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3

Actually, there's no known way (assuming practical amounts of computing power) to distinguish keying methods 1 and 2. You mention a "brute-force attack of complexity $O(2^{56})$ followed by a chosen plaintext attack of complexity $O(2^{57})$", there's no obvious way to frame an attack against either of the first two options in this matter; you can't do a ...

2

Your Formulas are alright, but there is some additional information from the exercise/setup: The exercise states, that $F$ should be considered as a blackbox (otherwise you could use the internal stages of $F$, as poncho already suggested). However, as I understand it you can stil evaluate $F$ on any input of your choice. At this point, you can do a couple ...

1

After base64 decoding we get (hex) "5d f8 be 87 82 2b ea 5e f3 5c 23 fe 37 81 0f bd" which has a size of two blocks. Of your small wordlist, only marketing has so many letters that it needs two blocks: "m a r k e t i n" as the first, "g 07 07 07 07 07 07 07" as the second (or another padding, but this is a common one), and so can correspond to this ...

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