Cryptology ePrint Archive: Report 2014/157

CLOC: Authenticated Encryption for Short Input

Tetsu Iwata and Kazuhiko Minematsu and Jian Guo and Sumio Morioka

Abstract: We define and analyze the security of a blockcipher mode of operation, CLOC, for provably secure authenticated encryption with associated data. The design of CLOC aims at optimizing previous schemes, CCM, EAX, and EAX-prime, in terms of the implementation overhead beyond the blockcipher, the precomputation complexity, and the memory requirement. With these features, CLOC is suitable for handling short input data, say 16 bytes, without needing precomputation nor large memory. This property is especially beneficial to small microprocessors, where the word size is typically 8 bits or 16 bits, and there are significant restrictions in the size and the number of registers. CLOC uses a variant of CFB mode in its encryption part and a variant of CBC MAC in the authentication part. We introduce various design techniques in order to achieve the above mentioned design goals. We prove CLOC secure, in a reduction-based provable security paradigm, under the assumption that the blockcipher is a pseudorandom permutation. We also present our preliminary implementation results.

Category / Keywords: secret-key cryptography / CLOC, blockcipher, authenticated encryption with associated data, security analysis, efficiency analysis.

Original Publication (with major differences): IACR-FSE-2014

Date: received 28 Feb 2014

Contact author: iwata at cse nagoya-u ac jp

Available format(s): PDF | BibTeX Citation

Note: A preliminary version of this paper appears in the pre-proceedings of FSE 2014. This is the full version.

Version: 20140301:161713 (All versions of this report)

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