Is K4 solved, known but withheld, or open?
Answered: K4 is solved; its plaintext has been recovered and confirmed by its author.Passed its tests and review.
Where it stands
Four answers have been proposed. K4 is solved; its plaintext has been recovered and confirmed by its author. leads, with evidence 1 for, 2 against: partly supported by its tests. Three are still possible. Of the one narrower question under it, none is answered yet.
Answers 4
History
- Bean: no peer-reviewed or verified decryption of K4 exists; published work is diagnostic.For: K4 remains unsolved as a cryptographic problem; no one has derived its plaintext and method from the…
- Schwartz puts forward: k4 is solved; its plaintext has been recovered and confirmed by its author.
- RR Auction puts forward: k4 remains unsolved as a cryptographic problem; no one has derived its plaintext and method from the…
- Agence France-Presse: sanborn says the find gave the plaintext but not the coding method or the key, which he calls a very…Against: K4 is solved; its plaintext has been recovered and confirmed by its author.
- Escoria & Maren: kobek himself says the find is not a cryptographic solve.Against: K4 is solved; its plaintext has been recovered and confirmed by its author.
- Schwartz: kobek and Byrne assembled a plaintext from archive scraps that matched the released clues in length and…For: K4 is solved; its plaintext has been recovered and confirmed by its author.
- RR Auction: the archive sold on 20 November 2025 included Sanborn's handwritten K4 plaintext and the original K4 coding…For: K4's plaintext and method are known to a few holders and deliberately unpublished.
- Agence France-Presse: kobek and Byrne refused NDAs but say they will not publish, after letters from the auction house's lawyers.For: K4's plaintext and method are known to a few holders and deliberately unpublished.
- Basilio: the Smithsonian sealed the relevant files for fifty years at Sanborn's request.For: K4's plaintext and method are known to a few holders and deliberately unpublished.
- Vergano: sanborn's position after the find is that K4 has not been solved and that it points toward K5.For: K4 remains unsolved as a cryptographic problem; no one has derived its plaintext and method from the…
- Robinson & Huang puts forward: k4's plaintext and method are known to a few holders and deliberately unpublished.
- Robinson & Huang: paradigm says Sanborn entered the plaintext into a verifier and that the firm has not seen it; it has not…For: K4's plaintext and method are known to a few holders and deliberately unpublished.
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