Re: encrypted FM radio hiss

[David Honig <honig@m7.sprynet.com>]

At 10:40 AM 7/28/98 +0100, Mok-Kong Shen wrote:
>David Honig wrote:
>
>> The output of a good block cipher in feedback mode will pass Diehard tests,
>> though it is not crypto-secure.
>
>I often see the phrase 'pass Diehard test' though I don't see from
>the documents of Diehard how to evaluate the volumenous printout
>of Diehard to say exactly whether the test is passed or not. Furthermore
>the component asc2bin.exe of Diehard is buggy.
>
>M. K. Shen
>

My rough understanding: the 'P' value is a measure on the hypothesis that
the test sample is a truly random sample, where truly random is defined by
the expected 
statistical properties being measured.  Eg in 100 bits you expect to find
50 1's; 
if you count 48, is your 100-bit sample consistant with it being
unpredictable?

If you get values near 1.0 your sample is not likely taken from a random pool.


Try this: generate 10Meg from a block cipher feeding back on itself.  Diehard
will pass these.  (Diehard needs 10M samples)

Now run FM hiss into your soundcard.  Sample this at 8Khz (to avoid
temporal correlation)
and save to a file til you have 10Meg.  Diehard will reject this.  Make a
larger
file, and then gzip it down to 10Meg.  (That it shrinks indicates its symbols
don't carry a full bit.)  Run Diehard on this.  It will pass more tests but
not all.


Take the FM hiss, feed it into a stream cipher, and start burning those OTPs.


Do this with a detuned *video* tuner for more bandwidth. 








honig@alum.mit.edu

   "Speech is not protected simply because it is written in a language"	
	Federal Misjudge Gwin on the Bernstein Case