Choudhuri, Arka Rai, and Subhamoy Maitra. 2017. “Significantly Improved Multi-Bit Differentials for Reduced Round Salsa and ChaCha”. IACR Transactions on Symmetric Cryptology 2016 (2): 261-87. https://doi.org/10.13154/tosc.v2016.i2.261-287.