Efficient Polling Protocol for Decentralized Social Networks

We address the polling problem in social networks where individuals collaborate to choose the most favorite choice amongst some options, without divulging their vote and publicly exposing their potentially malicious actions. Given this social interaction model, Guerraoui et al. recently proposed polling protocols that do not rely on any central authority or cryptography system, using a simple secret sharing scheme along with verification procedures to accurately compute the poll’s final result. However, these protocols can be deployed safely and efficiently provided that, inter alia, the social graph structure should be transformed into a ring structure-based overlay and the number of participating users is perfect square. Consequently, designing \emph{secure} and \emph{efficient} polling protocols regardless these constraints remains a challenging issue. In this paper, we present EPol, a simple decentralized polling protocol that relies on the current state of social graphs. More explicitly, we define one family of social graphs that satisfy what we call the $m$-broadcasting property (where $m$ is less than or equal to the minimum node degree) and show their structures enable low communication cost and constitute necessary and sufficient condition to ensure vote privacy and limit the impact of dishonest users on the accuracy of the polling output. Our protocol is effective to compute more precisely the final result. Furthermore, despite the use of richer social graph structures, the communication and spatial complexities of EPol are close to be linear.

💡 Research Summary

The paper tackles the problem of conducting a secure poll in a decentralized online social network (OSN) without relying on a central authority or cryptographic primitives. Existing solutions such as DPol and its derivatives require a ring‑based overlay and a perfect‑square number of participants, which limits their practicality. The authors propose a new protocol, EPol, that operates directly on the underlying social graph and removes these constraints.

Key Contributions

1. m‑broadcasting Property – The authors define a structural condition for graphs: a graph satisfies the m‑broadcasting property (with 1 ≤ m ≤ d_min, where d_min is the minimum node degree) if, for any source node, there exists a topological ordering of the nodes such that each node is either directly connected to the source or connected to at most m preceding nodes in that order. This property guarantees that during a broadcast each node stores at most m copies of a message, preventing exponential growth of local storage and keeping communication overhead near‑linear.

2. Protocol Design – Each honest participant splits its vote (±1) into an odd number (2i + 1) of shares, where i ∈