Someone is able to explain in detail the construction and operation of the DES S-Box, which from n input bits input, produces an output of m bits, with m <n?
How can I get these properties?
The process is reversible? How can I get the initial bits from those produced by the S-Box?
Thanks in advance for your answers.
Everybody speaks of the whole algorithm, but I need to know the process that allows to obtain an output, smaller than the input, which is reversible. I can't understand how it's possible.
Please, help me.