A Generic Interface for the Public Bulletin Board Used in UniVote

To provide verifiability, cryptographic voting protocols usually require a public bulletin board forpublishing the election data, so that the data can be read and verified by everyone. The basic requirements onsuch a board are similar for most protocols, for example that nothing can be changed or deleted from the board. Typically, when it comes to implement a voting protocol in a real system, many additional requirements ariseand they can differ from protocol to protocol. This paper shows based on the protocol of UniVote what theserequirements might be and what other problems may arise from an operational and organisational point ofview. Based on the understanding of these problems, we propose a generic interface for the main boardfunctionalities. This interface offers a flexible way of extending the properties of a public bulletin board tocomply with all sorts of additional requirements. We give multiple examples of properties that we identified asdesirable for the public bulletin board in UniVote.