A compress slide attack on the full GOST block cipher

• Introducing a novel variant of the slide attack, called compress slide attack.
• Constructing a consecutive slid sequence for the GOST block cipher.
• Presenting a compress slide attack on the full 32-round GOST block cipher.

Slide attacks are powerful tools that analyze iterated block ciphers with an arbitrarily large number of rounds by exploiting their self-similarity. But conventional techniques fail if there are unslid rounds in the middle of a slid sequence. This paper introduces a novel variant of the slide attack, called the compress slide attack. This technique compresses several unslid rounds with a high probability in order to break ciphers with unslid rounds in the middle of a slid sequence. In particular, a compress slide attack on the full 32-round GOST block cipher is presented. It can recover a key with a time complexity of about 2192 encryptions and 264 data.