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OCB: a block-cipher mode of operation for efficient authenticated encryption

By Phillip Rogaway, Mihir Bellare and John Black

Abstract

We describe a parallelizable block-cipher mode of operation that simultaneously provides privacy and authenticity. OCB encrypts-and-authenticates a nonempty string M ∈{0, 1} ∗ using ⌈|M|/n ⌉ + 2 block-cipher invocations, where n is the block length of the underlying block cipher. Additional overhead is small. OCB refines a scheme, IAPM, suggested by Charanjit Jutla. Desirable properties of OCB include the ability to encrypt a bit string of arbitrary length into a ciphertext of minimal length, cheap offset calculations, cheap key setup, a single underlying cryptographic key, no extended-precision addition, a nearly optimal number of block-cipher calls, and no requirement for a random IV. We prove OCB secure, quantifying the adversary’s ability to violate the mode’s privacy or authenticity in terms of the quality of its block cipher as a pseudorandom permutation (PRP) or as a strong PRP, respectively

Topics: Categories and Subject Descriptors, E.3 [Data Encryption, Standards General Terms, Security, Performance, Theory Additional Key Words and Phrases, AES, authenticity, block-cipher usage, cryptography, encryption, integrity, modes of operation, provable security, standards
Year: 2003
OAI identifier: oai:CiteSeerX.psu:10.1.1.135.9030
Provided by: CiteSeerX
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