Revisiting the IDEA philosophy
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This paper presents an implementation of the IDEA block cipher
encrypting at 5.4 clock cycles / byte in counter mode on an Intel
Core2 processor, as well as the design of a new compression function,
named WIDEA, able to process data at a rate of 6.0 clock cycles / byte
on the same CPU.
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Bibliographical References
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Pascal Junod
and Marco Macchetti,
"Revisiting the IDEA philosophy", Fast Software
Encryption, 16th International Workshop, FSE 2009,
February 22-25, 2009, Leuven,
Belgium, Revised Selected Papers, Lecture Notes in
Computer Science, 5665, pp. 277-295, Springer,
2009. |
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Abstract
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Since almost two decades, the block cipher IDEA has resisted an exceptional
number of cryptanalysis attempts. At the time of writing, the best published
attack works against 6 out of the 8.5 rounds (in the non-related-key attacks
model), employs almost the whole codebook,
and improves the complexity of an exhaustive key search by a factor of only
two. In a parallel way, Lipmaa demonstrated that IDEA can
benefit from SIMD (Single Instruction, Multiple Data) instructions on
high-end CPUs, resulting in very fast implementations. The aim of this paper
is two-fold: first, we describe a parallel, time-constant implementation of
eight instances of IDEA able to encrypt in counter mode at a speed of
5.42 cycles/byte on an Intel Core2 processor. This is comparable
to the fastest stream ciphers and notably faster than the best known
implementations of most block ciphers on the same processor. Second, we
propose the design of a
new block cipher, named WIDEA, leveraging
on IDEA's outstanding security-performance ratio. We furthermore propose a new
key-schedule algorithm in replacement of completely linear IDEA's one, and we
show that it is
possible to build a compression function able to process data at a speed of
5.98 cycles/byte. A significant property of WIDEA is that it closely
follows the security rationales defined by Lai and Massey in 1990, hence
inheriting all the cryptanalysis done the past 15 years in a very natural way.
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Download
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Paper
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Talk given at FSE'09, February 24th, Leuven, Belgium, 2009
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Last updated January 14th, 2010
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