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Improved meet-in-the-middle attacks on 7 and 8-round ARIA-192 and ARIA-256
Akshima, D. Chang, M. Ghosh, A. Goel,
Published in Springer Verlag
Volume: 9462
Pages: 198 - 217
The ARIA block cipher has been established as a Korean encryption standard by Korean government since 2004. In this work, we re-evaluate the security bound of reduced round ARIA-192 and ARIA- 256 against meet-in-the-middle (MITM) key recovery attacks in the single key model. We present a new 4-round distinguisher to demonstrate the best 7 & 8 round MITM attacks on ARIA-192/256. Our 7-round attack on ARIA-192 has data, time and memory complexity of 2113, 2135.1 and 2130 respectively. For our 7-round attack on ARIA-256, the data/time/memory complexities are 2115, 2136.1 and 2130 respectively. These attacks improve upon the previous best MITM attack on the same in all the three dimensions. Our 8-round attack on ARIA-256 requires 2113 cipher calls and has time and memory complexity of 2245.9 and 2138 respectively. This improves upon the previous best MITM attack on ARIA-256 in terms of time as well as memory complexity. Further, in our attacks, we are able to recover the actual secret key unlike the previous cryptanalytic attacks existing on ARIA-192/256. To the best of our knowledge, this is the first actual key recovery attack on ARIA so far. We apply multiset attack - a variant of meet-in-the-middle attack to achieve these results. © Springer International Publishing Switzerland 2015.