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 (2122.61, 2123.48, 2119.94), (2122.99, 2154.83, 2159.94), and (2123.53, 2238.13, 2239.95) for ARIA- 128, ARIA-192, and ARIA-256, respectively.