Address ethical concerns using zkSNARK

[burdges]

It's unethical to post government identifiers like a person's EID public key onto a public blockchain, so

You'll need a zkSNARK circuit that proves roughly the NP statement

{ (ETH_PK, H("Ethereum" ++ EID_pk)) : ECDSAVerify(EID_pk,ETH_pk), whatever else }

I've created an Arkworks issue for discussing the necessary curves at arkworks-rs/curves#82

You guys would require Arkwork's non-native curve arithmetic tooling to use Etherem's bn254 pairings, while we could use bespoke curves in Polkadot, but Arkwork's clean abstractions align our interests somewhat.

In Ethereum speak, I'm proposing you do a zk roll up of checking the signature and certificate chain. Aside from this being more ethical, it also resolves your gas problem in #3 by verifying only a Groth16 proof, so three pairings plus two scalar multiplications.