Replace Native Verifier by Bloom Filter

In this project, we show how replace a native verifier with a compact structure that can replicate the verifier behavior for all the proofs processed in the chain history for this verifier.

The project is structured like follow:

1. verifier-fixture crate contains the only dependency tha should be imported in the relay chain sources and provide the struct that can be built from binary data. In the tests provided in this crate you can find an example of how to instantiate the Fixture and use it to verify the proofs.

2. build-filter-example crate is a main program with a minimal CLI interface that

   1. fetch ultraplonk proofs
   2. create a filter
   3. serialize the filter
   4. deserialize the filter
   5. verify again all the proofs by using the filter

3. helpers crate that contains all the function that are used by the build-filter-example to fetch proof data. In general, to create a filter is not necessary to change this code but if you need to access to other vk storage you need also add the desired pallet in the verifiers.scale file. See at Download chain scale file for more details.

The build-filter-example program can be used as a template to create the filter data and save it. What you should provide is an implementation for the verifier that should cover the json deserialization and how to call the verify function. There will be some boilerplate that you should fix about types, but I chose to not make it generic and abstract to avoid unnecessary complications that could make it harder to understand.

Download chain scale file

We use subxt to interact with a zkverify node. In helpers/schemas/verifiers.scale we download the scale definition and in helpers::zkverify_node::zkverify we use subxt macro to build all the stuff needed to interact with. At the time we were writing we downloaded just SettlementUltraplonkPallet verifier information, but if you need to implement another verifier pallet your code should know how to interact with its Vks storage.

After installed subxt cli (look to subxt docs for more information) the following line is the one we use to download all we needed. We chose to select just these pallets to reduce the compile time, add just your pallet definition.

subxt metadata --url wss://volta-rpc.zkverify.io \
  -o helpers/schemas/verifiers.scale \
  --pallets SettlementUltraplonkPallet,System

Download subsquid graphql scheme

Maybe we'll never need it, but it's always good to know what the helpers/schemas/zkverify.graphql is and how to download it. Like the name says it's the GraphQL scheme of the service that we use to get all the extrinsic ID, the (block,id) tuple, where a submit_proof for a given verifier was submitted.

To download the schema we used the cynic CLI (see cynic docs for more details and how to install it)

cynic introspect http://localhost:4350/graphql -o helpers/schemas/zkverify.graphql

Our squids service provides also a playground at https://zkpvnetwork.squids.live/zkverify@v3/api/graphiql (pay attention to the i in graphiql) and cynic provides also a playground to write the rust code to build the query at https://generator.cynic-rs.dev/ .