Simply Turing

Michael Olinick

• Éditeur: Simply Charly
• Année: 2021
• ISBN:
  9781943657384
• Sujet: Technology & Engineering
• Sous-sujet: Science & Technology Biographies

"Michael Olinick has written a vibrant and absorbing biography of Alan Turing. Turing's work as a cryptographer during WW II and his pioneering development of the digital computer helped us win that war and make our technology-driven world of today possible—all this against the backdrop of the homophobic world Turing tried to navigate."
— Joseph Malkevitch, Professor of Mathematics at York College (CUNY) and CUNY Graduate Center

Alan Turing (1912-1954) was born in London and showed signs of genius from a very young age. Turing was just 24 when he devised the theory that led to the development of modern computers and he went on to achieve major breakthroughs in probability, number theory, cryptology, and mathematical biology. His codebreaking efforts during World War II allowed the British to decipher secret German communications, effectively shortening the war and saving millions of lives. Yet instead of being celebrated for his accomplishments, Turing was prosecuted for being a homosexual and was forced to undergo hormone treatments designed to reduce his sexual drive. Turing died of cyanide poisoning in 1954 at the age of 41, a tragic end to a brilliant life, and an event that remains mysterious to this day.

In Simply Turing, Professor Michael Olinick recounts the life and work of a man who, along with Newton and Darwin, is considered one of the three most influential British scientists of all time. Prof. Olinick provides an accessible explanation of Turing's monumental achievements, while introducing us to the friends, colleagues, and rivals who shared his life, and exploring the controversy surrounding his death.

For anyone interested in the beginnings of our computer-defined age, or anyone who wants a better understanding of why LGBTQ rights are so important, Simply Turing is an indispensable and fascinating introduction to a man who was both ahead of his time and a tragic victim of it.

6

Cryptology From Caesar to Turing

Cryptology is the study and practice of secret communication. The need to conceal from others messages between a sender and an intended receiver traces back to the earliest human civilization. To place Turing’s contributions in an appropriate context, we will review some important milestones in the history of cryptology.

We can divide cryptology into two categories: cryptography and cryptanalysis, essentially codemaking and codebreaking. Cryptography focuses on creating secure communication, while cryptanalysis is the effort to decipher intercepted messages.

The primary goal of cryptography is rendering a discovered message unintelligible to anyone but the intended recipients. We call the original form of the message plaintext and the disguised form ciphertext. There are two principal means of converting plaintext into ciphertext: transpositions and substitutions.

In a transposition, each letter in the ciphertext represents itself but does not appear in the same position as in the plaintext. Writing each word in the plaintext backwards to create the ciphertext is one example. Another is the “picket fence transposition,” where all the letters in an odd position in the plaintext precede all the letters in an even position. A transposition simply rearranges the order of the letters in a message.

In contrast to transposition, substitution replaces each letter or block of letters by a different set of letters. Substitutions are of two types: codes and ciphers. A code is a mapping from some meaningful unit in the plaintext, such as a word, sentence, or phrase, into something else. We might map each word or phrase in an ordinary dictionary to a different five-digit number, using a two-part code book. The first part lists each word or phrase in alphabetical order followed by a number. The second part lists the numbers first in order, followed by the corresponding word or phrase. Here is a code book with an extremely limited vocabulary:

Part I			Part II
AT DAWN	20912		ATTACK	02472
ATTACK	02472		IS	05753
IS	05753		AT DAWN	20912
OUR	53705		PLAN	48237
PLAN	48237		OUR	53705
TO	75248		TO	75248

We can use this artificial example to illustrate how we would encode the plaintext

OUR PLAN IS TO ATTACK AT DAWN

OUR	PLAN	IS	TO	ATTACK	AT DAWN
53705	48237	05753	75248	02472	20912

The ciphertext wou...