cipher.codes
Polybius Square
About
Polybius Square a cipher where each alphanumeric (a-z, 0-9) character is represented by it’s coordinates in a grid.
Supports
❌ Perfect Decoding
✅ Uppercase letters (A-Z)
✅ Lowercase letters (a-z)
✅ Numbers (0-9)
❌ Symbols (!@#$)
❌ Emojis (😍🤬👩🏾💻)
Numbers and Emojis
Symbols and emoji are removed by this cipher.
Spaces are Removed
All spaces are removed by this cipher during encoding.
What is “Perfect Decoding”?
Perfect Decoding is when the decoded text exactly matches the text that was encoded.
This cipher forcibly lowercases all characters, removes spaces, omits symbols and emoji. As a result the output from decoding does not exactly match the original input string.
Source
View Polybius Square on Github
Formula
Encoding
x = Math.floor(letterPosition / 6) + 1
y = (letterPosition mod 6) + 1
Decoding
characterIndex = (x * 6) + y
Live Example
Sample String
Hello World!
ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz
0123456789
!@#$
✨🦄✨
When, Encoded
22 15 26 26 33 45 33 36 26 14 11 12 13 14 15 16 21 22 23 24 25 26 31 32 33 34 35 36 41 42 43 44 45 46 51 52 11 12 13 14 15 16 21 22 23 24 25 26 31 32 33 34 35 36 41 42 43 44 45 46 51 52 53 54 55 56 61 62 63 64 65 66
Then, Decoded
helloworldabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789
How it works
letterPositionis the index of the letterxandyare the coordinates of the letter in a 6x6alphanumeric gridcharacterIndexis the index of the character in a flatalphanumeric array
Alphanumeric Grid and Array
The alphanumeric array consists of the letters a-z and 0-9.
Alphanumeric Array:
abcdefghijklmnopqrstuvwxyz0123456789
Alphanumeric Grid:
a b c d e f
g h i j k l
m n o p q r
s t u v w x
y z 0 1 2 3
4 5 6 7 8 9
“Magic” Number 6
The 6 represents the number of rows and columns in the alphanumeric grid.
letterPosition
Index of the letter in the alphanumeric alphabet (0-indexed). For example, A=0, C=2, Z=25, and 9=35.
x and y
Given the grid above, where:
a = 1,1m = 3,1w = 4,59 = 6,6
We can use the formula for encoding to calculate thexandyvalues for a given character in the grid.
characterIndex
Given a set of character coordinates (1,1 through 6,6), calculate the 0-index of the letter at that coordinate. This characterIndex is then used to lookup the letter in the alphanumeric array.
A note on mod
The formula for encoding uses mod 6. Javascript doesn’t have proper support for mod so this formula is used:
export function mod (a, b) {
return ((a % b) + b) % b
}
