Polybius square cipher • Cabinet Noir

Cabinet Noir>Encrypt / Polybius square cipher

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Every letter of the message becomes the row and column numbers of its cell in a 5×5 grid.

Typesubstitution cipher

Breaking ittrivial to break

EraClassical Greece, 2nd century BC

NamePolybius' torch-signalling scheme, later the basis of tap code and fractionation

Modesencrypt · decrypt

Message

Square key

1

2

3

4

5

1

A

B

C

D

E

2

F

G

H

I

K

3

L

M

N

O

P

4

Q

R

S

T

U

5

V

W

X

Y

Z

The square — the highlighted cell (with its row and column) is the latest letter of the output.

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Created by Denys Grybov in 2021

v.0.4.0 // released on 25.10.2026