OCB是由Phillip Rogaway教授等人设计的一种认证加密模式。到目前为止它已有三个版本:OCB1(2001年)、OCB2(2003年)和 OCB3(2011年)。其中,OCB1 是IEEE 802.11i 的可选工作模式之一(也叫WRAP);OCB2 是ISO/IEC 19772:2009提及的标准之一。有鉴于此,关于OCB的文章比较多,需注意区别。按照OCB主页上的说法,OCB的主要文章是以下几个:
- The original OCB paper. The proceedings version is in ACM CCS (2001) and the journal version is in ACM TISSEC (2003).
- A paper about dealing with associated data. Appears in ACM CCS (2002).
- A paper to develop the message authentication code, PMAC, that shaped the way AUTH is computed in OCB. Appears in EUROCRYPT (2002).
- A paper about efficiently realizing tweakable blockciphers, and about using tweakable blockcipher to improve OCB. Appears in ASIACRYPT (2004).
- Finally, a timing study about AE modes, along with refinements to get to the final version of OCB. Appears at FSE 2011.
LibTomCrypt中的OCB模式是实现了OCB1,参见文章OCB: A Block-Cipher Mode of Operation for Efficient Authenticated Encryption。OCB各版本差别比较大,且OCB1存在某些设计上的不足。
Mode OCB1 had a defect that practitioners were quick to point out: it had not been designed to natively handle associated-data (AD). Associated-data refers to stuff, say a message header, that needs to be authenticated but should not encrypted.
所以在这里不再介绍LibTomCrypt中的OCB模式。
参考文献
- OCB主页 OCB - An Authenticated-Encryption Scheme - Rogaway
- OCB相关问题 OCB - An Authenticated-Encryption Scheme - Background - Rogaway
- 维基百科OCB http://en.wikipedia.org/wiki/OCB_mode
- P. Rogaway, M. Bellare, and J. Black. OCB: A block-cipher mode of operation for efficient authenticated encryption. ACM Transactions on Information and System Security, vol. 6, no. 3, pp. 365–403, 2003. Earlier version, with T. Krovetz, in CCS 2001.