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ADFGVX cipher is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Description

The ADFGVX cipher was a manually applied field cipher used by the German Army during World War I. It was broken in 1918 by the French cryptanalyst Georges Painvin.

The workings of the cipher are described in the Wikipedia article, linked to above, and so will not be repeated here.

Write routines, functions etc. in your language to:

1. Encrypt suitable plaintext and decrypt the resulting cipher text using the ADFGVX cipher algorithm given a Polybius square (see 2. below) and a suitable key. For this purpose suitable means text consisting solely of ASCII upper case letters or digits.

2. Create a 6 x 6 Polybius square using a random combination of the letters A to Z and the digits 0 to 9 and then display it.

3. Given the number of letters (between 7 and 12 say) to use, create a key by selecting a suitable word at random from unixdict.txt and then display it. The word selected should be such that none of its characters are repeated.

Use these routines to create a Polybius square and a 9 letter key.

These should then be used to encrypt the plaintext: ATTACKAT1200AM and decrypt the resulting cipher text. Display here the results of both operations.

Note

As it's unclear from the Wikipedia article how to handle a final row with fewer elements than the number of characters in the key, either of the methods mentioned in Columnar transposition may be used. In the case of the second method, it is also acceptable to fill any gaps after shuffling by moving elements to the left which makes decipherment harder.

## 11l

Translation of: Nim

F encrypt(plainText, polybius, key)
V s = ‘’
L(ch) plainText
L(r) 6
L(c) 6
I polybius[r][c] == ch

DefaultDict[Char, String] cols
L(ch) s
cols[key[L.index % key.len]] ‘’= ch

V result = ‘’
L(k) sorted(cols.keys())
I !result.empty
result ‘’= ‘ ’
result ‘’= cols[k]
R result

F decrypt(cipherText, polybius, key)
V skey = sorted(key)
V cols = [‘’] * key.len
V idx = 0
L(col) cipherText.split(‘ ’)
cols[key.findi(skey[idx])] = col
idx++

V s = ‘’
L(i) 0 .< key.len
L(col) cols
I i < col.len
s ‘’= col[i]

V result = ‘’
L(i) (0 .< s.len - 1).step(2)
V c = :adfgvx.findi(s[i + 1])
result ‘’= polybius[r][c]
R result

V polybius = [[Char("\0")] * 6] * 6
V alphabet = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789’
random:shuffle(&alphabet)
L(r) 6
L(c) 6
polybius[r][c] = alphabet[6 * r + c]

print("6 x 6 Polybius square:\n")
print(‘ | A D F G V X’)
print(‘---------------’)
L(row) polybius

V words = File(‘unixdict.txt’).read().split("\n").filter(w -> w.len == 9 & w.len == Set(Array(w)).len)
V key = random:choice(words).uppercase()
print("\nThe key is "key)

V PlainText = ‘ATTACKAT1200AM’
print("\nPlaintext : "PlainText)

V cipherText = encrypt(PlainText, polybius, key)
print("\nEncrypted : "cipherText)

V plainText = decrypt(cipherText, polybius, key)
print("\nDecrypted : "plainText)
Output:
6 x 6 Polybius square:

| A D F G V X
---------------
A | X O F P D 6
D | V H C 4 0 Z
F | J M K R U 5
G | I A 9 Y B W
V | 3 L 2 1 N G
X | Q T E 7 8 S

