An NSA Codebreaker on Talking to Aliens: Callimahos, 1965
In 1965, NSA cryptanalyst Lambros Callimahos asked how humanity would read a message from another civilization. His answer was 'inverse cryptography,' and he wrote a sample alien transmission for colleagues to crack.
What this record is
This nine-page record is “Communication with Extraterrestrial Intelligence” by Lambros D. Callimahos, published in the NSA Technical Journal, Volume XI, Number 1. The Technical Journal was the agency’s in-house professional publication. This article is marked Unclassified. Callimahos was one of NSA’s best-known cryptanalysts and teachers. A footnote explains that the article is based on his talk at a panel discussion with the same title, held on 23 September 1965 during the IEEE Conference on Military Electronics in Washington, D.C. The catalog uses that date. According to the footnote, the other panellists were the linguist Paul Garvin, the dolphin researcher John C. Lilly, the physicist William O. Davis and the Jesuit astronomer Francis J. Heyden. The moderator was Harold Wooster of the Air Force Office of Scientific Research.
The article is not about UFO sightings. It is in the collection because it deals with extraterrestrial intelligence, and NSA listed it among its UFO-related holdings.
What it says
Callimahos opens with a confident claim: “We are not alone in the universe.” He cites Sir Bernard Lovell’s estimate that about 100 million stars in our galaxy should have suitable planets, and Frank Drake’s figure of about a billion civilizations that could have arisen so far. Then he asks, “Where is everybody?” He summarizes Project Ozma, Drake’s 1960 search of Epsilon Eridani and Tau Ceti. He explains why the 21-centimetre hydrogen line at 1420.405752 megacycles, proposed by Giuseppe Cocconi and Philip Morrison, is a natural listening frequency.
Most of the article treats contact as a cryptologic problem. He walks through Bernard Oliver’s 1,271-bit picture message, composed after the 1961 Green Bank meeting. Because 1,271 factors only into 31 and 41, a recipient would lay the bits out as a raster, and Callimahos interprets the resulting pictogram line by line. He compares Lancelot Hogben’s “Astraglossa” proposal of 1952 with Hans Freudenthal’s “Lincos” language of 1960, and concludes that most readers found Lincos too difficult. The key idea, he writes, is “inverse cryptography”: a symbol system designed “not to hide meaning, but to be as easy as possible to comprehend,” where the sender’s cleverness matters more than the recipient’s ingenuity.
He then gives his own example. It is a series of numbered transmissions made of arbitrary symbols separated by timed pauses, which starts with counting and arithmetic and builds up to words and concepts. He invites readers to work it out, and says that the reader who does so will be reading “pure Venerean” by the end. The article closes lightly. The first questions to put to “them” should be proofs of Fermat’s Last Theorem and Goldbach’s conjecture, and perhaps a discreet inquiry into how humans might live in peace, “that is, if we aren’t eaten.”
Context
The article belongs to the SETI thinking of the early 1960s rather than to UFO investigation. Its interest for this collection is that it shows the agency’s own cryptologists treating interstellar messages as a legitimate intellectual exercise. It drew a direct response. In the next issue, NSA mathematician Howard Campaigne published a second set of puzzle messages, and he printed the key in 1969. Both pieces are covered on the Campaigne page. The later Wow! signal of 1977 (covered here) came from the kind of hydrogen-line search that Callimahos describes.
Status
A published, unclassified professional article. It makes no claim about any real contact or sighting. NSA released it before its 2025 transfer to the National Archives.
Sources
- National Archives catalog entry: https://catalog.archives.gov/id/596347893
- PDF of the record: https://catalog.archives.gov/medialz/electronic-records/rg-615/580103959/457UAP00004_released.pdf
- Series: Records from the National Security Agency Relating to Unidentified Anomalous Phenomena: https://catalog.archives.gov/id/580103959
- National Archives, Record Group 615 UAP records: https://www.archives.gov/research/topics/uaps/rg-615