Running-key scan using the two EASTs in the known plaintext (gap-9 key-difference filter)
A running-key scan of about 4 million letters of source text, using a fast filter based on the repeated EAST. EAST appears twice in the known plaintext, 9 letters apart, so for a running key applied directly to the carved text the key letters under the second EAST must differ from those under the first by a fixed pattern. 34 places passed the filter and none fitted all 24 known letters.
In plain English: A running-key scan of about 4 million letters of source text, using a fast filter based on the repeated EAST, using a passage from a book or document as the encryption key. Every combination within the stated scope was tested (4.0 million configurations); none produced a valid solution.
This record is negative within the tested scope.
NOISE
Tier 2
How to read this record
- Verdict – ELIMINATED (ruled out within the tested scope), NOISE (nothing beyond what chance produces for a search of this size; also shown when a record stored no verdict of its own), INCONCLUSIVE (the test left candidates or options standing, or could not decide, so it does not rule the method out), 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, valid while its stated assumptions hold. Tier 2 = every possibility within the stated scope tested. Tier 3 = partially tested or sampled. Tier 4 = not yet properly 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). N/A means no such score could be read from this record.
- Keystream Consistency (Bean) – Whether the key values at different positions are mathematically consistent with each other. The check only holds when the known letters stay in their carved positions (no letters rearranged or removed), and the full set used here assumes the standard A to Z alphabet.
- Scope Limitations – What this elimination does not rule out.
- Configs Tested
- 4,000,000
- Best Score
- 0 / 24 known letters matched · low, no sign of a solution
- Confidence
- Tier 2: Exhaustive search under stated assumptions. Does not eliminate multi-layer variants.
- Truth Tag
[INTERNAL RESULT]- Date Tested
- 2026-02-27
- Script
scripts/cfm/e_cfm_06_east_constraint.py
Scope Limitations
This elimination does not rule out:
- Running keys combined with a letter rearrangement, which changes the key differences the filter relies on
- Source texts not scanned
Assumptions
- Additive substitution (Vigenere/Beaufort/VB)
- Running key from contiguous text passage
Related Research Questions
Reproduce
PYTHONPATH=src python3 -u scripts/cfm/e_cfm_06_east_constraint.pyRequires the kryptos repo, Python 3.11+, PYTHONPATH=src. Some recent scripts may not be in the public repository yet.
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