Miyaji Laboratory

Stream ciphers, which are often used for secure communications, are one of common key ciphers. Salsa20 is a stream cipher designed by D.J.Bernstein in 2005, and research on its security is highly necessary in ensuring information security. Key recovery attack by differential cryptanalysis is effective as one of the attack methods applied to Salsa20. Differential cryptanalysis is a method of discovering the non- randomness of cryptographic algorithms by tracing how input differences affect output differences. Also, linear cryptanalysis combined with differential cryptanalysis has been frequently performed. Therefore, in this research, in order to improve the existing linear differential decoding for Salsa20, we proposed a new combination of input and output differentials based on the linear formula, and showed the result of the attack experiment with bias.