Nihilist Cipher - Nihilist Cryptanalysis

Nihilist Cryptanalysis

Because each symbol in both plaintext and key is used as a whole number without any fractionation, the basic Nihilist cipher is little more than a numerical version of the Vigenère cipher, with multiple-digit numbers being the enciphered symbols instead of letters. As such, it can be attacked by very similar methods. An additional weakness is that the use of normal addition (instead of modular addition) leaks further information. For example, (assuming a 5 × 5 square) if a ciphertext number is greater than 100 then it is a certainty that both the plaintext and key came from the fifth row of the table.