The key is EXCURSION

Plaintext : ATTACKAT1200AM

Encrypted : XFD GFVD GDG DGF DVD XDD DXV DGV DFF

Decrypted : ATTACKAT1200AM

## F#

// ADFGVX cipher. Nigel Galloway: August 23rd., 2021
let polybus=let n=[|yield! {'A'..'Z'}; yield! {'0'..'9'}|] in MathNet.Numerics.Combinatorics.GeneratePermutation 36|>Array.map(fun g->n.[g]),[|'A';'D';'F';'G';'V';'X'|]
let printPolybus(a,g)=printf " "; g|>Array.iter(printf "%c "); printfn ""; printfn " ----------------"
g|>Array.iteri(fun n g->printf " %c|" g; [0..5]|>List.iter(fun g->printf " %c " (Array.item(n*6+g) a)); printfn "")
let c2p n g=let g=(fst>>(Array.findIndex((=) g))) n in let (n:char[])=(snd n) in [|n.[g/n.Length];n.[g%n.Length]|]
let p2c n (g:char[])=Array.item(let n=snd n in (Array.findIndex((=)g.[0]) n)*n.Length+(Array.findIndex((=)g.[1]) n))(fst n)
let fN(g:string)=let e,d=let n=g|>Seq.sort|>List.ofSeq in (g|>Seq.mapi(fun i l->(List.findIndex((=)l)n)-i)|>Array.ofSeq,n|>Seq.mapi(fun i l->(Seq.findIndex((=)l)g)-i)|>Array.ofSeq)
(fun i->i+(e.[i%g.Length])),(fun i->i+(d.[i%g.Length]))
let ADFGVX n (g:string)=let pE,pD=fN g
(fun(s:string)->let a,b=s|>Seq.collect(c2p n)|>Array.ofSeq|>Array.splitAt(2*s.Length-(2*s.Length)%g.Length)
Array.append(Array.permute(pE) a)(Array.permute(fst(fN(g.[..b.Length-1]))) b)|>System.String),
(fun(s:string)->let a,b=s.ToCharArray()|>Array.splitAt(s.Length-(s.Length)%g.Length)
Array.append(Array.permute(pD) a)(Array.permute(snd(fN(g.[..b.Length-1]))) b)|>Array.chunkBySize 2|>Array.map(p2c n)|>System.String)

printPolybus polybus
let encrypt,decrypt=ADFGVX polybus "nigel" //Using "nigel" as the key no hacker will guess that!
let n=encrypt "ATTACKAT1200AM" in printfn \$"\nATTACKAT1200AM encrypted is %s{n} which decrypted is %s{decrypt n}"

Output:
A  D  F  G  V  X
----------------
A| 6  U  9  B  2  H
D| C  G  O  N  Y  R
F| T  8  D  E  V  K
G| 1  Q  X  P  L  W
V| Z  0  I  A  J  S
X| 7  4  3  M  F  5

ATTACKAT1200AM encrypted is AFGFVDGVAAGVXFFAAGVADVDVVGXG which decrypted is ATTACKAT1200AM

## Go

Translation of: Wren
package main

import (
"bytes"
"fmt"
"io/ioutil"
"log"
"math/rand"
"sort"
"strings"
"time"
)

var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

func distinct(bs []byte) []byte {
var u []byte
for _, b := range bs {
if !bytes.Contains(u, []byte{b}) {
u = append(u, b)
}
}
return u
}

func allAsciiAlphaNum(word []byte) bool {
for _, b := range word {
if !((b >= 48 && b <= 57) || (b >= 65 && b <= 90) || (b >= 97 && b <= 122)) {
return false
}
}
return true
}

func orderKey(key string) []int {
temp := make([][2]byte, len(key))
for i := 0; i < len(key); i++ {
temp[i] = [2]byte{key[i], byte(i)}
}
sort.Slice(temp, func(i, j int) bool { return temp[i][0] < temp[j][0] })
res := make([]int, len(key))
for i := 0; i < len(key); i++ {
res[i] = int(temp[i][1])
}
return res
}

func createPolybius() []string {
temp := []byte(alphabet)
rand.Shuffle(36, func(i, j int) {
temp[i], temp[j] = temp[j], temp[i]
})
alphabet = string(temp)
fmt.Println("6 x 6 Polybius square:\n")
fmt.Println(" | A D F G V X")
fmt.Println("---------------")
p := make([]string, 6)
for i := 0; i < 6; i++ {
p[i] = alphabet[6*i : 6*(i+1)]
for _, c := range p[i] {
fmt.Printf("%c ", c)
}
fmt.Println()
}
return p
}

func createKey(n int) string {
if n < 7 || n > 12 {
log.Fatal("Key should be within 7 and 12 letters long.")
}
if err != nil {
}
words := bytes.Split(bs, []byte{'\n'})
var candidates [][]byte
for _, word := range words {
if len(word) == n && len(distinct(word)) == n && allAsciiAlphaNum(word) {
candidates = append(candidates, word)
}
}
k := string(bytes.ToUpper(candidates[rand.Intn(len(candidates))]))
fmt.Println("\nThe key is", k)
return k
}

