The Ciphertext
97 Unsolved Characters
Systematic Elimination
What K4 Is NOT
Each row represents a cipher family tested to destruction against the 24 known plaintext characters.
| Cipher Family | Status | Evidence |
|---|---|---|
| Simple Monoalphabetic | ✗ Eliminated | Mapping contradiction at known positions for every transposition (0/13,136 consistent) |
| Affine Cipher | ✗ Eliminated | No valid (a,b) pair satisfies 24 known positions |
| Autokey Vigenère | ✗ Eliminated | Zero consistent configurations across all transpositions |
| Gromark Cipher | ✗ Eliminated | 22,000 primers (2-5 digit seeds), all fail at anchors |
| Hill 2×2 Cipher | ✗ Eliminated | 157,248 invertible matrices tested, zero produce ≥16 anchor matches |
| Single Vigenère | ✗ Eliminated | No single period satisfies all 4 anchor groups simultaneously |
| Carter Diary Running Key | ✗ Eliminated | Full Nov 26, 1922 diary — 147K attempts, best 7/24 = noise |
| Carter Journals (All 3 Seasons) | ✗ Eliminated | 77K alpha chars from Griffith Institute — 5M+ attempts, best 8/24 = noise |
| K1-K3 Plaintexts as Key | ✗ Eliminated | Direct running-key test, no anchor matches |
| Mathematical Key Derivation | ✗ Eliminated | Coordinates, Fibonacci, primes, modular, positional — none fit forced key |
| Pure Playfair | △ Unlikely | 97 chars (odd), double letters (BB, SS), best 7/9 partial match |
| Pure Four-square / Two-square | △ Unlikely | No anchor matches under any keyword configuration |
| Polyalphabetic + Transposition | ? Possible | Consistent configs exist but no English plaintext outside anchors |
| Running Key (Unknown Source) | ? Possible | Key appears text-derived — source not yet identified |
| Modified Vigenère | ? Possible | "Make the Vigenère more abstruse" — per Scheidt |
| 3+ Layer Compound | ? Untested | Every 2-layer combo searched; third layer not yet attempted |
Analysis
Key Findings
The Forced Key
BLZCDCYYGCKAZMUYKLGKORNA
Under Vigenère, the 24 known plaintext chars force these key values. No mathematical function (linear, quadratic, Fibonacci, prime, coordinate-derived) fits them. The key is almost certainly text-derived.
Period-26 Near-Miss
With key length 26, only 1 conflict exists (B vs A, off by exactly 1). 23 of 26 key slots are determined. Periods 27-29 have zero conflicts but more unknowns. This could indicate a Quagmire variant with nonstandard indexing.
K3 ≠ Carter Diary
Sanborn made 9 deliberate creative changes when adapting Carter's diary for K3: changed pronouns (we→I), substituted words (top→upper, candle→flame), added emotional phrases. These are artistic choices, not errors.
IC Below Random
K4's Index of Coincidence (0.036) is below pure random (0.038), far below English (0.067). This suggests multi-layer encryption or a very long/random key.
Arsenal
40 Strategies
Each strategy is a standalone Python script producing structured JSON output.
Discovery
Sanborn's Creative Changes to the Carter Diary
| K3 Plaintext | Actual Diary | Change |
|---|---|---|
| I MADE A TINY BREACH | WE MADE A TINY BREACH | we → I |
| IN THE UPPER LEFT HAND CORNER | IN THE TOP LEFT HAND CORNER | top → upper |
| I INSERTED THE CANDLE AND PEERED IN | I WIDENED THE BREACH AND BY MEANS OF THE CANDLE LOOKED IN | Simplified |
| THE FLAME TO FLICKER | THE CANDLE TO FLICKER | candle → flame |
| PRESENTLY DETAILS ... EMERGED FROM THE MIST | ONE'S EYES BECAME ACCUSTOMED TO THE GLIMMER OF LIGHT ... | Complete rewrite |
| SLOWLY DESPARATLY SLOWLY | (not in diary) | Added by Sanborn |
| WITH TREMBLING HANDS | (not in diary) | Added by Sanborn |
Open Questions
What Could K4 Be?
Modified Vigenère + Transposition
The leading hypothesis. Consistent configurations exist, but no key source has been identified. Ed Scheidt confirmed methods from Friedman's Military Cryptanalysis texts.
Unknown Running Key Source
The forced key values look random — exactly what a running key from natural text produces. Carter is eliminated. Untested: Friedman's texts, Sanborn's other sculptures, CIA documents.
Three or More Layers
Every two-layer combination has been searched. A third layer (fractionation, additional transposition) could explain the below-random IC.
Sanborn's Own Invention
Something close to but not exactly standard Vigenère. The ±1 offset at period 26 could be a signature of a modified algorithm.