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254 |
Book
Five |
Ch.
14. |
Chapter XIV
On Oblique
Transposition in accordance with
An Alphabetic Arrangement of Letters
The
third Mode, or process, consists in a fortuitous collection of letters, selected with reference
to Transposition and arranged in a table. This
fortuitous combination, that is , depends on the arrangement of a single
alphabet, which is included in a table and the small spaces thereof; outside of
which table Valid letters, three of four in number, are twice written, in such
form as to resemble a carpenter’s square or measure, once above, and once at
the side, either at the right hand or the left; the aim being that we should be
able to transpose, in fit and lawful way, the letters of the secret sentence
into these three or four or at most five exterior letters, joined together. Cardano,
Bk. 12.c.61, and Porta, Bk. 2.c.12, as
well as others, among whom is also our friend de Vigenere, have
constructed tables of this kind, which I will elucidate by first explaining the
tables themselves and the principle of their construction, and then setting
forth their use.
|
|
AA |
BB |
CC |
AB |
AC |
BC |
CB |
This first table is found in de Vigenere, p 201. Porta, in the aforementioned Bk. 2.c.12, changes somewhat, in the matter of the exterior letters, both this table and |
|
A |
a |
d |
g |
l |
o |
x |
U |
|
|
B |
b |
e |
h |
m |
p |
s |
R |
|
|
C |
c |
f |
i |
n |
q |
t |
Z |
the following tables. He places, namely, three or four lateral letters at the right hand side. But there is not much difference in the two Modes, except that, in Porta’s Mode, we construct the writing by descending form the upper to the lateral letters, while, in the Mode here presented, we ascend from the letters below to those above.
|
|
F 1 5 |
G 2 6 |
Q 3 7 |
X 4 8 |
The second table, taken form de Vigenere, p. 243b, has this peculiarity, that, just as in the former cases we write with three letter, we hare write with four, while the interior table is composed of sixteen letters only. It results from this latter fact, that, from these eight letter, F.G.K.Q.T.X.Y.Z. we may select four and place them outside as capitals. This further fact should, however, be noted, that the interior alphabet may be so arranged that the letters follow one another by quaternions in squares that run in horizontal lines. |
|
F 1 5 |
a |
c |
m |
r |
|
|
G 2 6 |
b |
h |
n |
s |
|
|
Q 3 7 |
c |
i |
o |
t |
|
|
X 4 8 |
d |
l |
p |
u |
* * * *
In the third table, likewise taken from de Vigenere, p.202a, we write with five letters, but we may also in this case, keeping the same arrangement, write with four letters; as, for instance, if we substitute, in the horizontal line, DD for the capital letter E. There is here also this slight point