func encrypt(polybius []string, key, plainText string) string {
temp := ""
outer:
for _, ch := range []byte(plainText) {
for r := 0; r <= 5; r++ {
for c := 0; c <= 5; c++ {
if polybius[r][c] == ch {
continue outer
}
}
}
}
colLen := len(temp) / len(key)
// all columns need to be the same length
if len(temp)%len(key) > 0 {
colLen++
}
table := make([][]string, colLen)
for i := 0; i < colLen; i++ {
table[i] = make([]string, len(key))
}
for i := 0; i < len(temp); i++ {
table[i/len(key)][i%len(key)] = string(temp[i])
}
order := orderKey(key)
cols := make([][]string, len(key))
for i := 0; i < len(key); i++ {
cols[i] = make([]string, colLen)
for j := 0; j < colLen; j++ {
cols[i][j] = table[j][order[i]]
}
}
res := make([]string, len(cols))
for i := 0; i < len(cols); i++ {
res[i] = strings.Join(cols[i], "")
}
return strings.Join(res, " ")
}

func decrypt(polybius []string, key, cipherText string) string {
colStrs := strings.Split(cipherText, " ")
// ensure all columns are same length
maxColLen := 0
for _, s := range colStrs {
if len(s) > maxColLen {
maxColLen = len(s)
}
}
cols := make([][]string, len(colStrs))
for i, s := range colStrs {
var ls []string
for _, c := range s {
ls = append(ls, string(c))
}
if len(s) < maxColLen {
cols[i] = make([]string, maxColLen)
copy(cols[i], ls)
} else {
cols[i] = ls
}
}
table := make([][]string, maxColLen)
order := orderKey(key)
for i := 0; i < maxColLen; i++ {
table[i] = make([]string, len(key))
for j := 0; j < len(key); j++ {
table[i][order[j]] = cols[j][i]
}
}
temp := ""
for i := 0; i < len(table); i++ {
temp += strings.Join(table[i], "")
}
plainText := ""
for i := 0; i < len(temp); i += 2 {
plainText = plainText + string(polybius[r][c])
}
return plainText
}

func main() {
rand.Seed(time.Now().UnixNano())
plainText := "ATTACKAT1200AM"
polybius := createPolybius()
key := createKey(9)
fmt.Println("\nPlaintext :", plainText)
cipherText := encrypt(polybius, key, plainText)
fmt.Println("\nEncrypted :", cipherText)
plainText2 := decrypt(polybius, key, cipherText)
fmt.Println("\nDecrypted :", plainText2)
}
Output:

Sample run:

6 x 6 Polybius square:

| A D F G V X
---------------
A | R W H N I 7
D | 1 J O 2 P 5
F | 3 A T 4 M 9
G | D U L K V 0
V | Z B E F 6 Q
X | G Y S 8 C X

The key is EUCHARIST

Plaintext : ATTACKAT1200AM

Encrypted : FDG FGG FVDV FFX FFF FFX DDD XAF DGG

Decrypted : ATTACKAT1200AM

## Julia

"""
"""

using Random

""" The WWI German ADFGVX cipher. """
polybius::Vector{Char}
pdim::Int
key::Vector{Char}
keylen::Int
alphabet::Vector{Char}
encode::Dict{Char, Vector{Char}}
decode::Dict{Vector{Char}, Char}
end

""" ADFGVX constructor, takes 2 strings, option for third string if polybius len != 36 """
poly = collect(uppercase(s))
pdim = isqrt(length(poly))
al = collect(uppercase(alph))
enco::Dict = Dict([(poly[(i - 1) * pdim + j] => [al[i], al[j]])
for i in 1:pdim, j in 1:pdim])
deco = Dict(last(p) => first(p) for p in enco)
@assert pdim^2 == length(poly) && pdim == length(al)
return ADFGVX(poly, pdim, collect(uppercase(k)), length(k), al, enco, deco)
end

