International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 24 July 2015

Hwajeong Seo, Zhe Liu, Jongseok Choi, Taehwan Park, and Howon Kim
ePrint Report ePrint Report
In WISA\'13, a novel lightweight block cipher named LEA

was released. This algorithm has certain useful features for hardware

and software implementations, i.e., simple ARX operations, non-S-box

architecture, and 32-bit word size. These features are realized in several

platforms for practical usage with high performance and low overheads.

In this paper, we further improve 128-, 192- and 256-bit LEA encryption

for low-end embedded processors. Firstly we present speed optimization

methods. The methods split a 32-bit word operation into four byte-wise

operations and avoid several rotation operations by taking advantages of

efficient byte-wise rotations. Secondly we reduce the code size to ensure

minimum code size.We nd the minimum inner loops and optimize them

in an instruction set level. After then we construct the whole algorithm

in a partly unrolled fashion with reasonable speed. Finally, we achieved

the fastest LEA implementations, which improves performance by 10.9%

than previous best known results. For size optimization, our implemen-

tation only occupies the 280B to conduct LEA encryption. After scaling,

our implementation achieved the smallest ARX implementations so far,

compared with other state-of-art ARX block ciphers such as SPECK and

SIMON.

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