I was trying to decrypt a text encrypted with AES and ECB mode.
I did try several key and IV. I solved it by ignoring IV. (The IV was given, but it was maybe a distractor)
My question is in which cases IV is needed and in which is not?
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A quick list from Wikipedia;
There is a mode of AES that can survive without an IV under certain assumptions.
In particular, the XEX form of AES is designed to function in the absence of a working IV and in particular survives IV reuse. There's one downside in that if you do something like write enough data to the same block and an attacker can see all of the states the security collapses, but it's good it what it's designed for.