I am trying to understand how differential Cryptanalysis works. Here I read how to use differential cryptoanalysis for cracking FEAL4 cipher.
The big gotcha with this process is that you cannot just reuse the above differential path to crack rounds 2 and 3. You must build new differential characteristics that only cover the uncracked rounds.
As I understood you cannot use the same differential for cracking all keys. For each round key, you need to use new differential. Could you explain why?