The Alphabet Cipher Guide, Meaning , Facts, Information and Description
Lewis Carroll published The Alphabet-Cipher in 1868, possibly in a children's magazine. It describes what is known as a Vigenère cipher, a well-known scheme in cryptography. It is amusing to note that while Carroll calls this cipher "unbreakable", Kasiski had published a volume describing how to break such ciphers just five years earlier (see Vigenère cipher for a description of the method).Since this piece is short, interesting and in the public domain, it is included here in its entirety. Notice how it begins with a tabula recta.
EACH column of this table forms a dictionary of symbols representing the
alphabet: thus, in the A column, the symbol is the same as the letter
represented; in the B column, A is represented by B, B by C, and so on.
To use the table, some word or sentence should be agreed on by two
correspondents. This may be called the `key-word', or `key-sentence',
and should be carried in the memory only.
In sending a message, write the key-word over it, letter for letter,
repeating it as often as may be necessary: the letters of the key-word
will indicate which column is to be used in translating each letter of
the message, the symbols for which should be written underneath: then
copy out the symbols only, and destroy the first paper. It will now be
impossible for any one, ignorant of the key-word, to decipher the message,
even with the help of the table.
For example, let the key-word be vigilance, and the message `meet me on
Tuesday evening at seven', the first paper will read as follows --
The receiver of the message can, by the same process, retranslate it
into English.
N.B. — If this table be lost, it can easily be written out from memory,
by observing that the first symbol in each column is the same as the
letter naming the column, and that they are continued downwards in
alphabetical order. Of course it would only be necessary to write out the
particular columns required by the key-word: such a paper, however, should
not be preserved, as it would afford means for discovering the key-word. This is an Article on The Alphabet Cipher. Page Contains Information, Facts Details or Explanation Guide About The Alphabet Cipher The Alphabet-Cipher, Lewis Carroll, 1868
ABCDEFGHIJKLMNOPQRSTUVWXYZ
A abcdefghijklmnopqrstuvwxyz A
B bcdefghijklmnopqrstuvwxyza B
C cdefghijklmnopqrstuvwxyzab C
D defghijklmnopqrstuvwxyzabc D
E efghijklmnopqrstuvwxyzabcd E
F fghijklmnopqrstuvwxyzabcde F
G ghijklmnopqrstuvwxyzabcdef G
H hijklmnopqrstuvwxyzabcdefg H
I ijklmnopqrstuvwxyzabcdefgh I
J jklmnopqrstuvwxyzabcdefghi J
K klmnopqrstuvwxyzabcdefghij K
L lmnopqrstuvwxyzabcdefghijk L
M mnopqrstuvwxyzabcdefghijkl M
N nopqrstuvwxyzabcdefghijklm N
O opqrstuvwxyzabcdefghijklmn O
P pqrstuvwxyzabcdefghijklmno P
Q qrstuvwxyzabcdefghijklmnop Q
R rstuvwxyzabcdefghijklmnopq R
S stuvwxyzabcdefghijklmnopqr S
T tuvwxyzabcdefghijklmnopqrs T
U uvwxyzabcdefghijklmnopqrst U
V vwxyzabcdefghijklmnopqrstu V
W wxyzabcdefghijklmnopqrstuv W
X xyzabcdefghijklmnopqrstuvw X
Y yzabcdefghijklmnopqrstuvwx Y
Z zabcdefghijklmnopqrstuvwxy Z
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Explanation
v i g i l a n c e v i g i l a n c e v i g i l a n c e v i
m e e t m e o n t u e s d a y e v e n i n g a t s e v e n
h m k b x e b p x p m y l l y r x i i q t o l t f g z z v
The second will contain only 'h m k b x e b p x p m y l l y r x i i q t o l t f g z z v'.