""" Encrypt with the ADFGVX cipher. """
chars = reduce(vcat, [k.encode[c] for c in
filter(c -> c in k.polybius, collect(uppercase(s)))])
colvecs = [lett => chars[i:k.keylen:length(chars)] for (i, lett) in enumerate(k.key)]
sort!(colvecs, lt = (x, y) -> first(x) < first(y))
return String(mapreduce(p -> last(p), vcat, colvecs))
end

""" Decrypt with the ADFGVX cipher. Does not depend on spacing of encoded text """
chars = filter(c -> c in k.alphabet, collect(uppercase(s)))
sortedkey = sort(collect(k.key))
order = [findfirst(c -> c == ch, k.key) for ch in sortedkey]
originalorder = [findfirst(c -> c == ch, sortedkey) for ch in k.key]
a, b = divrem(length(chars), k.keylen)
strides = [a + (b >= i ? 1 : 0) for i in order] # shuffled column lengths
starts = accumulate(+, strides[begin:end-1], init=1) # shuffled starts of columns
pushfirst!(starts, 1) # starting index
ends = [starts[i] + strides[i] - 1 for i in 1:k.keylen] # shuffled ends of columns
cols = [chars[starts[i]:ends[i]] for i in originalorder] # get reordered columns
pairs, nrows = Char[], (length(chars) - 1) ÷ k.keylen + 1 # recover the rows
for i in 1:nrows, j in 1:k.keylen
(i - 1) * k.keylen + j > length(chars) && break
push!(pairs, cols[j][i])
end
return String([k.decode[[pairs[i], pairs[i + 1]]] for i in 1:2:length(pairs)-1])
end

const POLYBIUS = String(shuffle(collect("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")))
const KEY = read("unixdict.txt", String) |>
v -> split(v, r"\s+") |>
v -> filter(w -> (n = length(w); n == 9 && n == length(unique(collect(w)))), v) |>
shuffle |> first |> uppercase
const SECRETS, message = ADFGVX(POLYBIUS, KEY), "ATTACKAT1200AM"
println("Polybius: \$POLYBIUS, Key: \$KEY")
println("Message: \$message")
encoded = encrypt(message, SECRETS)
decoded = decrypt(encoded, SECRETS)
println("Encoded: \$encoded")
println("Decoded: \$decoded")

Output:
Polybius: L4VZJIB8OXGFM1H3CTNKU9PE75WQ2DAYRS06, Key: SUNFLOWER
Message: ATTACKAT1200AM
Encoded: AFAXXVFAXFDXXFVFDFXVVAAGVXXX
Decoded: ATTACKAT1200AM

## Nim

Translation of: Wren

It started as a translation, but actually we use a different method, better suited to Nim, to encrypt and decrypt. And there are many other differences. Output is similar though.

import algorithm, random, sequtils, strutils, sugar, tables

type PolybiusSquare = array[6, array[6, char]]

iterator items(p: PolybiusSquare): (int, int, char) =
## Yield Polybius square characters preceded by row and column numbers.
for r in 0..5:
for c in 0..5:
yield (r, c, p[r][c])

proc initPolybiusSquare(): PolybiusSquare =
## Initialize a 6x6 Polybius square.
var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
alphabet.shuffle()
for r in 0..5:
for c in 0..5:
result[r][c] = alphabet[6 * r + c]

proc createKey(n: Positive): string =
## Create a key using a word from "unixdict.txt".
doAssert n in 7..12, "Key should be within 7 and 12 letters long."
let candidates = collect(newSeq):
for word in "unixdict.txt".lines:
if word.len == n and
word.deduplicate().len == n and
word.allCharsInSet(Letters + Digits): word
result = candidates[rand(candidates.high)].toUpperAscii

func encrypt(plainText: string; polybius: PolybiusSquare; key: string): string =
## Encrypt "plaintext" using the given Polybius square and the given key.

# Replace characters by row+column letters.
var str: string
for ch in plainText:
for (r, c, val) in polybius:
if val == ch:

# Build ordered table of columns and sort it by key value.
var cols: OrderedTable[char, string]
for i, ch in str:
let tkey = key[i mod key.len]
cols.sort(cmp)

# Build cipher text from sorted column table values.
for s in cols.values:

func decrypt(cipherText: string; polybius: PolybiusSquare; key: string): string =
## Decrypt "cipherText" using the given Polybius square and the given key.

