todo list of make the verifier production usable on aptos

[nanne007]

Although we had verified the correctness of the verifier.
Still many problems to be resolved to make it usable on aptos mainnet.

• aptos limit on elments mem usage during a session. see address the issue of too many elements #47
• the problem of different serialization of bn254 curve point between halo2 and arkworks.
• to solve the problem above, we have to calculate Y based on X which needs a sqrt function on base field. That's missing on atpos. we implemented it with a pow(u256),

  halo2-verifier.move/sources/bn254_utils.move

  Line 55 in ac00bde

  public fun sqrt_fq(self: &Element<Fq>): Option<Element<Fq>> {

  which has very low efficiency.
• currently, we implement pow function with pure move,

  halo2-verifier.move/sources/bn254_utils.move

  Line 64 in ac00bde

  fun pow<F>(self: &Element<F>, exp: &vector<u64>): Element<F> {

  which can consume many gas when the power is big. should be optimized.
• currently, we cannot store a crypto element in state. Had to store them in serialized form. It's inconvenient for developers.

[nanne007]

we will cooperate with devs of aptos to finish the job.
will start from Feb or Mar.