Automated Ciphertext - Only Cryptanalysis of the Bifid Cipher

In this paper we describe a fully automated ciphertext-only cryptanalysis attack on the Bifid cipher, for which the original text language is known. We have implemented this attack using Python. We use an easily computable statistical function to find the period of the cipher, and then the key-table is generated in a fairly efficient way. The process is directed in such a way that strongly narrows the search space of possible solutions. This results in a feasible attack to a Bifid cryptogram, provided that its length is enough for accurate statistical analysis.