Free Online Tool

Hill Cipher

Encrypt text using matrix multiplication with the polygraphic Hill cipher system.

Hill Cipher

Matrix-based cipher

Mode

Input Text

Characters: 0Words: 0

Output Text

Example Texts

Click any example to load it

Hello World

Basic example

The quick brown fox jumps over the lazy dog

Pangram

Testing 123!

Mixed content

How to Use Hill Cipher

Enter plaintext and select Encode.
The current component strips nonletters, uppercases the input, and pads an odd length with X.
It multiplies each letter pair by the fixed matrix [[3,2],[5,7]] modulo 26.
Choose Decode to apply the matrix inverse and recover the padded plaintext.

A Hill cipher treats letter pairs as vectors. The default matrix has determinant 11, which is invertible modulo 26, so decryption is defined.

Fixed 2×2 matrix — input:

HELP

Output:

DLLE

Odd length receives X padding — input:

HELLO

Output:

DLDCKX

All processing happens in your browser. No data is sent to servers.

No registration, no limits, completely free to use.