Function commit 

pub fn commit<E: Curve>(
    rng: &mut (impl RngCore + CryptoRng),
    gen1: Point<E>,
    gen2: Point<E>,
) -> (Commitment<E>, PrivateCommitment<E>)

First round of the protocol: commit to H by itself. Produces Commitment to be sent

rng is used to generate the nonce for the private commitment