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1992-10-26 - entropy

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From: Eric Hughes <hughes@soda.berkeley.edu>
To: cypherpunks@toad.com
Message Hash: 372c96cffd382696c685f18f23b0868ec033ccb4cd1e33b39fcededb8cc5f91d
Message ID: <9210261653.AA13072@soda.berkeley.edu>
Reply To: <921024155350_74076.1041_DHJ67-1@CompuServe.COM>
UTC Datetime: 1992-10-26 16:53:38 UTC
Raw Date: Mon, 26 Oct 92 09:53:38 PPE

Raw message

{% raw  %}From: Eric Hughes <hughes@soda.berkeley.edu>
Date: Mon, 26 Oct 92 09:53:38 PPE
To: cypherpunks@toad.com
Subject: entropy
In-Reply-To: <921024155350_74076.1041_DHJ67-1@CompuServe.COM>
Message-ID: <9210261653.AA13072@soda.berkeley.edu>
MIME-Version: 1.0
Content-Type: text/plain


Hal:
>Ascii encoding used by PGP reduces this to 6 bits per character
>(e.g. a character set with 64 printable characters) neglecting
>line separators and message beginnings and endings.  So there
>should be a little less than 6 bits per character for encrypted,
>Ascii-encoded messages.

Hal is, of course, right.  I was getting myself confused between
entropy lost in the encoding and the entropy of the encoding.  The
channel uses up two bits of entropy per character in the encoding.
What's left is six bits.

As punishment for getting this so egregiously wrong, I'm going to post
some C code for measuring entropy so that you all can play with it.

Eric




{% endraw %}

Thread

• Return to October 1992

• 1992-10-24 (Sat, 24 Oct 92 09:02:41 PDT) - Multiple messages + entropy - Hal <74076.1041@CompuServe.COM>

  • 1992-10-26 (Mon, 26 Oct 92 09:53:38 PPE) - entropy - Eric Hughes <hughes@soda.berkeley.edu>