offering similar functionality requires twice as many block cipher operations per message block (associated data requires one, as in OCB).

Patents

While OCB is now public domain, Rogaway initially patented OCB mode so that he could charge for commercial licenses and in attempt to stop his work showing up in military-related projects. Rogaway intentionally abandoned his OCB patents in 2021.

Two U.S. patents were issued for OCB mode. The patents have hindered approval by the National Institute of Standards and Technology.

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