Differential-Linear Attacks Against the Stream Cipher Phelix

The previous key recovery attacks against Helix obtain the key with about 288 operations using chosen nonces (reusing nonce) and about 1000 adaptively chosen plaintext words (or 235.6 chosen plaintext words). The stream cipher Phelix is the strengthened version of Helix. In this paper we apply the differential-linear cryptanalysis to recover the key of Phelix. With 234 chosen nonces and 237 chosen plaintext words, the key of Phelix can be recovered with about 241.5 operations.