Wednesday, February 15, 2017

Crypto Box Challenge Solved by George Lasry

George Lasry
Great news from the Crypto Box Challenge, as George Lasry from Israel solved the final box! He's only the sixth person in more than nine years to complete the challenge. He took on the challenge in 2013 and, after various side tracks, including the completion of the Enigma Challenge, he succeeded cracking that last box.

George Lasry is a one.of-a-kind hobby cryptologist who evolved quickly into a well respected member of the classical cryptology community within a mere three years. It's the amazing story of a man who was searching for a new job in software development. Meanwhile, he wanted to train his programming skills and his interest in the Enigma machine lead him to the crypto challenges on my website. The Crypto Boxes were his first encounter with historical cryptography but the final box however proved a nut too hard to crack.

Giving up was not his cup of tea, so he started experimenting with various cryptanalytic techniques and quickly solved the complete Enigma Challenge with software he developed on his own. In search of new challenges he learnt about many cryptanalytic techniques and implemented various different types and combinations in his ever expanding software. Some other side tracks were the Mystery Twister C3 and the strong Double Transposition Challenge.

Searching a solution to a complex cipher is not simply writing some software to search for the solution or the proper key. It involves the development of complex fast algorithms for an exhaustive search, tailored for a specific problem, in combination with various methods to measure the success of the ongoing process and to proceed on a successful track.

The Crypto Box
He experimented with hill climbing, simulated annealing and used bigrams, trigrams, quadgrams and log quadgrams. A recent paper by Olaf Ostwald and Frode Weierud, Modern Breaking of Enigma Ciphertexts, explained the use of hexagrams. George had excellent results with this technique but the final Crypto Box remained unbroken. George finally solved the stubborn box on 14 February with a variation of simulated annealing, based on James Cowan's "churn" method, and even found three different keys to solve the box.

His journey through classical cryptology also draw the attention of some experts. George teamed up with German researchers and was encouraged to publish his techniques in the renowned Cryptologia journal. He started a PhD thesis and continued to solve various tough crypto challenges. His solution of the Double Transposition cipher caught the eye of people from Google, which eventually lead to his recruitment by Google.

I'm quite pleased to hear from George that my Crypto Box Challenge was his first encounter with classical cryptography and that the website inspired him to experiment with various cryptanalytic techniques, resulting in the successful decryption of the final Crypto Box. Congratulations George!

More about the challenges at Cipher Machines and Cryptology.

1 comment:

George Lasry said...

Many thanks Dirk, this is very kind of you. I appreciate very much your hard work and passion building your wonderful site, and setting up those outstanding challenges, which I enjoyed immensely. I hope you will consider publishing some sequels with additional Cryptobox challenges, which solutions may require breaking new limits with interesting algorithms.

While I am proud to be one of the only 6 people who solved the Cryptobox-1 challenge, and one of many other whole solved the Enigma challenge, the glory still goes to the pioneers who solved them first, and at the top, Olaf (Cryptobox) and Jean-Francois Bouchaudy (Enigma).

Many thanks again, looking forward to solving more of your great challenges.

George Lasry