From: tcmay@netcom.com (Timothy C. May)
Date: Fri, 29 Jan 93 10:29:42 PST
To: cypherpunks@toad.com
Subject: Re: OTP Generators
Message-ID: <9301291826.AA15886@netcom3.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



Hal Finney writes:

> Douglas Sinclair asked about the earlier discussion re the use of 
> radiation to generate true random numbers for one time pads.
> 
> The problem, as I recall, was with the quantity of bits needed.  OTP's 
...stuff elided...
> So, the needed particle emission rate is 40,000 divided by the 
> efficiency of your detector.  Perhaps Douglas could get some efficiency 
> figures from his father, and judge whether this rate of radiation 
> emission would be safe.

Yes, we've discussed this a couple of times.

For a 2 pi detector geometry, about 100,000 decays per second are
needed to give the 40,000 or so that the detector could see. This is
about 3 microcuries (1 curie = 3.7 x 10^10 disintegrations per
second), which is far higher than the Am-241 smoke detector sources
have (0.1 microcurie, if I remember correctly...but I could be wrong
on this, as it's been years...).

(There's also the issue of detector drift, with such high levels
causing changes in the detector properties.)

Obviously, multiple detectors could be used, each generating perhaps
several thousand bits pers second. It'll still take a week or so to
fill a single CD-ROM.

Not too practical. Nor is the production and distribution of CD-ROMS
very convenient. Using this for "Cypherpunks"-type activities would be
a nightmare of inconvenience for all concerned.

-Tim



-- 
..........................................................................
Timothy C. May         | Crypto Anarchy: encryption, digital money,  
tcmay@netcom.com       | anonymous networks, digital pseudonyms, zero
408-688-5409           | knowledge, reputations, information markets, 
W.A.S.T.E.: Aptos, CA  | black markets, collapse of governments.
Higher Power: 2^756839 | Public Key: waiting for the dust to settle.



-- 
..........................................................................
Timothy C. May         | Crypto Anarchy: encryption, digital money,  
tcmay@netcom.com       | anonymous networks, digital pseudonyms, zero
408-688-5409           | knowledge, reputations, information markets, 
W.A.S.T.E.: Aptos, CA  | black markets, collapse of governments.
Higher Power: 2^756839 | Public Key: waiting for the dust to settle.