Handbook of Applied Cryptography gives two resources for the OFB mode

  1. 1980 FIPS 81. This doesn't give any references, unlike NIST.
  2. 1983 ANSI X3.106, unfortunately pay-walled.

Who is the inventor of the OFB mode of operation?

  • 2
    $\begingroup$ An interesting downvote. Reference requests are valid questions on crytography.se $\endgroup$
    – kelalaka
    Jan 28 at 12:21

1 Answer 1


It's difficult to be sure of the attribution here, but my best guess would be Carl M. Campbell Jr., from the (later renamed to Mastercard) Interbank Card Association.

Soon after the DES was standardized, NBS (now known as NIST) held a conference on "Computer Security and the Data Encryption Standard" in February 1977, whose proceedings are still available. Among the topics presented in this conference, various modes of operation were suggested:

  • Barrie Morgan from Dakotek Inc. suggested the ciphertext feedback mode (page 38);
  • Carl M. Campbell Jr. proposed the output feedback (called internal feedback in the paper), ciphertext feedback, and infinite garbled extension modes (page 54 and a later separate paper).

Those modes, along with CBC (invented by the IBM DES team), later ended up in FIPS 81. It's difficult to attribute the invention to Campbell, however; it may well be the case that these modes were already the established practice within the companies attempting to use the DES to encrypt data.


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