Improved Linear Cryptanalysis of Round-Reduced ARIA

Abstract

ARIA is an iterated SPN block cipher developed by a group of Korean cryptographers in 2003, established as a Korean standard in 2004 and added to the Transport Layer Security (TLS) supported cipher suites in 2011. It encrypts 128-bit blocks with either 128, 192, or 256-bit key. In this paper, we revisit the security of round-reduced ARIA against linear cryptanalysis and present a 5-round linear hull using the correlation matrix approach to launch the first 8-round key recovery attack on ARIA-128 and improve the 9 and 11-round attacks on ARIA-192/256, respectively, by including the post whitening key. Furthermore, sin all our attacks, we manage to recover the secret master key. The (data in known plaintexts, time in round-reduced encryption operations, memory in 128-bit blocks) complexities of our attacks are ($2^{122.61}$, $2^{123.48}$, $2^{119.94}$), ($2^{122.99}$, $2^{154.83}$, $2^{159.94}$), and ($2^{123.53}$, $2^{238.13}$, $2^{239.95}$) for ARIA-128, ARIA-192, and ARIA-256, respectively.