The GOST block cipher is the Russian encryption standard published in 1989. In spite of considerable cryptanalytic efforts over the past 20 years, a key recovery attack on the full GOST block cipher without any key conditions (e.g., weak keys and related keys) has not been published yet. In this paper, we show a first single-key attack, which works for all key classes, on the full GOST block cipher. To construct the attack, we develop a new attack framework called Reflection-Meet-inthe-Middle Attack. This approach combines techniques of the reflection attack and the meet-in-the-middle attack. We apply it to the GOST block cipher with further novel techniques which are the effective MITM techniques using equivalent keys on short rounds. As a result, a key can be recovered with 2225 computations and 232 known plaintexts.
['Takanori Isobe']
A single-key attack on the full GOST block cipher