  This paper proposes the first hash opinion dynamics model, named SkyHash,
that can help a P2P network quickly reach consensus on hash opinion. The model
consists of a bit layer and a hash layer, each time when a node shapes its new
opinion, the bit layer is to determine each bit of a pseudo hash, and the hash
layer is to choose a hash opinion with minimum Hamming distance to the pseudo
hash. With simulations, we conducted a comprehensive study on the convergence
speed of the model by taking into account impacts of various configurations
such as network size, node degree, hash size, and initial hash density.
Evaluation demonstrates that using our model, consensus can be quickly reached
even in large networks. We also developed a denial-of-service (DoS) proof
extension for our model. Experiments on the SNAP dataset of the Wikipedia
who-votes-on-whom network demonstrate that besides the ability to refuse known
ill-behaved nodes, the DoS-proof extended model also outperforms Bitcoin by
producing consensus in 45 seconds, and tolerating DoS attack committed by up to
0.9% top influential nodes.