# Build list of columns.
let skey = sorted(key)
var cols = newSeq[string](key.len)
var idx = 0
for col in cipherText.split(' '):
cols[key.find(skey[idx])] = col
inc idx

# Build string of row+column values.
var str: string
for i in 0..key.high:
for col in cols:
if i < col.len: str.add col[i]

# Build plain text from row+column values.
for i in countup(0, str.len - 2, 2):

randomize()

var polybius = initPolybiusSquare()
echo "6 x 6 Polybius square:\n"
echo " | A D F G V X"
echo "---------------"
for i, row in polybius:
echo Adfgvx[i], " | ", row.join(" ")

let key = createKey(9)
echo "\nThe key is ", key

const PlainText = "ATTACKAT1200AM"
echo "\nPlaintext : ", PlainText

let cipherText = PlainText.encrypt(polybius, key)
echo "\nEncrypted : ", cipherText

let plainText = cipherText.decrypt(polybius, key)
echo "\nDecrypted : ", plainText
Output:
6 x 6 Polybius square:

| A D F G V X
---------------
A | U 1 C N H F
D | E M 4 R S G
F | P I 8 9 6 5
G | X 2 Z B 7 K
V | A 3 Y V O D
X | 0 W Q T J L

The key is PHAGOCYTE

Plaintext : ATTACKAT1200AM

Encrypted : XXX GXA ADD GVA AGD XAX VFGD AAA VGV

Decrypted : ATTACKAT1200AM

## Perl

#!/usr/bin/perl

use warnings;
use List::Util qw( shuffle );

my \$plaintext = 'ATTACKAT1200AM';
my \$keysize = 9;

my \$polybius = <<END;
| A D F G V X
--+------------
A | x x x x x x
D | x x x x x x
F | x x x x x x
G | x x x x x x
V | x x x x x x
X | x x x x x x
END

\$polybius =~ s/x/\$_/ for my @letters = shuffle "A" .. 'Z' , 0 .. 9;
print "Polybius square =\n\n\$polybius\n";
my %char2pair;
@char2pair{ @letters } = glob '{A,D,F,G,V,X}' x 2; # map chars to pairs
my %pair2char = reverse %char2pair; # map pairs to chars
my (\$keyword) = shuffle grep !/(.).*\1/,
do { local (@ARGV, \$/) = 'unixdict.txt'; <> =~ /^.{\$keysize}\$/gm };
my (\$n, @deorder) = 0;
my @reorder = map /.(.+)/, sort map \$_ . \$n++, split //, \$keyword;
@deorder[@reorder] = 0 .. \$#reorder;
print " keyword = \$keyword\n\nplaintext = \$plaintext\n\n";

my \$encoded = encode( \$plaintext, \%char2pair, \@reorder );
print " encoded = \$encoded\n\n";

my \$decoded = decode( \$encoded, \%pair2char, \@deorder );
print " decoded = \$decoded\n";

sub encode
{
my (\$plain, \$c2p, \$order) = @_;
my \$len = @\$order;
join ' ', (transpose( \$plain =~ s/./\$c2p->{\$&}/gr =~ /.{1,\$len}/g ))[@\$order];
}

sub decode
{
my (\$encoded, \$p2c, \$order) = @_;
(join '', transpose((split ' ', \$encoded)[@\$order])) =~ s/../\$p2c->{\$&}/gr;
}

sub transpose { map join('', map {s/.// ? \$& : ''} @_), 1 .. length \$_[0] }
Output:
Polybius square =

| A D F G V X
--+------------
A | 6 V Y E P N
D | 1 C M 9 L H
F | 8 T O U D F
G | A R G 7 S 5
V | J 2 W Q I Z
X | K B 3 0 X 4

keyword = benchmark

plaintext = ATTACKAT1200AM

decoded = ATTACKAT1200AM

## Phix

Translation of: Wren
We can make some nice use of the standard builtin routines here, with only a modest amount of whitespace cleanup.
with javascript_semantics
ALEPH = tagset('Z','A')&tagset('9','0')

