Alan Turing - an overview

Alan Turing first introduced the Turing machine in 1936 in his paper "On Computable Numbers, with an Application to the Entscheidungsproblem." The Turing machine is a simple yet abstract machine, more precisely a mathematical model. It consists of a potentially infinite two-dimensional tape divided into cells, each capable of holding a single symbol, a movable read-write head, and a defined internal state. Turing machines represent an algorithm or a program that they execute. Despite their simple construction, Turing machines are computation-universal, meaning they can perform any function that is computable in the intuitive sense. They also model the operation of physical computers in a simplified manner.

Cryptanalysis originally refers to the study of methods and techniques to extract information from encrypted texts. Alan Turing worked at Bletchley Park to decipher the Enigma, the encryption machine used by the Nazis during World War II. This device operated similarly to a typewriter; plaintext was input, resulting in encrypted text output. When a letter was entered on the keyboard, it passed through three rotors that scrambled the alphabet. For example, the first rotor might transform A into L, the second L into Z, and the third Z into P, coding A as P. With each letter entered into the Enigma, the rotors shifted to a new setting, altering the coding for the next letter. With its 150 million possibilities, the Enigma was considered unbreakable at the time. Cryptanalytic calculations drastically reduced this number, but around one million possibilities still had to be tested by codebreakers. The initial task was to discover the base settings used by the Germans, such as which rotors were installed in which positions. However, the Germans changed these base settings daily, forcing the codebreakers to start anew each day. Turing interconnected several Enigma machines to determine the correct daily settings through trial and error. This machine was called the Turing Bombe. Turing's work has been depicted in numerous Hollywood films, such as "The Imitation Game," with Benedict Cumberbatch portraying Alan Turing.

Alan Mathison Turing is one of the most important mathematicians and computer scientists of the 20th century. His theoretical work and dissertations focused on mathematical questions and problems. In his early twenties, he laid the foundation for modern computer science. Without his groundbreaking concept of the Turing machine, today's computers would not exist, and most programs would not be executable. Additionally, the Turing Tests he designed are still used in artificial intelligence research today. Turing was also a pioneer in the field of cryptanalysis. His work at Bletchley Park and the successful decryption of the Enigma machine were crucial turning points in World War II in favor of the Allies. Deciphering secret German communications contributed to the Allied victories in the Battle of the Atlantic and in North Africa. In 2014, Turing was inducted into the Hall of Honor of the U.S. National Security Agency (NSA), which was established in 1999 to honor individuals who made significant contributions or pioneered U.S. cryptology.

Turing is also known for his homosexuality and the forced chemical castration he endured, making him a symbol of the inhumane criminal prosecution of homosexuals. In 2009, around 30,000 Britons signed an online petition submitted to the government, demanding a posthumous apology and rehabilitation for Turing. The government initially concluded that this was not possible, as the conviction was considered lawful at the time. However, on December 24, 2013, Turing was granted a Royal Pardon by Queen Elizabeth II, effectively rehabilitating him. In January 2017, Queen Elizabeth II enacted a law that, building on Turing's pardon, annulled the punishment for all homosexual men if, at the time, both were over 16 years old and had engaged in consensual acts.

In conclusion, it can be stated that Alan Turing, alongside figures like Albert Einstein or Stephen Hawking, is one of the most brilliant and influential scientists of the modern era. His legacy ignited the debate over the criminal prosecution of certain sexual orientations, leading to increased rights for homosexuals in the United Kingdom.