🚀 go-pugleaf

In article <TTR0sB1w164w@jwt.UUCP> bbs-hrick@jwt.UUCP (Rick Harrison) writes:

   I've noticed that all the discussion of computerized cryptography
   seems to assume that one should use a byte-by-byte approach, i.e.
   take one byte of plaintext, encrypt it, output it, and repeat.

**ER0040B9E, Premises Check**
DES would be the most commonly-used counterexample, there are many
other generally similar systems that deal with blocks of plaintext
larger than a byte, and in fact can "chain" blocks so that the
constants used in encrypting block n are a function of the ciphertext
of block n-1.

   Wouldn't it also be possible and perhaps desirable to automate
   other approaches, such as a word-by-word approach? [...]
   How secure would such a scheme be?

You have just described a codebook, basically. Even with
superencipherment, this kind of thing is, practically speaking,
breakable at least partly, if you have enough intercepts to work from,
and in the real world there usually are.

Of course, the quickest way to compromise a codebook is to steal one
and copy it, but if you get caught you're back to square one, since
the code will be promptly changed. For the best collection of crypto
war stories, see David Kahn, _The Codebreakers_, 1967. It also covers
the technical history of cryptosystems up through the middle sixties,
and gives a lot of insight into the process of cryptanalysis. In fact,
I nominate Kahn for whatever prizes history-of-science books are
eligible for that he didn't already win.

qoxodboxopqoxodboxopqoxodboxopqoxodboxopqoxodboxopqoxodboxop
q    Craig Presson              pressonc@ingr.com          p
q    Intergraph Corporation             MS GD3005          p
q    Huntsville, AL 35894-0001     (205) 730-3885          p
q                          FAX:    (205) 730-9511          p
qoxodboxopqoxodboxopqoxodboxopqoxodboxopqoxodboxopqoxodboxop