You can't legally get around copyright with technicalities, because any bit string can be derived from any other bit string by a sequence of one bit edits, and according to the legal doctrine, if we start with a copyrighted work, each such edit is creates a derived work.

You can disguise borrowed code such that, in the first place, nobody will suspect that it's derived from anything, and even then, they won't have evidence that it's derived.

Changing a few names and superficial organization details, on a large and significant work, will likely not fool anyone.

If it's a small module or just one function, quite probably easily so. You don't even have to understand how the code works; if you just know the paper from where the original author got the code, you can just say you implemented the detailed requirements there and validated it on the available test vectors.