function create_polybius()
string aleph = shuffle(ALEPH)
--  string aleph = "U1CNHFEM4RSGPI8965X2ZB7KA3YVOD0WQTJL"   -- Nim
--  string aleph = "T71VB5HYG2JKIQM8REOPDUNCZ063FXAW9S4L"   -- Wren
--  string aleph = "NA1C3H8TB2OME5WRPD4F6G7I9J0KLQSUVXYZ"   -- wp
sequence tmp = split(join_by(aleph,1,6," "),'\n')
printf(1,"6 x 6 Polybius square:\n")
printf(1,"  | A D F G V X\n")
printf(1,"---------------\n")
for i=1 to length(tmp) do
end for
return aleph
end function

function lnua(string word, integer n)
return length(word)==n
and length(unique(word))==n
and length(filter(word,"in",ALEPH))==n
end function

function create_key(integer n)
assert(n>=7 and n<=12)
sequence candidates = filter(upper(unix_dict()),lnua,n)
string res = candidates[rand(length(candidates))]
--  string res = "PHAGOCYTE" -- Nim
--  string res = "SUNFLOWER" -- Wren
--  string res = "PRIVACY" -- wp
printf(1,"\nThe key is %s\n",{res})
return res
end function

function encrypt(string polybius, key, plaintext)
integer l = length(key)
sequence tags = custom_sort(key,tagset(l)),
res = ""
for i=1 to length(plaintext) do
integer k = find(plaintext[i],polybius)
if k then   -- (simply ignore any non-alphanum)
end if
end for
res = substitute(join(columnize(split_by(res,l),tags,' ')),"  "," ")
return res
end function

function decrypt(string polybius, key, encrypted)
integer l = length(key)
sequence tags = custom_sort(key,tagset(l)),
tmp = columnize(split(encrypted,' '),{},' ')
tmp = trim(join(apply(true,extract,{tmp,{tags},true}),""))
string plaintext = ""
for i=1 to length(tmp) by 2 do
plaintext &= polybius[r*6+c]
end for
return plaintext
end function

string polybius = create_polybius(),
key = create_key(9),
plaintext = "ATTACKAT1200AM",
encrypted = encrypt(polybius,key,plaintext),
decrypted = decrypt(polybius,key,encrypted)
printf(1,"\nPlainText : %s\n\nEncrypted : %s\n\nDecrypted : %s\n",
{plaintext,        encrypted,        decrypted})

Output matches Wren/Nim/wp when the appropriate lines are uncommented.

## Python

This version and the Julia version do not reveal the key length by preserving spaces between columns, which completely removes column information, not just hiding which columns are first in the encoding. According to historical sources the original encrypted text was spaced in 5 character blocks regardless of message and key length, which means that decryption should not rely on spacing.

"""
The ADFGVX cipher implemented as a Python class
"""

from random import shuffle, choice
from itertools import product, accumulate
from numpy import floor, sqrt

""" The WWI German ADFGVX cipher. """
self.polybius = list(spoly.upper())
self.pdim = int(floor(sqrt(len(self.polybius))))
self.key = list(k.upper())
self.keylen = len(self.key)
self.alphabet = list(alph)
pairs = [p[0] + p[1] for p in product(self.alphabet, self.alphabet)]
self.encode = dict(zip(self.polybius, pairs))
self.decode = dict((v, k) for (k, v) in self.encode.items())

def encrypt(self, msg):
""" Encrypt with the ADFGVX cipher. """
chars = list(''.join([self.encode[c] for c in msg.upper() if c in self.polybius]))
colvecs = [(lett, chars[i:len(chars):self.keylen]) \
for (i, lett) in enumerate(self.key)]
colvecs.sort(key=lambda x: x[0])
return ''.join([''.join(a[1]) for a in colvecs])

def decrypt(self, cod):
""" Decrypt with the ADFGVX cipher. Does not depend on spacing of encoded text """
chars = [c for c in cod if c in self.alphabet]
sortedkey = sorted(self.key)
order = [self.key.index(ch) for ch in sortedkey]
originalorder = [sortedkey.index(ch) for ch in self.key]
base, extra = divmod(len(chars), self.keylen)
strides = [base + (1 if extra > i else 0) for i in order] # shuffled column lengths
starts = list(accumulate(strides[:-1], lambda x, y: x + y)) # shuffled starts of columns
starts = [0] + starts # starting index
ends = [starts[i] + strides[i] for i in range(self.keylen)] # shuffled ends of columns
cols = [chars[starts[i]:ends[i]] for i in originalorder] # get reordered columns
pairs = [] # recover the rows
for i in range((len(chars) - 1) // self.keylen + 1):
for j in range(self.keylen):
if i * self.keylen + j < len(chars):
pairs.append(cols[j][i])

