From: Jim choate <ravage@bga.com>
Date: Sun, 19 Jun 94 08:03:58 PDT
To: pfarrell@netcom.com (Pat Farrell)
Subject: Re: your mail
In-Reply-To: <199406182254.PAA22537@netcom3.netcom.com>
Message-ID: <199406191503.KAA01497@zoom.bga.com>
MIME-Version: 1.0
Content-Type: text


> 
> The Prime Assumption: White noise due to molecular motion is truly random.  
> Noise generated in a carbon resistor or zener diode is white noise.  
> 
> Is this true, cryptographically speaking?
>
What you want is a Gunn diode oscillator w/ feedback.

> 1.A a device would use a cheap noisy carbon resistor and a
> rude, crude, noisy amplifier to amplify the noise generated 
> by the resistor.  
>
Just remember to keep the temperature of the devices constant, semi-
conductors have a temperature dependancy which would allow them to monitor
the data and  possibly determine the gain of the amp and hence approx.
how much noise energy and sprectrum thereof it was contributing. Check
into Boltzmanns Constant applications to black body radiation.

> 1.B. A zener diode may make a "louder" noise and require a cheaper 
> amplifier.
>
I am not shure that a zener would produce any more  noise than a standard
diode. 
              
There might even be less noise because the design parameters are more tightly
controlled on a zener than standard diodes.

> 1.C How about if we take the hiss that you find between stations on an 
> FM receiver, and digitize them through a PC soundcard? 
>
I actually like this idea a lot.                                  

> that nobody wants to put 9 volt batteries in this thing and 
> have to remember to turn it off when they are finished using 
> their computers.   
>
How about using the lines on the serial port for power?

> should it  contain a switch to cut it in and out as needed and 
> free up the port? This sounds like an A-B switch. 
>
How about a dongle? 

> 
> 4. How secure should the device itself be? Bruce's wonderful _Applied 
> Cryptography_ talks about OS Virtual Memory managers writing out keys 
> to disk without the user/programmer knowing, which is a serious 
> potential problem. We have that same problem with the random number 
> that this device generates. Wose, it wouldn't be hard for a `bad guy' 
> to write a TSR that constantly reads the random port, and records
> the numbers in parallel with whatever wants to use it for real. 
>
If they have this close access to your hardware then you have a more 
serious problem.

> While I'd like to think that I really control my PC, once you get 
> networking TSRs, smartdrv, APSI drivers, CDROM and Soundcard drivers, 
> HIMEM, etc. loaded, do you really _know_ that they are your friends? 
> Is this a real problem?
>
I would suggest getting some of virus source out there and take a look
at how the detectors watch system activity for fishy writes. Should not
be hard to load another TSR which watchdogs the system for any bogus
or un-authorized reads from the device. Just pass all system calls through
the TSR to access the device.