I'm working on an old CTF challenge where AES-128 was used on a 16 byte block. I have the round 10 key and the ciphertext. What techniques exist for obtaining the plaintext?

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    $\begingroup$ hint: search for AES master key Round Keys $\endgroup$ – kelalaka Nov 10 '18 at 18:04

Since this is CTF, I'll give you some detailed hints.

  • Normally by using only a ciphertext, you cannot determine the plaintext, since for every key the deciphered ciphertext is a valid plaintext and some of them are perfect in English or any other language. So, some other information must be given to you for verification.
  • 16-Byte just means one block for AES.
  • There is a difference in key schedules between AES-128 and AES-182,AES-256.
  • Your CTF is not possible with the key schedules of AES-192 and AES-256
  • You have given only, one round key. The different key schedule of AES -128 will enable this.
  • Search for AES master key Round Keys ( in this site)

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