**A General Construction of Tweakable Block Ciphers and Different Modes of Operations**

*Debrup Chakraborty and Palash Sarkar*

**Abstract: **This work builds on earlier work by Rogaway at Asiacrypt 2004 on
tweakable block cipher (TBC) and modes of operations. Our first
contribution is to generalize Rogaway's TBC construction by working
over a ring {\ring} and by the use of a masking sequence of
functions. The ring {\ring} can be instantiated as either $GF(2^n)$
or as $\bbbz_{2^n}$. Further, over $GF(2^n)$, efficient
instantiations of the masking sequence of functions can be done
using either a binary Linear Feedback Shift Register (LFSR); a powering
construction; a cellular automata map; or by using a word oriented LFSR.
Rogaway's TBC construction
was built from the powering construction over $GF(2^n)$. Our second
contribution is to use the general TBC construction to instantiate
constructions of various modes of operations including authenticated
encryption (AE) and message authentication code (MAC). In particular,
this gives rise to a family of efficient one-pass AE mode of operation.
Out of these, the mode of operation obtained by the use of word oriented
LFSR promises to provide a masking method which is more efficient than the
one used in the well known AE protocol called OCB.

**Category / Keywords: **secret-key cryptography / tweakable block cipher, modes of operations, AE, MAC, AEAD.

**Publication Info: **An abridged version of this paper has appeared in the proceedings of Inscrypt 2006.

**Date: **received 27 Jan 2007, last revised 26 Jul 2007

**Contact author: **palash at isical ac in

**Available format(s): **PDF | BibTeX Citation

**Note: **Subsequent to the previous version, we realised that word oriented LFSRs can be used to generate the masks.

**Version: **20070726:113236 (All versions of this report)

**Short URL: **ia.cr/2007/029

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