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We use the proof as given in proof PIi in https://eprint.iacr.org/2016/013.pdf. This proof ws taken from the proof 6.3 (left side ) in https://www.cs.unc.edu/~reiter/papers/2004/IJIS.pdf
Statement: (c, pk, Q, G) witness (x, r) such that Q = xG, c = Enc(pk, x, r) note that because of the range proof, the proof has a slack in the range: x in [-q^3, q^3]