There are several ways one could imagine deploying such a system. In each case, the issuance mechanism is probably bespoke. One example of issuance is where you have some pre-existing way of knowing that someone is within some group.
For example, a government could issue credentials to individuals based on their identity documents. As another example, a company could issue credentials based on their membership in the firm.
For some friends who want to deploy anonymous voting for their use cases, just some random server is a totally reasonable way to deploy this system. In particular, just have someone you trust set up a server which collects and verifies votes. If users feel extra paranoid about the server actually capturing and recording who voted for what via fingerprinting of some sort, then they can connect to the server via a VPN.
If you want to get fancy, OHTTP might be a useful thing. I need to learn more about this.
This is a great use case for a Trusted Execution Environment. In particular, we can deploy a single vote collector in a Trusted Execution Environment that only permits votes to be cast up to a certain time, and after that time allows arbitrary clients to query the vote set.
However, it is important to note that such a system has another root of trust, the hardware provider. In a use case such as governmental elections, this root of trust might not be appropriate.
This is probably the most straightforward deployment option. Essentially, you deploy a smart contract which accepts and verifies votes. At a certain time, the contract stops accepting votes and then everyone can observe which candidate got the most votes by just counting from the list on chain. Further, the smart contract can have some convenience functions for calculating who won for you, and you can trust this if you trust the smart contract.
Nodes can censor users who are voting in ways they don't prefer. In practice, unless a network is highly centralized, this is likely not a problem for practical deployments. For use cases which have broad impact, like government elections, this should strongly be taken into account. However, for a small group holding anonymous elections on some mostly irrelevant thing to the nodes, it seems like this is a perfectly appropriate deployment pattern.
Another approach is to build a bespoke system to solve this problem. This is much harder, and requires careful thought to avoid issues such as:
- Censorship, as in the blockchain case
- Voting after expiration, which is stopped in the blockchain approach by including transactions in a block where we also have a timestamp
I'll try to write up a design for this soon, but I want to make sure I get it right, ideally with a proof of correctness.