Polybius Square Cipher

Artificial Apps & Games

About this app

Polybius Square Cipher is a compact learning app for the classical 5x5 Polybius square.

Encode text into row-and-column coordinates, decode coordinates back into letters, and practise with short training challenges. I and J share position 24, and decoding 24 returns I.

Features:
- Encrypt and decrypt with live results
- Built-in letter and coordinate keyboards
- 5x5 square reference
- Training modes: Identify Coordinates, Decode Words and a 60-second Speed Round
- XP, accuracy and streak saved on your device
- Light and dark themes
- Works offline, no account needed

Important: Polybius is a historical teaching cipher. It does not provide modern encryption or confidentiality, and should not be used for passwords, financial details or sensitive messages.

What’s new

Initial release. Learn, encrypt, decrypt and practice the classic Polybius cipher offline, targeting Android 16 (API 36).