I have a question about EC-based DLP. I know that getting $k$ is hard when $kG$ is known. ($G$ is a generator)


Is it still hard getting $kG$ where $x$ is known? (in here, $kG=(x,y)$) or getting $k$ where $x$ is known?

I think the former is not computationally hard. Am I right?


1 Answer 1


For a given x there are only two possible y coordinates figuring that out is just a matter of solving the curve equation for y.

Afterwards you just end up with a regular DLOG problem which is hard (if your x is for a point with large enough order order your curve order is prime).


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