TheCodeBreakers
The popular cipher that the checkerboard inspired is named for the
Nihilists, the anarchistic opponents of the czarist regime, who may have
invented it. The Nihilist cipher converts both the plaintext and a
repeating keyword into numerical form via the checkerboard, and then
adds them together to produce the ciphertext. If the keyword is ARISE, or
11 42 24 43 15, the plaintext Bomb Winter Palace would be enciphered
like this:
literal plain numerical plain key
ciphertext
bombwinterpalace 12 34 32 12 52 24 33 44 15 42 35 11 31 11 13 15
11 42 24 43 15 11 42 24 43 15 11 42 24 43 15 ll
23 76 56 55 67 35 75 68 58 57 46 53 55 54 28 26
Occasional three-digit groups will occur, as 55 -j- 54 = 109. The
cipher is a kind of modified numerical Vigenere with additional
weaknesses that simplify solution. It would not have baffled an expert
very long. Yet this basic system—the adding of a key to a checkerboard
substitution, though with important improvements—survived through
annaabi.ee 
