Chaocipher

The Chaocipher – A Devious Cipher System

The Chaocipher is a devious cipher system which was invented by John F. Byrne in 1918. Byrne was born in Ireland and was a close friend of the famed authorJames Joyce and an unlikely candidate for devising a strong cryptosystem. The Chaocipher is a machine cipher which was not defeated for ninety years till the family of the inventor made the author’s paper known, describing the algorithm for his simple two disk machine.

It was alleged to be so complex that no one could understand his challenged cipher text yet was so simple that its mechanism claimed to comprise of only two rotating disks which were small enough to be accommodated in a cigar box. This could be operated by a ten year old, probably a diligent, determined and a well-practised one to encipher and decipher texts. `Chaocipher’, is the name which was given by Byrne to a cipher system invented by him and from its inventions to his death, he persistently tried to draw the interest of governments as well as organization to use his system. More can be available from National cryptologic museum .

Failed to be Taken Seriously

His system, unfortunately failed to be taken seriously by those whom he approached which was due to Byrne’s refusal in providing William F. Friedman with the standard number and type of challenge messages that were requested from each cipher inventor that approached the US military organizations. Byrne published his autobiographical `Silent Years’, in 1953 wherein the book contained much on his memories of James Joyce, though the purpose of writing the book was to publicize Chaocipher to the world. The twenty first chapters in `Silent Year’s comprises of plenty of plain texts with corresponding cipher-text, more than normally expected. Besides this, there are a few enciphered lines with no plain-text provided and Byrne has challenged the world at large to decipher these lines.

Interesting for Several Reasons 

The cipher was interesting for several reasons, the first being that Byrne published four texts with their cipher equivalents, which amounted to a total over 10,000 letters challenging the world to evaluate the workings of his machine with no success and the amateur cryptanalysts got nowhere to any solution. Secondly, the algorithm had been made public and the keys for only two of the four texts have been recovered. The keys that were used for the other two remains a challenge yet to be solved.

The third point of interest is that Byrne in 1920 had worked with a profession draughtsman, producing a design for a fully mechanised enciphering machine with a keyboard which was never built due to its high cost though the original drawings are available and not the description of the machine. The working of the machine still remains a mystery.

The last interesting fact is that the professional cryptanalysts rejected Chaocipher as of no importance and did not express their reasons in public. One such notable critic was William F. Friedman, the leading US cryptanalyst of the 30s and 40s though some current opinion consider the algorithm of Chaocipher as a clever idea to provide strong, reliable and unbreakable cipher when implemented on a computer. The same has not been solved till date and continues to be one of the premier unsolved ciphers providing a challenge to the present generation.