speech-encipherment
The process of encoding speech signals into discrete digital streams for secure transmission, exemplified by the 'X-system' using multi-level quantization and modular addition with a random key.
2 chapters across 1 book
Alan Turing: The Enigma (1983)Andrew Hodges
The chapter chronicles Alan Turing's 1943 visit to the United States during World War II, focusing on his critical role in Anglo-American cryptanalytic collaboration, including breakthroughs in decrypting German U-boat Enigma communications and pioneering speech encipherment projects at Bell Labs. It highlights Turing's intellectual engagement with Claude Shannon, bridging cryptanalysis and information theory, while also exploring the moral complexities and cultural challenges he faced amid the evolving scale and impersonality of the war effort.
The chapter chronicles Alan Turing's post-1943 transition from wartime codebreaking to pioneering a new speech encipherment system, Delilah, at Hanslope Park. It details his mathematical approach leveraging the bandwidth theorem and modular addition to create a theoretically secure speech cipher, alongside the practical challenges of implementation and key generation. Concurrently, it highlights advancements in wartime cryptanalysis, notably the Mark II Colossus, which automated complex decision-making and significantly enhanced the decryption of German Fish signals.