return ''.join([self.decode[pairs[i] + pairs[i + 1]] for i in range(0, len(pairs), 2)])

if __name__ == '__main__':
PCHARS = list('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789')
shuffle(PCHARS)
POLYBIUS = ''.join(PCHARS)
with open('unixdict.txt') as fh:
WORDS = [w for w in (fh.read()).split() \
if len(w) == 9 and len(w) == len(set(list(w)))]
KEY = choice(WORDS)

SECRET, MESSAGE = ADFGVX(POLYBIUS, KEY), 'ATTACKAT1200AM'
print(f'Polybius: {POLYBIUS}, key: {KEY})
print('
Message: ', MESSAGE)
ENCODED = SECRET.encrypt(MESSAGE)
DECODED = SECRET.decrypt(ENCODED)
print('
Encoded: ', ENCODED)
print('
Decoded: ', DECODED)
Output:
Polybius: A9GKMF1DQRSBVX8Z0WTEJLOPY5U4CN2H76I3, key: volcanism
Message:  ATTACKAT1200AM
Decoded:  ATTACKAT1200AM

## Raku

Slightly different results from every other entry so far. See discussion page for reasons. It is impossible to tell from casual observation which column comes first in the Raku example. In every other (so far), the sub group with 4 characters is the first column.

srand 123456; # For repeatability

my @header = < A D F G V X >;
my \$polybius = (flat 'A'..'Z', 0..9).pick(*).join;

my \$key-length = 9;
my \$key = uc 'unixdict.txt'.IO.words.grep( { (.chars == \$key-length) && (+.comb.Set == +.comb) } ).roll;

my \$message = 'Attack at 1200AM';

use Terminal::Boxer;
say "Key: \$key\n";
say "Polybius square:\n", ss-box :7col, :3cw, :indent("\t"), '', |@header, |(@header Z \$polybius.comb.batch: 6);
say "Message to encode: \$message";
say "\nEncoded: " ~ my \$encoded = encode \$message;
say "\nDecoded: " ~ decode \$encoded;

sub encode (\$text is copy) {
\$text = \$text.uc.comb(/<[A..Z 0..9]>/).join;
my @order = \$key.comb.pairs.sort( *.value )».key;
my @encode = %cypher.invert.hash{ \$text.comb }.join.comb.batch(\$key-length).map: { [\$_] };
((^\$key-length).map: { @encode».[@order]».grep( *.defined )».[\$_].grep( *.defined ).join }).Str;
}

sub decode (\$text is copy) {
my @text = \$text.split(' ')».comb;
my \$chars = @text[0].chars;
\$_ = flat |\$_, ' ' if .chars < \$chars for @text;
my @order = \$key.comb.pairs.sort( *.value )».key.pairs.sort( *.value )».key;
%cypher{ ( grep { /\w/ }, flat [Z] @order.map( { |@text.batch(\$key-length)».[\$_] } ) ).batch(2)».join }.join;
}
Output:
Key: GHOSTLIKE

Polybius square:
┌───┬───┬───┬───┬───┬───┬───┐
│   │ A │ D │ F │ G │ V │ X │
├───┼───┼───┼───┼───┼───┼───┤
│ A │ H │ O │ S │ 5 │ 7 │ Q │
├───┼───┼───┼───┼───┼───┼───┤
│ D │ 0 │ I │ 6 │ J │ C │ V │
├───┼───┼───┼───┼───┼───┼───┤
│ F │ 4 │ 8 │ R │ X │ G │ A │
├───┼───┼───┼───┼───┼───┼───┤
│ G │ Y │ F │ P │ B │ Z │ 3 │
├───┼───┼───┼───┼───┼───┼───┤
│ V │ M │ W │ 9 │ D │ 1 │ N │
├───┼───┼───┼───┼───┼───┼───┤
│ X │ 2 │ E │ U │ T │ L │ K │
└───┴───┴───┴───┴───┴───┴───┘

