Function prove_range 

pub fn prove_range(
    q: &BigUint,
    paillier: &PaillierPublicKey,
    ck: &CommitmentKey,
    c: &BigUint,
    m: &BigUint,
    r: &BigUint,
) -> RangeProof

Prove that c = Γ^m·r^N mod N² opens to m ∈ [0, q³).

r must be the exact Paillier randomness used to build c.