Vigenère cipher

A substitution cipher that shifts each letter by a key word's letters in turn.

The classic polyalphabetic cipher: each letter of the plaintext is shifted by the corresponding letter of a repeating key word. Kryptos K1 and K2 are Vigenère ciphers with a keyed alphabet, solved in the 1990s. Its weakness is the repeat, which period tests find; its descendants on this site, running-key and Gromark ciphers, were built to remove it.

Where it comes up

Kryptos

K1 and K2 are Vigenère ciphers on a tableau keyed with KRYPTOS; K3 is a transposition.

Cite it

Mysteries Department. (2026). Vigenère cipher [Concept CPT0DECW00CABZA]. https://mysteriesdept.com/r/CPT0DECW00CABZA

@misc{mysteriesdept_cpt0decw00cabza,
  title     = {Vigenère cipher},
  author    = {{Mysteries Department}},
  year      = {2026},
  note      = {Concept, catalog key CPT0DECW00CABZA},
  url       = {https://mysteriesdept.com/r/CPT0DECW00CABZA}
}