All areas3 of 20 fields
Logic, Security, Computation cluster
Logic & Theory of Computation · Security & Cryptography · Computer Science & Early Computers
The bombe is an engineering answer to a search problem: the machine searches Enigma's rotor order, rotor settings and plugboard settings by chaining logical deductions from a crib and discarding every setting that produces a contradiction, leaving only a few for hand checking.
With Dilly Knox I developed a crib-based approach to Enigma that did not depend on the German indicator procedure, and I wrote the engineering specification of the bombe — the machine design behind the codebreaking technology. The first one was installed on 18 March 1940.
In my 1936 paper "On Computable Numbers" — mathematical research that founded the science of computation — I replaced Gödel's arithmetic-based formal language with simple hypothetical machines, defined a universal machine, and proved the halting problem undecidable, settling Hilbert's decision problem in the negative.
I work across mathematics, logic, cryptanalysis, computer design and theoretical biology. My best-known contribution is the Turing machine, a formal model of algorithm and computation that can stand in for a general-purpose computer.
