# Gromark cipher · Concept

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

Source: https://mysteriesdept.com/concepts/CPT0DECW00HS0D8/gromark-cipher  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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[Concepts](https://mysteriesdept.com/concepts)Gromark cipher

Concept · cryptography · in 1 mystery

# Gromark cipher

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

[Kryptos](https://mysteriesdept.com/mysteries/kryptos)

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](https://mysteriesdept.com/mysteries/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…](https://mysteriesdept.com/mysteries/kryptos/answers/ANS0D7HTBYY64KH/k4-uses-a-gromark-type-cipher-a-keyed-alphabet-with-a)[Monte Carlo permutation tests show a strong one-to-one relation between corresponding plaintext and…](https://mysteriesdept.com/mysteries/kryptos/evidence/EVD0D7HTC6R3ASK/monte-carlo-permutation-tests-show-a-strong-one-to-one)

## Cite it

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

Key

**CPT** 0DECW00HS0D8

Record

Concept

Field

Cryptography

Related

[Keyed alphabet](https://mysteriesdept.com/concepts/CPT0DECW00PYYD3/keyed-alphabet) · [Vigenère cipher](https://mysteriesdept.com/concepts/CPT0DECW00CABZA/vigenere-cipher) · [Crib](https://mysteriesdept.com/concepts/CPT0DECW00XAZGK/crib)

Version

2

Added by

[apollo](https://mysteriesdept.com/u/apollo)

**How this page is made.** The definition is the site's, in its own words. “Where it comes up” is read from the answers, methods and evidence that name the concept.

Related concepts

[Keyed alphabet](https://mysteriesdept.com/concepts/CPT0DECW00PYYD3/keyed-alphabet)[Vigenère cipher](https://mysteriesdept.com/concepts/CPT0DECW00CABZA/vigenere-cipher)[Crib](https://mysteriesdept.com/concepts/CPT0DECW00XAZGK/crib)

The record

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