Is the linear and differential cryptanalysis only dependent on Sbox? While performing the linear and differential cryptanalysis a Linear Approximation Table(LAT) and a Different Distribution Table(DDT) is required which is created exploiting the S-box of the cipher which can be found in the tutorial of Howard heys. Now my question is if I take a random S-box for every other encryption and my cipher has a very good diffusion mechanism is my cipher still vulnerable to linear and differential attacks?
The question is contradicting with the title.
A random S-Box with a &quot;very good diffusion mechanism&quot; would be perfectly ok, assuming enough rounds.
A random S-Box without a &quot;very good diffusion mechanism&quot; would be worse.
For example, consider the AES with the S-Box replaced by a random S-Box. We can use known bounds on the number of active S-Boxes in AES (even the simple one - 5 active S-Boxes every two rounds), and use the differential uniformity / nonlinearity of the new random S-Box to give a provable bound on the differential/linear cryptanalysis. Possibly, we would need to increase the number of rounds a bit. Though, such proof would refer only to a single-trail cryptanalysis, but this is exactly what was done for AES. For example, truncated or higher-order differential cryptanalysis would not be covered.
Answering your question: security against linear/differential cryptanalysis depends both on the S-Box and the linear layer, though in a different way. Of course, in an edge case like fully linear S-Box, a strong linear layer won't help.