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From: Rich <rich@example.invalid>
Newsgroups: sci.crypt
Subject: Re: Naive PRNG encryption?
Date: Sat, 3 Aug 2024 20:00:36 -0000 (UTC)
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vallor <vallor@cultnix.org> wrote:
> I saw someone mention this on another 'froup, and I've thought about it 
> myself.  Is it really "uncrackable"?
> 
> Take a plaintext and transform each character with the output
> of a PRNG, with the seed being the key.

https://web.pa.msu.edu/reference/pgpdoc1.html

   When I was in college in the early seventies, I devised what I 
   believed was a brilliant encryption scheme.  A simple pseudorandom 
   number stream was added to the plaintext stream to create 
   ciphertext.  This would seemingly thwart any frequency analysis of 
   the ciphertext, and would be uncrackable even to the most 
   resourceful Government intelligence agencies.  I felt so smug about 
   my achievement.  So cock-sure.

   Years later, I discovered this same scheme in several introductory 
   cryptography texts and tutorial papers.  How nice.  Other 
   cryptographers had thought of the same scheme.  Unfortunately, the 
   scheme was presented as a simple homework assignment on how to use 
   elementary cryptanalytic techniques to trivially crack it.  So much for 
   my brilliant scheme.