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Trifid Cipher

Trifid Cipher

Encrypt and decrypt text with the Trifid cipher — a classical fractionating cipher by Félix Delastelle that uses a keyed 3×3×3 Polybius cube to split letters into layer, row, and column coordinates.

Input
0 chars · 0 bytes
Try:
Result
✓ Based on a 3×3×3 Polybius cube with keyword ✓ Fractionation: coordinates split across three layers ✓ We never store your messages ✓ Processed on our server
Examples
Encrypt with Trifid Key: KEYWORD
Input HELLO
Output FFOF1

Basic Trifid encryption example using English alphabet (J→I, two numeric pads).

Decrypt with Trifid Key: KEYWORD
Input FFOF1
Output HELLO

Decryption using the same keyword and English alphabet.

Encrypt a phrase with Trifid Key: KEYWORD
Input MEET ME AT NOON
Output CUAEQDTLOSNI

English Trifid example showing that spaces are ignored before the keyed 3×3×3 cube calculation.

Longer Trifid encryption example Key: PLAYFAIR
Input ATTACKATDAWN
Output CLBBPBPIW1VV

A longer English Trifid example showing how coordinate fractionation diffuses repeated letters across the ciphertext.

How the Trifid Cipher works

The Trifid Cipher is a classical fractionating cipher invented by Félix Delastelle, the same cryptographer who created the Bifid cipher. Instead of a 2D Polybius square, Trifid uses a 3×3×3 Polybius cube: each cell contains one alphabet symbol, and each plaintext letter is represented by three coordinates — layer, row, and column.

During encryption, the service builds the cube from your keyword, writes all layer coordinates first, then all row coordinates, then all column coordinates, and finally regroups that coordinate stream into new triples. Each new triple is read back from the cube to produce the ciphertext. Decryption reverses the process with the same keyword and alphabet, so both settings must match the original encryption.

When to use this tool

Use this Trifid cipher tool to encode plaintext, decode Trifid ciphertext, compare keywords, and study how three-dimensional coordinate fractionation spreads information across a message. The form supports encryption and decryption, a required keyword, automatic alphabet detection, and explicit alphabet selection.

Supported alphabets are English, German, Spanish, French, Italian, Portuguese, and Turkish. English and Italian use a 25-letter grid with J merged into I plus two numeric padding positions; Spanish fits the cube naturally with ñ; German, French, Portuguese, and Turkish use language-specific merges so their alphabets fit exactly into 27 cube cells.

The tool strips spaces, punctuation, and unsupported characters before processing, then returns the result in uppercase. It is ideal for learning classical cryptography, checking hand calculations, preparing examples, and testing how keyword changes alter the Trifid cipher alphabet cube.

FAQ

The Trifid Cipher is a classical fractionating cipher invented by Félix Delastelle. It uses a 3×3×3 Polybius cube to represent each letter as three coordinates, then mixes those coordinates across the message to achieve stronger diffusion than the Bifid cipher.

Bifid uses a 2D Polybius square giving each letter two coordinates. Trifid uses a 3D Polybius cube giving each letter three coordinates. The three-stream coordinate mixing achieves greater diffusion, making Trifid harder to cryptanalyse than Bifid.

For English and Italian alphabets, two numeric pad characters (1 and 2) fill the 3×3×3 cube to exactly 27 positions. When the recombined coordinate triples map to those padding positions, digits appear in the ciphertext. They are correctly handled during decryption.

Yes. You must use the same keyword and the same alphabet as during encryption. The keyword determines the order of letters inside the 3×3×3 cube.

The online Trifid encoder and decoder supports English, German, Spanish, French, Italian, Portuguese, and Turkish. You can choose an alphabet manually or leave the setting on auto detection.

They are ignored during calculation. The Trifid cipher works on letters from the selected alphabet, applies the required letter merges for that alphabet, and returns an uppercase result without spaces or punctuation.
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