For The Love of Ciphers: Love and War — The Nihilist Cipher

The usage of ciphers is often reserved for two places … in love and in war. For love, one of the best know ciphers was used by Mary Queen of Scots to sent secret messages to Anthony Babington. Unfortunately it was a weak cipher and was easily broken [Try a cipher]:

Cryptographers soon realised that simple frequency analysis could reveal the code mapping. So they looked towards the usage of a secret key, and which changed the output of the cipher stream. One of the best was used by Russian Nihilists in the 1880s and is known as the Nihilist cipher. They used it to organise terrorism activities against the Tsarist regime.

It works with two keys. Let’s take an example with a key of “HELLO”, and a message of “WELCOME”. We will use an additive key of “TEST”. First we first create a Polybius square with the key written first:

1 2 3 4 5
1 H E L O A
2 B C D F G
3 I K M N P
4 Q R S T U
5 V W X Y Z

We convert the message into the grid values:

PT:  W  E  L  C  O  M  E
    52 12 13 22 14 33 12

And do the same of the additive key:

Add Key: T E  S  T
        44 12 43 44

We then add the plain text value to the key value to get:

52 12 13 22 14 33 12
44 12 43 44 44 12 43 
---------------------
96 24 56 66 58 45 55

The cipher text is 96245666584555. Notice that the ‘e’ character has two different mappings (24 and 55). My calculator for the ciphering process is here.

Okay … do you now want to try to create your own Nihilist cipher try here:

Nihilist cipher