I am currently looking into how AES works and found a calculator online: http://testprotect.com/appendix/AEScalc

I understand that the AES process has 10 rounds of calculations. Does this mean that this calculator only provides the cipher text for round 0? Would I need to copy the output cipher text and manually paste it into the input of the calculator and encrypt it with the same key 10 times?

Thanks for any assistance. I’m fairly new to the process of AES.

  • 3
    $\begingroup$ AES-128 has 10 rounds. AES-192 12 and AES-256 has 14 rounds. If you want to learn the steps use cryptool AES step by step and see the stick figure guide to AES and then read the AES book $\endgroup$
    – kelalaka
    Jun 12 at 18:56
  • 2
    $\begingroup$ The website you link to does AES-128 (that is, it expects a key of 128/8=16 bytes). It does all the 10 rounds (including the last special one and the 11th AddRoundKey), and does not show intermediary results. $\endgroup$
    – fgrieu
    Jun 12 at 19:01

Unless mentioned specifically you should assume that AES calculators will perform all the calculations necessary to implement the block cipher.

Beware that sometimes these calculators also use a mode of operation and a padding mode, often without mentioning it. They may also provide encodings without mentioning it.

Personally I distrust most online calculators for these reasons. I would rather use Java to be able to configure everything as required, or use tools such as OpenSSL command line (with the explicit -K and -iv parameters).

The one you show performs all the 10 required rounds for AES. It doesn't use any mode of operation (such as ECB or CBC) or related padding mechanism. It is rather sensible as it uses hexadecimal encoding for all values (key, input and output) and mentions it explicitly as well.

For a single round result you can use the crypttool which kelaka pointed out in the comments section. Please make sure that you select one round and disable "chaining". It would be tricky to explain the other options without explaining AES itself; I would suggest to read into AES and only use the options after they have been explained to you.


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