Security News > 2021 > May > Newly Declassified NSA Document on Cryptography in the 1970s
From the dates and the title, the George Davida patent application which NSA unsuccesfully tried to block would have been US4202051A, for a key stream generator based on a LFSR combined with a non-linear feedback circuit.
"In April 1978 a patent application made by Carl Nicolai for a speech scrambling device was evaluated by the NSA using Inman's new criteria. Once again, there was disagreement between NSA directorates. Neither Research and Engineering nor COMSEC believed that Nicolai's invention should be classified. Howard Rosenblum, DDC, noted that Nicolai employed"a sophisticated use of well-known, open-source techniques" of spread spectrum technology and that "so many unclassified spread spectrum systems are already in the public domain that it is too late to try to close the door by imposing secrecy orders based solely on the fact that the system uses spread spectrum techniques.
Inman decided to "err on the side of national security," as he explained it, and he requested a secrecy order on the Nicolai patent.
The following notice amends the notice published in the Official Gazette of May 13, 1975 to extend the royalty free immunity under foreign patents to apparatus manufactured outside of the United States and sold for use or used within the United States and to extend certain dates until March 1, 1977.
Such license extends throughout the US and includes a royalty free immunity from suit, with respect to apparatus which employs the published data encryption information or complies with the standard(s) and is manufactured in the USA, or is manufactured outside of the USA and is sold for use or used within the USA, under any and all foreign patents now or hereafter assigned to IBM, the infringement of which could not be avoided by any apparatus which can be canstructed and operated for the purpose of employing the published data encryption information or complying with the standard(s).
US3798359 together with US3796830 had effective foreign coverage in at least BE, DE, NL, FR, GB, IT, JP, and SE. The Philips patent department certainly had a lot of competent practitioners in its employ, and must have considered the PX-1000 like a grenade with the pin off.