Cryptology ePrint Archive: Report 2017/841

Efficient Length Doubling From Tweakable Block Ciphers

Yu Long Chen and Atul Luykx and Bart Mennink and Bart Preneel

Abstract: We present a length doubler, LDT, that turns an n-bit tweakable block cipher into an efficient and secure cipher that can encrypt any bit string of length [n..2n-1]. The LDT mode is simple, uses only two cryptographic primitive calls (while prior work needs at least four), and is a strong length-preserving pseudorandom permutation if the underlying tweakable block ciphers are strong tweakable pseudorandom permutations. We demonstrate that LDT can be used to neatly turn an authenticated encryption scheme for integral data into a mode for arbitrary-length data.

Category / Keywords: secret-key cryptography / length doubler, LDT, tweakable block ciphers, authenticated encryption

Original Publication (with minor differences): IACR-FSE-2018

Date: received 1 Sep 2017

Contact author: yulong chen at student kuleuven be; Atul Luykx@esat kuleuven be; b mennink@cs ru nl; Bart Preneel@esat kuleuven be

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Version: 20170906:181228 (All versions of this report)

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