Gromark cipher

A cipher that shifts each letter by a running numeric key made from a short seed.

A cipher in which a short numeric seed grows into a long running key by adding neighbouring digits, and each plaintext letter is shifted by the next key digit through a keyed alphabet. It never repeats within a message and resists the tests that break Vigenère. It is the leading family of readings for Kryptos K4, because the four released cribs fit it with a single keyed alphabet.

Where it comes up

Kryptos

K4 uses a Gromark-type cipher (a keyed alphabet with a running numeric key generated by chain addition) or a close relative.

K4 uses a Gromark-type cipher (a keyed alphabet with a running numeric key generated by chain addition) or a…Monte Carlo permutation tests show a strong one-to-one relation between corresponding plaintext and…

Cite it

Mysteries Department. (2026). Gromark cipher [Concept CPT0DECW00HS0D8]. https://mysteriesdept.com/r/CPT0DECW00HS0D8

@misc{mysteriesdept_cpt0decw00hs0d8,
  title     = {Gromark cipher},
  author    = {{Mysteries Department}},
  year      = {2026},
  note      = {Concept, catalog key CPT0DECW00HS0D8},
  url       = {https://mysteriesdept.com/r/CPT0DECW00HS0D8}
}