Like said, you want some difficulty, try to find the function. There is a tuto about how to find functions. Use the IDA with linux binary to see what you can check in IDA with windows binary. Making a signature file is very easy. Which is more difficult is to find a function in windows. Not funny If I give you directly the offset. ^^ (but if you really don't get how to find the function, I will give the solution :p)
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