Trifid Cipher
Bifid extended to three dimensions — the 3×3×3 cube
Statistical analysis
Why This Matters
Delastelle’s Trifid uses three coordinates per symbol. Concatenating and regrouping those coordinates mixes information across a chosen period. The method is a useful comparison with Bifid, but three dimensions alone do not prove stronger security for every parameter choice.
Delastelle’s Trifid uses a 3×3×3 arrangement, giving 27 symbols, and combines three coordinate streams. His posthumous 1902 treatise describes the method. The extra symbol may be a period or another agreed symbol; it is not inherently a null that must be discarded.
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
Three-coordinate fractionation changes how information is mixed across a block. Exactly which plaintext positions influence an output depends on the period and layout. A third coordinate alone does not prove that Trifid always requires more ciphertext to attack than Bifid.
| Concept from Trifid Cipher | Modern Evolution |
|---|---|
| 3D coordinate system | Multi-dimensional bit manipulations in modern hash functions |
| Three-stream interleaving | AES combines nonlinear substitution and linear mixing; its final round omits MixColumns |
| Larger coordinate space than Bifid | Larger representation size alone does not establish greater cryptanalytic strength |
| Exhibit | 17 of 172 |
| Era | 1902 |
| Trust | Broken |
| Inventor | Felix Delastelle |
| Year | 1902 |
| Key Type | 3×3×3 keyword cube |
| Broken By | Statistical analysis |
Sources and Reading
Helen Fouché Gaines, Cryptanalysis: A Study of Ciphers and Their Solution (1939; Dover reprint 1956), Chapter XXII; David Kahn, The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet, revised edition (1996), on Delastelle’s posthumous Traité élémentaire de cryptographie (1902).