Related-Key Differential Slide Attack Against Fountain V1
The stream cipher FOUNTAIN was introduced in April 2019 as one of the candidates in the NIST lightweight crypto standardization process. In this paper we introduce a slide attack that leads to the construction of 32 relations on key bits, with time complexity around $17\times 2^{80}$. The success of the attack is around 98%. We also present some properties of the internal state transitions that allow the identification of (key-iv-ad) input data that produce identical ciphertexts, with probability of $2^{-32}$.