# zkvote: Using ZK-SNARK to Implement Decentralized Anonymous Voting on p2p Network

zkvote-node: https://github.com/Unitychain/zkvote-node
zkvote-web: https://github.com/Unitychain/zkvote-web

## Architecture


- Cmd
- zkvote(pkg)
- Service(pkg)
- Node.go
- manager(pkg)
- Manager(Collector).go
- subject_protocol.go
- identity_protocol.go
- voter(pkg)
- Voter.go
- IdentityPool(IdentityIMP).go
- Proposal.go
- zksnark(pkg)
- Verifier.go
- Store(pkg)
- Validator.go
- Store.go
- utils(pkg)
- crypto(pkg)
- Model(pkg)
- Subject.go
- Identity.go
- MerkelTree.go
- Context.go
- pb(pkg)
- zkvote.proto
- restapi(pkg)
- Controller
- Model

## Technical Details
- Run `zkvote-node`. The node `K` will connect to other peers in the network.
- Nodes form two networks: DHT and pub/sub
- The local running node provides a web UI for the user to register and submit proof.
- A pub/sub topic is a voting subject
- Use `Discovery` package to look up peers that are topic providers. See [Notes on go-libp2p-discovery](/@juincc/Hk_0PWFhS)
- Setup a stream from the joining node and to the topic providers
- Topic provides respond their pub/sub topics
- The joining node can either
- Subscribe to one of the existing topic
- Start a new topic, this will make the joining node become one of the topic provider
- Attach a description to a topic
- Store the description locally
- key: topic, value: description
- Respond to the requestor as well as the topic name
- How the p2p network is formed?
- as layer 1 solution => need consensus (zkvote doesn't have)
- as layer 2 solution => no need for p2p network and need to put the proof back to blockchain (zkvote doesn't have)
- need blockchain for DID anyway. L2 is more elegant.
- How to verify JWT on zkvote-node?
- See `aries-framework-go`
- Does not support DID method `ethr`
- Verify VC on zkvote-web
- Does the node have to resolve the DID doc?
- What are in the DID doc?
- See https://www.w3.org/TR/did-core/#did-documents
- How to exchange VC?
- VC should be stored in a DID hub
- To make it simple: Copy and paste a raw JWT
- What is the content of the ballot VC?
- The public key and sugnature of the proposer
- Need PKI or PGP?
- The public key of the voting person
- How to manage private key/DID/zkvote Identity?:
1. Generate Ethereum private key
- Use `ethr-did`
- Generate the keypair on zkvote-web and show on the console
2. Generate DID
- Use `ethr-did`
- Derived from Ethereum keypair
- Show on console
3. Generate zkvote identity
- Use generated private key as the secret
- **Question: Some identities are not vlidated by zkvote-node. Why?**
- VC
- Proposer can issue VC for a subject
- Voter has to present the VC received from the proposer to vote on a subject
- Need PKI to check if the issuer is the proposer?

## Questions
### Why use DHT?
- No need for consensus or blockchain in this PoC
- Still need a global state
- DHT is efficient and easier to implement
- go-libp2p supports Kademlia
- Pure file/data sharing application

## Does voting need consensus?
- Voting has 2 step: Registry and Proof
- How to register?
- How to prevent sybil?
- Registry is just as simple as storing its key on DHT.
- Some verifiable personal info
- Registry message has to be signed to provide the intigrity and non-repudiation
- Construct the registry list from DHT
- Can DHT query a namespace?

### Is DHT necessary if pub/sub is used?
- DHT is more efficient only if the size of the subscription is greater than `k` (k=20 for default)
- __Pub/sub is necessary for indexing proofs.__
- __Proofs are stored in the DHT, use pub/sub to index the topic and the stored proof__. Nodes that belongs to the same topic will maintain the same set of index

### Does every participant have to run a node?
- the sig reveals the identity, no privacy any more
- use some nodes to be relay?

## Todo
- Implement VC rules to make it permissioned
- global identity, add different rules to build local(subject) identities
- **zkvote can act as a layer 2. Use zk-rollup to put the proof on blockchain**
- Layer 2 needs incentive model
### Refactor
- Extract db logic from `Manager`
- Extract network logic from `Manager` and `Voter`

### Feature
- CLI
- Which one? Cobra / Cli / go-ipfs-cmds
- Store published message locally
- Implement a consensus layer
- Sign on the value
- Implement a validator that can verify sig
- Figure out how validator `pk` works
- Implement API for CLI debugger

## Challenges
- What if the provider of one topic `A` goes offline?
- Only the original topic initiator has to provide? Or, several provides of one topic `A` have to provide?
- __How to deprecate subjects?__
- __How to register the identity globally?__
- So far we only register in individual pub/sub network.
- What is the best strategy for syncing the identity merkle tree
- How to generate identity commitment efficiently?
- Should be able to delegate the role of subject creator?
- How to manage keys?
- How to prevent sybil attack?

## Experts in this field
- Barry Whitehat
- Oskar
- Mikerah
- ...

## Reference
- [Private voting and whistleblowing on Ethereum using Semaphore](https://medium.com/@weijiek/private-voting-and-whistleblowing-in-ethereum-using-semaphore-449b376808e)
- [Notes on kad_node](/9P77VeMYTF6NTOHwsvHqUg)
- [go-snark](https://github.com/arnaucube/go-snark)
- [go-libp2p](https://github.com/libp2p/go-libp2p)
- [Semaphore](https://github.com/kobigurk/semaphore)
- [Circom](https://github.com/iden3/circom)
- [libp2p pubsub](https://docs.libp2p.io/concepts/publish-subscribe/)
- [libp2p-p2p-daemon](https://github.com/libp2p/go-libp2p-daemon)
- [STATE OF THE MIXERS: SUMMER 2019](https://github.com/tvanepps/State-of-the-Mixers-Summer-2019/blob/master/README.md)
- [Baidu DID](https://did.baidu.com/)

###### tags: `unitychain` `poc` `p2p` `zkp` `dht`