Combined plaintext-plus-ciphertext self-keying cipher (Callimahos form)

A self-keying cipher whose key is the sum of an earlier plaintext letter and an earlier ciphertext letter (a form described by Callimahos), tried with short starting keys and named keywords. It was run on the carved text and on filler-letter models. The best, 11 of 24 known letters, came from an optimizing search over which letters are filler, where scores that high are expected by chance.

In plain English: A self-keying cipher whose key is the sum of an earlier plaintext letter and an earlier ciphertext letter (a form described by Callimahos), tried with short starting keys and named keywords, using a self-keying (autokey) method, where the key starts with a short word and then continues with letters of the message itself. Best match: 11/24 known letters, a level that searches like this can reach without the right key. This record is negative within the tested scope.

NOISE

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: N/A
Best Score: 11 / 24 known letters matched · can occur by chance in searches like this
Confidence: Not classified.
Date Tested: 2026-04-03
Script: scripts/substitution/e_combined_ptct_autokey.py

Reproduce

PYTHONPATH=src python3 -u scripts/substitution/e_combined_ptct_autokey.py

Requires the kryptos repo, Python 3.11+, PYTHONPATH=src. Some recent scripts may not be in the public repository yet.

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