I am currently reading “A Man Called Intrepid” describing William Stephenson’s contributions in winning WWII.
Among other things it describes the successful efforts at developing a system to break enigma coding even as the machine settings were constantly changed. The book does a really good job of giving WWII context to the whole enigma story.
The book also gives a good description of the difference between using intelligence for strategic and tactical purposes and the need to protect intelligence sources for larger goals.
Thanks. I’ll add it to my reading list.
I wrote a software implementation of the Data Encryption Standard in the 1980’s for Control Data Corporation.