Offset codebook mode (OCB mode) is an authenticated encryption mode of operation for cryptographic block ciphers.[1][2] OCB mode was designed by Phillip Rogaway, who credits Mihir Bellare, John Black, and Ted Krovetz with assistance and comments on the designs. It is based on the integrity-aware parallelizeable mode (IAPM) of authenticated encryption by Charanjit S. Jutla. The OCB2 version was proven insecure, while the original OCB1 as well as OCB3 from 2011 are still considered secure.