Paper 2007/109 Original: eprint.iacr.org/2007/109 ↗
How to Enrich the Message Space of a Cipher
Abstract
Given (deterministic) ciphers $\calE$ and~$E$ that can encipher messages of $\el$ and $n$ bits, respectively, we construct a cipher~$\calE^*=XLS[\calE,E]$ that can encipher messages of $\el+s$ bits for any $s<n$. Enciphering such a string will take one call to~$\calE$ and two calls to~$E$. We prove that~$\calE^*$ is a strong pseudorandom permutation as long as~$\calE$ and~$E$ are. Our construction works even in the tweakable and VIL (variable-input-length) settings. It makes use of a multipermutation (a pair of orthogonal Latin squares), a combinatorial object not previously used to get a provable-security result.
Metadata
- Available format(s)
PDF- Category
- Secret-key cryptography
- Publication info
- Preprint.
- History
- 2015-02-27: last updated
- 2007-03-26: published
- Short URL
- https://ia.cr/2007/109
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2007/109,
author = {Thomas Ristenpart and Phillip Rogaway},
title = {How to Enrich the Message Space of a Cipher},
howpublished = {Cryptology {ePrint} Archive, Paper 2007/109},
year = {2007},
url = {https://eprint.iacr.org/2007/109}
}