Random number generators

There seems to be some confusion over this random number device.

Perry Metzger forwarded me some information about Newbridge
Microsystems and the part number of a chip that made random numbers.
At the crypto BOF at hackers I mentioned that there was a need for a
hardware random number generator and that I knew of some chip to do
it.  John Draper, who was there, expressed a desire to work on such a
device.  I forwarded him the information about the chip.

What I didn't know was the cost or design of this chip.  It appears to
use a radioactive source to make random numbers.  This may account for
the cost.  In any case, it is likely that most applications don't need
this kind of chip.

What is needed, though, is _some_ kind of chip.  John Draper is eager
to manufacture such a device, once we have a design.  Would those
people willing to help on this design please get in touch with him
directly and start a conversation about it.  The conversation could
reasonably be discussed on the list, if enough are interested.

FYI, random numbers are used generally to create single-use session
keys in a wide variety of crypto protocols, including Diffie-Hellman
key exchange.  Hardware random number sources will be a standard
component of all computers in the near future.

As far as the design of the device itself goes, the numbers that come
out of it don't have to be fully random.  Non-randomness can be
corrected in software.  Two characteristics of the output, though will
help such correction.  First, the number of ones and zeros should be
the same.  Not only is this useful for correction, but it is easy to
do in hardware.  Second, effort should be made to make sure that the
generator does not pick up cyclic noise from its environment.  This
means attention to coupling, shielding, and packaging.  No extra
expense, likely, but definitely to be thought about some.

Eric

>From: Eric Hughes <hughes@soda.berkeley.edu>

>There seems to be some confusion over this random number device.

>Perry Metzger forwarded me some information about Newbridge
>Microsystems and the part number of a chip that made random numbers.
>At the crypto BOF at hackers I mentioned that there was a need for a
>hardware random number generator and that I knew of some chip to do
>it.  John Draper, who was there, expressed a desire to work on such a
>device.  I forwarded him the information about the chip.

>What I didn't know was the cost or design of this chip.  It appears to
>use a radioactive source to make random numbers.  This may account for
>the cost.  In any case, it is likely that most applications don't need
>this kind of chip.

Just for the record...
As the data sheet makes clear, it most certainly DOES NOT use a
radioactive source. Its very hard to get 20kbits/sec of random numbers
reliably out of any radioactive source you are going to want to be
near, anyway. It operates off of thermal noise just like virtually
every other such device.

It should be possible to build a similar device out of ordinary
discrete components without overwhelming difficulty. The only problem
would be to make sure that the output was reliably random, and not
overly dependant on things like temperature.

Perry

Eric Hughes comments and then Perry Metzger responds:

> >Perry Metzger forwarded me some information about Newbridge
> >Microsystems and the part number of a chip that made random numbers.
> >At the crypto BOF at hackers I mentioned that there was a need for a
> >hardware random number generator and that I knew of some chip to do
> >it.  John Draper, who was there, expressed a desire to work on such a
> >device.  I forwarded him the information about the chip.
> 
> >What I didn't know was the cost or design of this chip.  It appears to
> >use a radioactive source to make random numbers.  This may account for
> >the cost.  In any case, it is likely that most applications don't need
> >this kind of chip.
> 
> Just for the record...
> As the data sheet makes clear, it most certainly DOES NOT use a
> radioactive source. Its very hard to get 20kbits/sec of random numbers
> reliably out of any radioactive source you are going to want to be
> near, anyway. It operates off of thermal noise just like virtually
> every other such device.
> 
> It should be possible to build a similar device out of ordinary
> discrete components without overwhelming difficulty. The only problem
> would be to make sure that the output was reliably random, and not
> overly dependant on things like temperature.
> 
> Perry

Perry is correct. Getting 10K or more bits per second from a
radioactive soure usually means it is close enough/strong enough to
"drift" the device to the point of radiation-induced permanent failure
in a matter of weeks or months (if not much sooner, but this is all so
dependent on exact calculations and lab experiments).

Tony Patti, editor of a small crypto journal and frequent commentator
on sci.crypt, is one of several folks who've designed thermal
noise-based RNGs. He's selling them, as I recall. I would _strongly_
advise anyone who's contemplating building and selling such a gizmo to
first see what the market has produced and whether or not it's
selling, etc.

A minor note: the bias between 0s and 1s (unequal distribution, for
example) is easily handled by considering pairs of numbers, with a "0
1" being called a "0" and a "1 0" being called a "1." 

--Tim


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