Nihilist cipher

English

Etymology

The cipher was originally used by Russian Nihilists in the 1880s to organise terrorism against the tsarist regime.

Noun

Nihilist cipher (plural Nihilist ciphers)

1. (cryptography, historical) A symmetric cipher in which a Polybius square using a mixed alphabet is used to convert both the plain text and a keyword to a series of two-digit numbers, which are then summed in the normal way to get the ciphertext, with the key numbers repeated as required; (by extension) any of several improved algorithms based on this.