From: Eric Fogleman <Eric.Fogleman@analog.com>
Date: Wed, 27 Jan 93 14:51:10 PST
To: thug@phantom.com
Subject: Limiting "white" noise runlength
Message-ID: <9301272248.AA18636@ack.adstest.analog.com>
MIME-Version: 1.0
Content-Type: text/plain


Mr. Thug,

In talking about "white" noise, you mentioned:

> Yes I do think the idea of making a "more random than random" stream
> by filtering out long runs of 0's or 1's weakens the the key stream
> in theory, but in practical use it strengthens it, because if the stream
> is left alone, runs of 500 bits of 0's or 1's can come through, and any
> fool can then extract plain text using XOR in this area of the cyphertext.
> LZW compression of the plaintext helps, but I feel that it is far better
> to reduce the possibility of a key stream containing long runs of 0's or
> 1's, than to leave it alone.

Why not feed back the previously encrypted bits to perform the
"present" encryption (something like cipher block chaining) to keep
this from happening?  Then any particular encrypted character will
depend on *all* previous characters and break up runs of "plaintext".
That seems much better than un-whitening your white noise...

Eric Fogleman