Xref: utzoo rec.ham-radio:4628 sci.crypt:1026
Newsgroups: rec.ham-radio,sci.crypt
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Understanding scrambled speech without a descrambler
Message-ID: <1988Apr20.075217.761@utzoo.uucp>
Organization: U of Toronto Zoology
References: <2760@ihuxz.ATT.COM>
Date: Wed, 20 Apr 88 07:52:17 GMT

>    One of my favorite daydreaming topics is how humans might
>    develop  the  ability  to  understand  scrambled  speech,
>    without using a  descrambler...

There are instances of this on the record.  In mid-WW2, Bell Labs
demonstrated that about half of a conversation using the then-current
A-3 scrambler -- used by Roosevelt and Churchill, among others --
could be understood by the unaided ear, with some practice.  It is
really quite hard to scramble speech well with pre-digital techniques.
There is too much redundancy in it.

(For more detail, see Kahn's 'The Codebreakers'.)
-- 
"Noalias must go.  This is           |  Henry Spencer @ U of Toronto Zoology
non-negotiable."  --DMR              | {ihnp4,decvax,uunet!mnetor}!utzoo!henry