🚀 go-pugleaf

In article <wa6JsB7w165w@works.uucp> ferret@works.uucp (Dave Ferret) writes:
   Just a sidenote to 'Hackers' words...

     There are also encryption algorithms that when used to encrypt the 
   plaintext over and over and over, will yield the un-encrypted text. (Ie: 
   Its a circular encryption -- Sorry, I don't know the correct term here)

Cyclic, as in subgroup. The question is often phrased, "Is DES a
group?" (under composition of encryption). Last I read (Crypto '90?),
it was strongly suspected but not conclusively proven to contain no
cycles* (recall that a finite group must contain at least one cycle).
A common suggestion for using DES as a superencipherment for itself is
E_k1(D_k2(E_k1(P))), where E_k1 = encrypt with key k1, etc.  If
encrypting twice with the same key were a lot stronger than encrypting
once, then no doubt the algorithm would just do that (bearing
performance limits in mind, of course). If you get FIPS pub 46 (and
81) or an intrology to cryptoduction and read through the algorithm,
you will see that it already contains 16 rounds with key
transformations and that things get pretty messy in there :-)

   Also, the reasons for tinkerig with DES could possibly be for one reason, 
   it was claimed 'unreversable' (Right?) and also that its the basis for 
   Unix' CRYPT(). 

Eh? It is used in Unix password encryption to _create_ a one way
function -- a random 12-bit salt value is added in to the password,
then that is used as a key to encrypt a 64-bit constant 25 times. The
multiple encryption is not there to strengthen the algorithm as much
as to slow it down, to make dictionary attacks less feasible.

The account on pp. 30-31 of Garfinkel and Spafford, _Practical Unix 
Security_ (O'Reilly & Assoc., 1991) is brief and complete.

I'm sure this will be in the promised FAQ, either in all its 
gory detail or by reference to G&S or equivalent.

-- Craig Presson
* - here's a reference I haven't read yet, that should be definitive:
@inproceedings{campbell,
  author = "Campbell, K.W. and Wiener, M.J.", 
  year = 1993,
  title = "Proof that {DES} is not a group",
  booktitle = "Advances in Cryptology --- Crypto '92",
  publisher = "Springer-Verlag",
  address = "New York",
  note = "To appear"}
Note to me: call & see if this is out yet.