King David High School

"Let there be light
through faith and work"

Maths Society ... Enigma

Enigma and the Secret World of Codes

Students from Year 10 and Year 12 attended a Liverpool Mathematical Society Lecture on Enigma and The Secret World of Codes and Codebreaking.  The speaker, Dr James Grime, provided a brief history of codes and code breaking, introducing the audience to the Caesar Shift and General Substitution Ciphers.  He then explained how a combination of logic and mathematical methods can be used to break codes.  Dr Grime had a loan of an Enigma Machine owned by Simon Singh (author of Fermat's Last Theorem and the Cracking Code Book) and shared its operation with the group.  It basically comprises of 2 typewriter style keyboards (one for the message and one for the code) linked by 3 rotors and bulb and a battery!  As each key is pressed the rotor turns and a different letter on the 2nd keyboard lights up.  The code can then be written down, passed along a chain, and then decoded by the operator of another Enigma Machine. Dr Grime described the work of Alan Turing and the Bombe Machine (at Bletchley Park) which broke the codes, potentially shortening World War II and thus saving lives.  In the latter part of the letter, Dr Grime described modern internet encryption methods used by banks. The product  of two very large prime numbers is a component of the RSA key.  After the lecture the Year 12 students were invited to stay for a code-breaking workshop.