GRGR 5: Hey, Wait Up for Me!

[Alan Westrope]

On Fri, 22 Nov 1996, LARSSON at VAX1.Mankato.MSUS.EDU wrote:

>Does anyone understand the reference to "a simple Nihilist transposition"?
>Sounds like some kind of term for a system of encryption, but is it?

Yes, and it's a simple one that Pirate could perhaps do in his head.
Transposition ciphers use the same characters as the plaintext message,
but scu^Hramble them into a new sequence, usually by transposing rows and
columns -- a simple transposition cipher of this paragraph might begin:

YTbc eruo satl

(I'm simplifying due to time constraints, but you get the idea.)  A
Nihilist has the same number of rows and columns, which often requires
padding the message with some nonsense, or 'null', characters.  An
example I have at hand from Gerhard Linz' _NOVICE NOTES_ uses the text
THE EARLY BIRD GETS THE WORM.  (Appropriately ornithological, given our
recent Parker forays...)  It has 23 letters, so we'll append an X and a
Y to make a 5x5 matrix, requiring a 5-letter keyword, like THINK.  In
the alphabet, the first letter of THINK that occurs is H, followed by I,
K, N, and T, so the word corresponds to the numbers 51243.  We prepare
the message thusly:

   THINK
   51243
   -----
T5|theea
H1|rlybi
I2|rdget
N4|sthew
K3|ormxy

and arrange rows and columns by numbers:

   HIKNT
   12345
   -----
H1|lyibr
I2|dgter
K3|rmyxo
N4|thwes
T5|heaet

The ciphertext is usually taken out by columns, giving

ldrth ygmhe itywa bexee rrost

That's the general idea, anyway, and I hope I haven't screwed up
too much.  No time now to explain decryption...I'm overwhelmed
with (among other things) reading the responses to section 5, which
is perhaps my favorite vignette in GR.  (I mean Slothrop's Toilet
and Bebop Hallucination, *not* Pirate jerking off, dammit!!! :-)


-- 
Alan Westrope     PGP public key:  http://www.crl.com/~awestrop
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<awestrop at nyx.net>
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