Trifid Cipher
Bifid extended to three dimensions — the 3×3×3 cube
Why This Matters
Delastelle’s Trifid extended the Bifid into three dimensions — using a 3×3×3 cube instead of a 5×5 square — achieving even greater diffusion by weaving three coordinate streams together before converting back to letters.
Delastelle extended his Bifid cipher one year later by adding a third dimension. Where Bifid used a 5×5 square (25 cells for 25 letters, I/J shared), Trifid uses a 3×3×3 cube (27 cells for 26 letters plus one null). Each letter becomes three coordinates: layer, row, and column. These three streams are woven together across the message before being converted back.
3×3×3 cube: each letter has coordinates (layer, row, col) A=(1,1,1) B=(1,1,2) C=(1,1,3) D=(1,2,1) E=(1,2,2) F=(1,2,3) ... HELLO encrypted: 1. Get L,R,C coordinates for each letter 2. Write all L values, then R values, then C values 3. Group into triples, look up in cube
The three-dimensional fractionation creates stronger diffusion than Bifid. Each ciphertext letter depends on three plaintext letters' coordinates woven together. Modern solvers use hill climbing with trigram statistics but require more ciphertext than Bifid attacks.
| Concept from Trifid Cipher | Modern Evolution |
|---|---|
| 3D coordinate system | Multi-dimensional bit manipulations in modern hash functions |
| Three-stream interleaving | AES: 4 operations per round create multi-dimensional diffusion |
| Larger coordinate space than Bifid | Increasing output size increases security: SHA-256 vs SHA-512 |
| Exhibit | 16 of 37 |
| Era | 1902 |
| Security | Broken |
| Inventor | Felix Delastelle |
| Year | 1902 |
| Key Type | 3×3×3 keyword cube |
| Broken By | Statistical analysis |