Message to encode: Attack at 1200AM

Encoded: DVVA FVX XXA FGF XVX GXA XXD GFA XXD

Decoded: ATTACKAT1200AM

## Wren

Library: Wren-ioutil
Library: Wren-seq
Library: Wren-str
import "random" for Random
import "/ioutil" for FileUtil
import "/seq" for Lst
import "/str" for Char, Str

var rand = Random.new()
var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toList

var createPolybius = Fn.new {
rand.shuffle(alphabet)
var p = Lst.chunks(alphabet, 6)
System.print("6 x 6 Polybius square:\n")
System.print(" | A D F G V X")
System.print("---------------")
for (i in 0...p.count) {
System.print(p[i].join(" "))
}
return p
}

var createKey = Fn.new { |n|
if (n < 7 || n > 12) Fiber.abort("Key should be within 7 and 12 letters long.")
var candidates = FileUtil.readLines("unixdict.txt").where { |word|
return word.count == n && Lst.distinct(word.toList).count == n &&
word.all { |ch| Char.isAsciiAlphaNum(ch) }
}.toList
var k = Str.upper(candidates[rand.int(candidates.count)])
System.print("\nThe key is %(k)")
return k
}

// helper function to sort the key into alphabetical order
// and return a list of the original indices of its letters.
var orderKey = Fn.new { |key|
var temp = (0...key.count).map { |i| [key[i], i] }.toList
temp.sort { |x, y| x[0].bytes[0] < y[0].bytes[0] }
return temp.map { |e| e[1] }.toList
}

var encrypt = Fn.new { |polybius, key, plainText|
var temp = ""
for (ch in plainText) {
var outer = false
for (r in 0..5) {
for (c in 0..5) {
if (polybius[r][c] == ch) {
outer = true
break
}
}
if (outer) break
}
}
var colLen = (temp.count / key.count).floor
// all columns need to be the same length
if (temp.count % key.count > 0) colLen = colLen + 1
var table = Lst.chunks(temp.toList, key.count)
var lastLen = table[-1].count
if (lastLen < key.count) table[-1] = table[-1] + ([""] * (key.count - lastLen))
var order = orderKey.call(key)
var cols = List.filled(key.count, null)
for (i in 0...cols.count) {
cols[i] = List.filled(colLen, null)
for (j in 0...table.count) cols[i][j] = table[j][order[i]]
}
return cols.map { |col| col.join() }.join(" ")
}

var decrypt = Fn.new { |polybius, key, cipherText|
var colStrs = cipherText.split(" ")
// ensure all columns are same length
var maxColLen = colStrs.reduce(0) { |max, col| max = (col.count > max) ? col.count : max }
var cols = colStrs.map { |s|
return (s.count < maxColLen) ? s.toList + ([""] * (maxColLen - s.count)) : s.toList
}.toList
var table = List.filled(maxColLen, null)
var order = orderKey.call(key)
for (i in 0...maxColLen) {
table[i] = List.filled(key.count, "")
for (j in 0...key.count) table[i][order[j]] = cols[j][i]
}
var temp = table.map { |row| row.join("") }.join("")
var plainText = ""
var i = 0
while (i < temp.count) {
plainText = plainText + polybius[r][c]
i = i + 2
}
return plainText
}

var plainText = "ATTACKAT1200AM"
var polybius = createPolybius.call()
var key = createKey.call(9)
System.print("\nPlaintext : %(plainText)")
var cipherText = encrypt.call(polybius, key, plainText)
System.print("\nEncrypted : %(cipherText)")
var plainText2 = decrypt.call(polybius, key, cipherText)
System.print("\nDecrypted : %(plainText2)")
Output:

Sample run:

6 x 6 Polybius square:

| A D F G V X
---------------
A | T 7 1 V B 5
D | H Y G 2 J K
F | I Q M 8 R E
G | O P D U N C
V | Z 0 6 3 F X
X | A W 9 S 4 L

The key is SUNFLOWER

Plaintext : ATTACKAT1200AM