Military Cryptanalytics, Part III

The NSA has just declassified and released a redacted version of Military Cryptanalytics, Part III, by Lambros D. Callimahos, October 1977.

Parts I and II, by Lambros D. Callimahos and William F. Friedman, were released decades ago—I believe repeatedly, in increasingly unredacted form—and published by the late Wayne Griswold Barker’s Agean Park Press. I own them in hardcover.

Like Parts I and II, Part III is primarily concerned with pre-computer ciphers. At this point, the document only has historical interest. If there is any lesson for today, it’s that modern cryptanalysis is possible primarily because people make mistakes

The monograph took a while to become public. The cover page says that the initial FOIA request was made in July 2012: eight and a half years ago.

And there’s more books to come. Page 1 starts off:

This text constitutes the third of six basic texts on the science of cryptanalytics. The first two texts together have covered most of the necessary fundamentals of cryptanalytics; this and the remaining three texts will be devoted to more specialized and more advanced aspects of the science.

Presumably, volumes IV, V, and VI are still hidden inside the classified libraries of the NSA.

And from page ii:

Chapters IV-XI are revisions of seven of my monographs in the NSA Technical Literature Series, viz: Monograph No. 19, “The Cryptanalysis of Ciphertext and Plaintext Autokey Systems”; Monograph No. 20, “The Analysis of Systems Employing Long or Continuous Keys”; Monograph No. 21, “The Analysis of Cylindrical Cipher Devices and Strip Cipher Systems”; Monograph No. 22, “The Analysis of Systems Employing Geared Disk Cryptomechanisms”; Monograph No.23, “Fundamentals of Key Analysis”; Monograph No. 15, “An Introduction to Teleprinter Key Analysis”; and Monograph No. 18, “Ars Conjectandi: The Fundamentals of Cryptodiagnosis.”

This points to a whole series of still-classified monographs whose titles we do not even know.

EDITED TO ADD: I have been informed by a reliable source that Parts 4 through 6 were never completed. There may be fragments and notes, but no finished works.

Posted on January 4, 2021 at 2:34 PM6 Comments


Friedwoman January 5, 2021 3:45 AM

There’s another recent book about pre-computer ciphers: “Codebreaking: A Practical Guide” by Elonka Dunin and Klaus Schmeh. Contrary to “Military Cryptanalytics”, it is new and includes computer-based methods for breaking old ciphers.

Clive Robinson January 5, 2021 5:21 AM

@ Bruce,

“The monograph a while to become public.”

Appears to be missing “took” or similar word.

Goat January 5, 2021 9:07 AM

@Clive +1
Just do a git revert, this would save a lot of effort for the people commening on this blog

David Rudling January 5, 2021 10:00 AM


Sorry. I just realised that version to which I posted a link earlier (still stuck in moderation as I write this) is William Friedman’s earlier Army (not NSA) version.

Clive Robinson January 8, 2021 5:25 AM

@ internet individual,

The book on code-breaking website isnt for sale in the US according to Amazon.

There has always been issues with getting books published outside of the US sold in the US, it’s in part to do with US legislation on copyright.

So a quick look in the “dead tree cave” that I have suggests you might want to start with,

CRYPTANALYSIS : a study of ciphers and their solutions.

(formerly published under the title “Elementary Cryptanalysis”).

By Helen Fouché Gainess, Dover Publications Inc New York.

ISBN 978-0-486-20097-2

It was originally written in 1939, so covers “hand ciphers” and though teenagers can read it and do the examples it is actually a professional introduction to cryptanalysis.

I purchased a new copy a few years back as a replacment to one that had been borrowed but not returned. It cost £6.99 from Foyles in London. Amazon UK wants only £8.09 new and ondicates 4.50 for second hand.

There are also PDF’s you can find on the Internet by just searching on the authors name, though how good bad they are I don’t know.

Speaking of PDFs a number of US military training guides for WWII cryptographers are available.

David Rudling January 12, 2021 2:54 PM

Clive Robinson is, as usual, quite correct about the availability of WWII guides.

William Friedman did complete parts I – IV of Military Cryptanalysis for the Army and they are available here:-

ht tps://

but it seems only parts I – III were updated for a later NSA version.

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