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Paper 2007/158

A Simple Security Analysis of Hash-CBC and a New Efficient One-Key Online Cipher

Mridul Nandi

Abstract

In Crypto 2001, Bellare {\em et al.} introduced {\em online cipher} (or online permutation) and proposed two Hash-CBC mode constructions, namely {\bf HCBC} and {\bf HPCBC} along with security proofs. We observe that, the security proofs in their paper are {\em wrong} and it may not be fixed easily. In this paper, we provide a {\em simple} security analysis of these online ciphers. Moreover, we propose two variants of HPCBC, namely {\bf MHCBC-1} and {\bf MHCBC-2}. The first variant, MHCBC-1, is a slight modification of HPCBC so that it is more efficient in performance as well as in memory compare to HPCBC. The other one, MHCBC-2 requires only {\em one-key} (note that, HCBC and HPCBC require at least two and three keys respectively) and does not require any $\varepsilon$-$\mathrm{\Delta}$Universal Hash Family (which is costly in general).

Metadata
Available format(s)
PDF PS
Category
Secret-key cryptography
Publication info
Published elsewhere. Unknown where it was published
Keywords
random permutationpseudo random permutationOnline functionOnline permutationHash-CBC.
Contact author(s)
mridul nandi @ gmail com
History
2007-05-07: revised
2007-05-07: received
See all versions
Short URL
https://ia.cr/2007/158
License
Creative Commons Attribution
CC BY
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