# Competing (Semi)-Selfish Miners in Bitcoin

## TL;DR

This paper extends the analysis of selfish mining in Bitcoin to multiple non-colluding miners, revealing that collective strategic deviations can outperform honest mining and compromise network security.

## Contribution

It introduces a model for multiple selfish miners in Bitcoin and demonstrates how their combined strategies can undermine protocol security.

## Key findings

- Multiple selfish miners can outperform honest miners collectively.
- Strategic deviations by several miners can threaten Bitcoin's security.
- The protocol is less secure against coordinated selfish strategies.

## Abstract

The Bitcoin protocol prescribes certain behavior by the miners who are responsible for maintaining and extending the underlying blockchain; in particular, miners who successfully solve a puzzle, and hence can extend the chain by a block, are supposed to release that block immediately. Eyal and Sirer showed, however, that a selfish miner is incentivized to deviate from the protocol and withhold its blocks under certain conditions. The analysis by Eyal and Sirer, as well as in followup work, considers a \emph{single} deviating miner (who may control a large fraction of the hashing power in the network) interacting with a remaining pool of honest miners. Here, we extend this analysis to the case where there are \emph{multiple} (non-colluding) selfish miners. We find that with multiple strategic miners, specific deviations from honest mining by multiple strategic agents can outperform honest mining, even if individually miners would not be incentivised to be dishonest. This previous point effectively renders the Bitcoin protocol to be less secure than previously thought.