Moving a Step of ChaCha in Syncopated Rhythm

ePrint Report: Moving a Step of ChaCha in Syncopated Rhythm

Shichang Wang, Meicheng Liu, Shiqi Hou, Dongdai Lin

The stream cipher ChaCha is one of the most widely used ciphers in the real world, such as in TLS, SSH and so on. In this paper, we study the security of ChaCha via differential cryptanalysis based on probabilistic neutrality bits (PNBs). We introduce the \textit{syncopation} technique for the PNB-based approximation in the backward direction, which significantly amplifies its correlation by utilizing …

cipher ciphers eprint report moving report security ssh stream stream cipher study tls world