I am currently in the process of learning how AES actually works and that works great as of now but when it comes to the Rijndael's key schedule I have a question. From what I have read, I have to make a expanded key that is 240 bytes in size to supply enough subkeys to the whole process of a AES encryption using a 256 bit key. Does this mean that I need to make the expanded key exactly 240 bytes or can I make it 256 bytes and discard the last 16 bytes? I ask this because from what I understand, each round of the key expansion gives me 32 bytes of round keys. In that case I have to do 8 rounds of key expansion to supply the encryption with enough subkeys since 7 rounds will only give me 224 bytes.

  • $\begingroup$ Possible duplicate crypto.stackexchange.com/questions/2486/… $\endgroup$ – kodlu May 29 '17 at 21:41
  • $\begingroup$ The question you linked, does not exist. $\endgroup$ – mat May 29 '17 at 22:11
  • $\begingroup$ Eh, did the community ♦ just turn a double pasted URL into a single URL without intervention? Should I join the resistance already? $\endgroup$ – Maarten Bodewes May 30 '17 at 0:45