In the early 1960s, National Security Agency cryptanalyst and cryptanalysis instructor Lambros D. Callimahos coined the term “Stethoscope” to describe a diagnostic computer program used to unravel the internal structure of pre-computer ciphertexts. The term appears in the newly declassified September 1965 document Cryptanalytic Diagnosis with the Aid of a Computer, which compiled 147 listings from this tool for Callimahos’s course, CA-400: NSA Intensive Study Program in General Cryptanalysis. The listings in the report are printouts from the Stethoscope program, run on the NSA’s Bogart computer, showing statistical and structural data extracted from encrypted messages, but the encrypted messages themselves are not included. They were used in NSA training programs to teach analysts how to interpret ciphertext behavior without seeing the original message...

The NSA and GCHQ have jointly published a history of World War II SIGINT: “Secret Messengers: Disseminating SIGINT in the Second World War.” This is the story of the British SLUs (Special Liaison Units) and the American SSOs (Special Security Officers).

“Fifty Years of Mathematical Cryptanalysis (1937-1987),” by Glenn F. Stahly, was just declassified—with a lot of redactions—by the NSA. I have not read it yet. If you find anything interesting in the document, please tell us about it in the comments.

In “Secrets and Lies” (2000), I wrote: > It is poor civic hygiene to install technologies that could someday facilitate > a police state. It’s something a bunch of us were saying at the time, in reference to the vast NSA’s surveillance capabilities. I have been thinking of that quote a lot as I read news stories of President Trump firing the Director of the National Security Agency. General Timothy Haugh. A couple of weeks ago, I wrote: > We don’t know what pressure the Trump administration is using to make > intelligence services fall into line, but it isn’t crazy to ...

2006 AT&T whistleblower Mark Klein has died.