SSL/TLS passive sniffing

[John Denker]

I wrote:

 >>If the problem is a shortage of random bits, get more random bits!

Florian Weimer responded:
> 
> We are talking about a stream of several kilobits per second on a busy
> server (with suitable mailing lists, of course).  This is impossible
> to obtain without special hardware.

Not very special, as I explained:

>>Almost every computer sold on the mass market these days has a sound
>>system built in. That can be used to generate industrial-strength
>>randomness at rates more than sufficient for the applications we're
>>talking about.  
> 
> How many bits per second can you produce using an off-the-shelf sound
> card?  Your paper gives a number in excess of 14 kbps, if I read it
> correctly, which is surprisingly high.

1) You read it correctly.
   http://www.av8n.com/turbid/paper/turbid.htm#tab-soundcards

2) The exact number depends on details of your soundcard.  14kbits/sec
was obtained from a plain-vanilla commercial-off-the-shelf desktop
system with AC'97 audio.  You can of course do worse if you try (e.g.
Creative Labs products) but it is easy to do quite a bit better.
I obtained in excess of 70kbits/sec using an IBM laptop mgfd in
1998.

3) Why should this be surprising?

> It's an interesting approach, but for a mail server which mainly sends
> to servers with self-signed certificates, it's overkill.  

Let's see....
  -- Cost = zero.
  -- Quality = more than enough.
  -- Throughput = more than enough.

I see no reason why I should apologize for that.

> Debian also
> supports a few architectures for which sound cards are hard to obtain.
> And we would separate desktop and server implementations because the
> sound card is used on desktops.  I'd rather sacrifice forward secrecy
> than to add such complexity.

As the proverb says, no matter what you're trying to do, you can always
do it wrong.  If you go looking for potholes, you can always find a
pothole to fall into if you want.

But if you're serious about solving the problem, just go solve the
problem.  It is eminently solvable;  no sacrifices required.


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