New Results on Boomerang and Rectangle Attacks

The boomerang attack is a new and very powerful cryptanalytic technique. However, due to the adaptive chosen plaintext and ciphertext nature of the attack, boomerang key recovery attacks that retrieve key material on both sides of the boomerang distinguisher are hard to mount. We also present a method for using a boomerang distinguisher, which enables retrieving subkey bits on both sides of the boomerang distinguisher. The rectangle attack evolved from the boomerang attack.In this paper we present a new algorithm which improves the results of the rectangle attack. Using these improvements we can attack 3.5-round SC2000 with 2 adaptive chosen plaintexts and ciphertexts, and 10-round Serpent with time complexity of 2 memory accesses (which are equivalent to 2 Serpent encryptions) with data complexity of 2 chosen plaintexts.