Bulletin boards are a key component of cryptographically secure, end-to-end verifiable voting systems. The bulleting board is a storage system where all the public information relative to the election is published for anyone to see, review and audit. In end-to-end verifiable voting systems the bulletin board contains the information necessary to verify that the election was carried out according to established protocols, to ensure the correctness of the reported outcome and that no manipulation by administrators or any other entities took place.
The bulletin board typically stores information such as public key and key generation details, voting events and encrypted votes, decryption and tally results, along with mathematically verifiable proofs that all of the above are correct. Additionally the board usually serves as an audit ledger as well, registering any significant event and actions taken that can be reviewed by anyone.
There are some desirable properties that bulletin boards must have to better meet their objectives:
This allows operation of an election to continue despite DDOS attacks. This is the hardest property to achieve, as hard problems such as byzantine consensus need to be solved, as well as engineering challenges related to distribution.
The bulletin board should support logging of events and data in a way that reflects its order in time.
No one should be able to alter the bulletin board records in order to manipulate results or remove records from the audit log.
4) Publically auditable
The bulletin board information should be auditable by anyone. In particular, the election’s end-to-end verifiability should be supported by this property.
5) Access controlled and authenticated
The bulletin board should include mechanisms to control who can post what information, as well as digital signatures of said information and of receipts for ceritified publishing.
An interesting research project could be to investigate what properties blockchain technologies can provide as fundamental components of a robust bulletin board. In particular blockchain technology seems especially well positioned to satisfy distribution, chronology, tamper reistance, and auditing, as well as offering some support for signatures. It would also be necessary to evaluate efficiency considerations as to number of “transactions” processed per second such that the throughput is compatible with voting needs.