Editing Polybius square (section)

==Basic form==
According to Polybius' ''Histories,'' the device was invented by [[Cleoxenus]] and [[Democleitus]], and further developed by Polybius himself. The device partitioned the alphabet into five tablets with five letters each (except for the last one with only four). There are no surviving tablets from antiquity. Letters are represented by two numbers from one to five, allowing the representation of 25 characters using only 5 numeric symbols.

The original square used the [[Greek alphabet]] laid out as follows:
{| class="wikitable"
!
! 1 !! 2 !! 3 !! 4 !! 5
|-
! 1
| [[Α]] || [[Β]] || [[Γ]] || [[Δ]] || [[Ε]]
|-
! 2
| [[Ζ]] || [[Η]] || [[Θ]] || [[Ι]] || [[Κ]]
|-
! 3
| [[Λ]] || [[Μ]] || [[Ν]] || [[Ξ]] || [[Ο]]
|-
! 4
| [[Pi (letter)|Π]] || [[Ρ]] || [[Σ]] || [[Τ]] || [[Υ]]
|-
! 5
| [[Φ]] || [[Χ]] || [[Ψ]] || [[Ω]] || 
|}

Modern Greek still uses that same alphabet, as do implementations of the Polybius square in that language. 

With the [[Latin alphabet]], this is the typical form:

{| class="wikitable"
|-
! 
! 1 !! 2 !! 3 !! 4 !! 5
|-
! 1
| [[A]] || [[B]] || [[C]] || [[D]] || [[E]]
|-
! 2
| [[F]] || [[G]] || [[H]] || [[I]]/[[J]] ||[[K]]
|-
! 3
| [[L]] || [[M]] || [[N]] || [[O]] || [[P]]
|-
! 4
| [[Q]] || [[R]] || [[S]] || [[T]] || [[U]]
|-
! 5
| [[V]] || [[W]] || [[X]] || [[Y]] || [[Z]]
|}

This alphabet, and this latter form of the Polybius square, is used when implementing the square in other Western European languages such as English, Spanish, French, German, Italian, Portuguese, and Dutch. 

Each letter is then represented by its coordinates in the grid. For example, "BAT" becomes "12 11 44". The 26 letters of the Latin/English alphabet do not fit in a 5 × 5 square, two letters must be combined (usually I and J as above, though C and K is an alternative). Alternatively, a 6 × 6 grid may be used to allow numerals or special characters to be included as well as letters.

A 6 × 6 grid is also usually used for the [[Cyrillic alphabet]] (the most common variant has 33 letters, but some have up to 37) {{citation needed|date=January 2023}} or Japanese [[hiragana]] (see [[cryptography in Japan]]).

A [[Key (cryptography)|key]] could be used to reorder the alphabet in the square, with the letters (without duplicates) of the key being placed at the beginning and the remaining letters following it in alphabetical order.<ref name=":0">{{Cite book|last=Salomon, D. (David), 1938-|title=Data privacy and security : encryption and information hiding|date=2011|publisher=Springer|isbn=978-1-4419-1816-1|oclc=752480143}}</ref> For example, the key phrase "''polybius cipher"'' would lead to the reordered square below.
{| class="wikitable"
!
!'''1'''
!'''2'''
!'''3'''
!'''4'''
!'''5'''
|-
!'''1'''
|P
|O
|L
|Y
|B
|-
!'''2'''
|I/J
|U
|S
|C
|H
|-
!'''3'''
|E
|R
|A
|D
|F
|-
!'''4'''
|G
|K
|M
|N
|Q
|-
!'''5'''
|T
|V
|W
|X
|Z
|}