Luby-Racko Backwards: Increasing Security by Making Block Ciphers Non-Invertible (0)
| Venue: | Advances in Cryptology|EUROCRYPT '98 Proceedings |
| Citations: | 5 - 2 self |
BibTeX
@INPROCEEDINGS{Bellare_luby-rackobackwards:,
author = {Mihir Bellare and Ted Krovetz},
title = {Luby-Racko Backwards: Increasing Security by Making Block Ciphers Non-Invertible},
booktitle = {Advances in Cryptology|EUROCRYPT '98 Proceedings},
year = {},
publisher = {Springer-Verlag}
}
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Abstract
We argue that the invertibility of a block cipher can reduce the security of schemes that use it, and a better starting point for scheme design is the non-invertible analog of a block cipher, that is, a pseudorandom function #PRF#. Since a block cipher may be viewed as a pseudorandom permutation, we are led to investigate the reverse of the problem studied by Luby and Racko#, and ask: #how can one transform a PRP into a PRF in as security-preserving a way as possible?" The solution we propose is data-dependent re-keying. As an illustrative special case, let E : f0; 1g n #f0; 1g n !f0; 1g n be the block cipher. Then we can construct the PRF F from the PRP E by setting F #k; x#=E#E#k;x#;x#. We generalize this to allow for arbitrary block and key lengths, and to improve e#ciency. We prove strong quantitative bounds on the value of data-dependent re-keying in the Shannon model of an ideal cipher, and take some initial steps towards an analysis in the standard model. Keywords: Birthday attacks, block ciphers, pseudorandom functions, symmetric encryption. # Dept. of Computer Science & Engineering, Mail Code 0114, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. E-mail: mihir@cs.ucsd.edu. Web page: http:##www-cse.ucsd.edu#users#mihir. Supported in part by NSF CAREER Award CCR-9624439 and a 1996 Packard Foundation Fellowship in Science and Engineering. y Dept. of Computer Science, Engineering II Bldg., UniversityofCalifornia at Davis, Davis, CA 95616, USA. E-mail: fkrovetz,rogawayg@cs.ucdavis.edu. Web page: http:##www.cs.ucdavis.edu#~fkrovetz,rogawayg. Supported in part by NSF CAREER Award CCR-9624560 and a MICRO grant from RSA Data Security, Inc. Contents 1
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