Editing ADFGVX cipher (section)

== Operation ==
For the [[plaintext]] message, "Attack at once", a secret [[substitution cipher|mixed alphabet]] is first filled into a 5 × 5 [[Polybius square]]:
{| class="wikitable" style="text-align:center;"
!
!A
!D
!F
!G
!X
|-
!A
|b
|t
|a
|l
|p
|-
!D
|d
|h
|o
|z
|k
|-
!F
|q
|f
|v
|s
|n
|-
!G
|g
|i/j
|c
|u
|x
|-
!X
|m
|r
|e
|w
|y
|}
{{code|i}} and {{code|j}} have been combined to make the alphabet fit into a 5 × 5 grid.

By using the square, the message is converted to fractionated form:
:{| class="wikitable" style="text-align:center;"
| a || t || t || a || c || k || a || t || o || n || c || e
|-
| AF|| AD|| AD|| AF|| GF|| DX|| AF|| AD|| DF|| FX|| GF|| XF
|}

The first letter of each ciphertext pair is the row, and the second ciphertext letter is the column, of the plaintext letter in the grid (''e.g.'', "AF" means "row A, column F, in the grid").

Next, the fractionated message is subject to a [[Transposition cipher#Columnar transposition|columnar transposition]]. The message is written in rows under a transposition key (here "CARGO"):

 '''C A R G O'''
 _________
 A F A D A
 D A F G F
 D X A F A
 D D F F X
 G F X F

Next, the letters are sorted alphabetically in the transposition key (changing CARGO to ACGOR) by rearranging the columns beneath the letters along with the letters themselves:

 '''A C G O R'''
 _________
 F A D A A
 A D G F F
 X D F A A
 D D F X F
 F G F   X

Then, it is read off in columns, in keyword order, which yields the [[ciphertext]]:
 FAXDF ADDDG DGFFF AFAX AFAFX
In practice, the transposition keys were about two dozen characters long. Long messages sent in the ADFGX cipher were broken into sets of messages of different and irregular lengths to make it invulnerable to multiple anagramming.<ref name="WWI_Codebreaking"/> Both the transposition keys and the fractionation keys were changed daily.