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I have a question about ECC based DLP.

I know that getting k is hard when kG is known. (G is a generator)


Question.

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

or that getting k where x is known?

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

Thanks

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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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