From: "James A. Donald" <jamesd@echeque.com>
Date: Thu, 9 Nov 1995 14:39:05 +0800
To: Raph Levien <loki@obscura.com>
Subject: Re: PGP Comment feature weakens remailer security
Message-ID: <199511090618.WAA21037@blob.best.net>
MIME-Version: 1.0
Content-Type: text/plain


At 05:47 PM 11/8/95 -0800, Raph Levien wrote:
> So let me rephrase the question: what's the minimum number of entropy
> bits that can be used and still give you that warm and fuzzy feeling
> that you don't have to worry about the possibility that the message
> might be corrupted?

I guess that if comet hits the earth and exterminates the human race
you would not be unduly worried by a corrupted message, so let us make
the odds equal to human civilization being destroyed on the same day.

We get roughly one massive extinction every hundred million years, or 
so and a smaller blast that would demolish our technology every ten 
million years or

So the probability of an error was equal to the human race and most
major species being destroyed the same day, you would not be unduly 
worried.

Probability of human civilization and all large animals being wiped out
by comet impact tonight is 2.7E-11, so thirty five bits should be 
sufficient.

But, if you want to feel really comfortable, make it forty bits.

The probability of hitting a forty bit combination by chance is
equal to the probability that all large animals on earth will
be wiped out by comet impact in the next three quarters of an hour.

But you might have a million lines, and send a million messages,
each of a million lines.

So let us make the probability that one of those fails equal to
the chance that all large animals on earth get wiped out in the next
half hour.

Well in that case make it eighty bits.

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