From: Erik.Lindano@ofa123.fidonet.org
Newsgroups: sci.crypt
Subject: New Encryption System - Challenge!
Date: 7 Nov 92 04:17:34 GMT
X-Sender: newtout 0.02 Nov  5 1992

Seeing that there are many capable cryptanalysts here, adept at 
 decrypting various sorts of scrambling, encryption and passwords, 
 I'd like to pose a question and ask for some help.
  
 A person has approached me and said he has devised an unusual 
 encryption method.  He showed me an MS DOS program that encrypts and 
 decrypts files in a way that I cannot fathom - but then I am no 
 expert, so that's no surprise.  However, to prove to me the value of 
 his encryption method, he has suggested a series of challenges, and 
 I'd like to present them here for discussion.  Let's call his new 
 encryption method `NuCrypt' for the sake of brevity.  Right now, 
 NuCrypt is a secret program, but I'm allowed to say that it is a 
 very short program which encrypts extremely fast.  No huge prime 
 numbers or anything... the author don't know nothin' 'bout prime 
 nummers, he says...  
  
 One of the challenges he's proposed goes like this:
  
    1. Almost all the contents of a 200-word English plaintext file 
       are disclosed. Somewhere in the midst of the English text, 
       however, there are two or three words, of 8 characters or less 
       each, represented only by "--------". These words are not 
       disclosed. They, too, are common English words and are valid 
       in the context they're in.
        
    2. Ten identical copies of the above text file, including the 
       two/three undisclosed words, are encrypted with NuCrypt.  Each 
       copy is encrypted only once.  Each time, NuCrypt produces an 
       encrypted version of the file.  Each ciphertext example is 
       different from the others. (NuCrypt itself doesn't change, nor 
       does it create any "key" files or any other output except the 
       ciphertext and a brief screen message announcing completion.)  
       In creating ciphertext, NuCrypt may use all 255 ASCII 
       characters, even if the plaintext did not.  Each of these 
       encrypted files can be quickly and correctly decrypted using 
       the same or another copy of NuCrypt.  As usual, the ciphertext 
       has a more or less random appearance and is pretty much 
       incompressible by archiving utilities.
        
    3. The entire English plaintext (minus the actual 2 or 3 non- 
       disclosed words), as well as all 10 NuCrypt-encrypted 
       examples, are made public.
        
    4. The NuCrypt program itself, used to perform the encryption and 
       decryption, is not disclosed.
     
 Will anyone here accept the challenge to discover the secret words? 
 Is it deemed an easy task?  A trivial task?  A difficult task?  An 
 impossible task? 
  
 Another challenge he proposed goes like this:
  
     1. A 1-10 kB plaintext file consisting almost entirely of a 
        simple series of Zeroes, or of any other character, or _any_ 
        other pattern of your choice, including numerical 
        progressions, the Latin alphabet, etc., etc., has ONE single 
        non-disclosed word in its midst.  This ONE word is identified 
        in the plaintext only as "xxxxxxxx".  The rest of the file is 
        fully disclosed and can be nearly anything you want.
         
     2. NuCrypt is used to encrypt 10 (or any other reasonable number 
        of) identical copies of the plaintext, including the non- 
        disclosed word. (The non-disclosed word remains always the 
        same in all 10 copies of the plaintext being encrypted.)  
        Each of these encrypted files may be readily decrypted with 
        NuCrypt to yield the correct original plaintext. Again, no 
        output other than the ciphertext is created, etc. and again, 
        the ciphertext may employ any of the 255 ASCII characters 
        even if the plaintext did not.
         
     3. Both the plaintext and all 10 encrypted files are published.
         
     4. The NuCrypt program itself is not disclosed.
         
 Based on such materials, can anyone actually decrypt that ONE, non- 
 disclosed word?  Is it easy to do? Trivial? Difficult? Impossible? 
  
 If anyone is interested, I can post both the plaintext and the 
 encrypted examples here. To insure fairness, copies of the plaintext 
 files with the non-disclosed words can be deposited with some 
 neutral and mutually-trusted party, and examined afterwards.  Make a 
 suggestion.
  
 My acquaintance likes to think no one can defeat his cipher.  He 
 further states that if anyone feels that the above examples are not 
 fair or adequate, then the readers here are free to suggest their 
 own rules, test methods and materials.
  
 Personally, I think cracking this thing should be pea soup for the 
 capable cryptologists here.  Which one of us is right?  There are 
 no "tricks" in the preparation of the plaintext files or in making 
 copies of them.  All plaintext copies are identical.  Each 
 ciphertext is fully reversible to plaintext by means of the NuCrypt 
 program running under MS DOS, without any kind of preparation or 
 manipulation (except the retention of a characteristic filename 
 extension, always the same, which is used by the program to 
 recognize the scrambled file as one produced by itself.)
  
 Apart from the intellectual challenge, the author of NuCrypt says 

--- Maximus 2.00