Native 28×31 grid reading orders + periodic substitution on 73-char extract

Tested 10+ native grid reading orders (column-by-column L→R/R→L, serpentine columns/rows, diagonal TLBR/TRBL, spiral CW, paired mirror columns, row-reversed) × Vig/Beau/VBeau × periods 1-26 on 73-char column mask extract. Also tested on full 97-char text with grid column reading. 2,262 configs on 73-char, best 22/24 at serpentine_row/beaufort/p24 = UNDERDETERMINED NOISE (period 24 with 24 cribs means each residue class has ≤1 crib position). Full 97-char: best 20/24 at p25.

In plain English: Tested 10+ native grid reading orders (column-by-column L→R/R→L, serpentine columns/rows, diagonal TLBR/TRBL, spiral CW, paired mirror columns, row-reversed) × Vig/Beau/VBeau × periods 1-26 on 73-c — using a combined approach: scramble the letter order AND replace each letter. Every possible combination was tested (2 thousand configurations) — none produced a valid solution. Best match: 22/24 known letters (statistically expected at this key length, not a real signal). This approach is ruled out within the tested scope.

NOISE: all high scores at high periods (underdetermined). Discriminating periods (≤7): max ~12/24 Tier 2

How to read this record

Verdict – NOISE (no better than random guessing), INTERESTING (slightly above random, almost certainly coincidence), SIGNAL (statistically unusual, warrants investigation), or FULL MATCH (all 24 known letters correct).
Confidence Tier – Tier 1 = mathematical proof (permanent). Tier 2 = every possibility tested. Tier 3 = partially tested. Tier 4 = not yet tested.
Configs Tested – How many different key/parameter combinations were tried.
Best Score – How many of the 24 known plaintext letters the best attempt matched (out of 24).
Keystream Consistency (Bean) – Whether the key values at different positions are mathematically consistent with each other.
Scope Limitations – What this elimination does not rule out.

Configs Tested: 2,262
Best Score: 22 / 24 known letters matched · worth investigating (random guess would score: 0.0)
Keystream Consistency (Bean): FAIL
Checks whether the key values at different positions are mathematically consistent with each other.
Confidence: Tier 2: Exhaustive search under stated assumptions. Does not eliminate multi-layer variants.
Truth Tag: [INTERNAL RESULT]
Date Tested: 2026-03-12

Scope Limitations

This elimination does not rule out:

Only tests periodic substitution after grid reading transposition. Non-periodic ciphers with grid reading remain open.

Assumptions

28×31 native grid layout
Column mask null removal
Reading order = transposition
Periodic substitution

Reproduce

PYTHONPATH=src python3 -u scripts/grille/e_native_grid_reading_01.py

Requires the kryptos repo, Python 3.11+, PYTHONPATH=src.

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