in
..bmp format (or .tiff, or whatever) and the encrypted files will look
like grey splotches of many colored pixels, and the unencrypted bit
files will look like structures of some sorts (not "noise" at all!).

By the way, I use this last method to evaluate true random number
generators, as your brain can view a big (1760 X 1024 X 24 bit) picture
and almost instantly "see" non-random behavior ... must have something
to do with us all coming from hunters on the veld two million years ago ...

If you display them fast enough, you can even make a "movie" or if you
play them fast enough, a symphony.

Austin
Reply With Quote
  #5 (permalink)  
Old 11-14-2007, 09:43 PM
Symon
Guest
 
Posts: n/a
Default Re: Xilinx Encrypted bit file

"austin" <[email protected]> wrote in message
news:[email protected]
> Symon,
>
>
> You could play it through a sound card, and you could immediately tell
> the difference, for example.
>

Hi Austin,
That reminds me of the technician guys who can listen to PRBS patterns sent
over PCM channels and tell you which of several PRBS's it is. You're right,
the pattern matching of the brain is remarkable.
Cheers, Symon.


Reply With Quote
  #6 (permalink)  
Old 11-14-2007, 10:21 PM
austin
Guest
 
Posts: n/a
Default Re: Xilinx Encrypted bit file

Symon,

The 'sush-sush' of 2E20-1 is very easy to hear, as it repeats every ~.75
or ~.5 seconds (T1 or E1) so that was not such a remarkable feat!

And anything shorter (2E7-1) had audible tones that the tech could hear!

After all, a LFSR (linear feedback shift register) is a PRBS
(pseudo-random bit source) is only a PRNS (pseudo-random noise source),
and not really random at all.

Like any amazing feat, there is likely to be something simple behind it,
so that any idiot can do it.

Reminds me of what I saw on the news this morning, a fish market vendor
was asked about the ban on crab fishing in the SF bay area, and were SF
bay crabs really different?: her answer? "Grandpa Alioto swore that
they tasted better from the SF bay, but we snuck some from Washington
onto Mom's plate, and when told of what we had done, she said - never
could tell the difference really ... dad couldn't either."

Austin
Reply With Quote
  #7 (permalink)  
Old 11-15-2007, 04:52 AM
Matthieu
Guest
 
Posts: n/a
Default Re: Xilinx Encrypted bit file

To follow what said Austin, a side-effect caused by the contents of the
encrypted bit-file locking like noise is that the compression ratio of
the encrypted bit file will be near 1:1.

Therefore a practical solution regarding the problem of the OP would
consist in compressing all his BIT files in a single archive and then
sort the contents of the archive by compression ratio (or compressed size).

This however may not work if bitgen is called with the "Compress"
parameter...
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
The .vh file type vs Xilinx Daniel O'Connor Verilog 3 01-28-2007 03:38 AM
Xilinx' encrypted HPICE models in PSPICE Melanie Nasic FPGA 3 12-15-2005 06:56 PM
Xilinx ISE 7.1i file management cyd FPGA 1 10-06-2005 02:18 PM
Back Annotating encrypted netlists Paul Richardson Verilog 0 05-27-2004 08:13 PM
Preferred method of sending encrypted Verilog IP Edward Arthur Verilog 7 01-21-2004 06:22 PM


All times are GMT +1. The time now is 06:58 AM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.2.0
Copyright 2008 @ FPGA Central. All rights reserved