Where does the 33.33% threshold for selfish mining come from?

The concept of Fibre miners impacting the efficiency and fairness of block propagation in cryptocurrency networks brings to light concerns about potential "selfish mining" practices. These miners, by utilizing Fibre for superior connectivity, may not be overtly withholding blocks to gain additional mining time; however, the resultant effect closely mirrors this strategy. This subtle advantage allows them to attain approximately 0.03% excess profit from the portion of the network not employing Fibre, based on a calculated profit margin that considers the network's composition and mining dynamics.

A critical aspect of this discussion revolves around the delay Fibre miners introduce when releasing blocks. While they might not intentionally delay block propagation to other Fibre miners, thereby not affecting each other's chances, this practice disadvantages non-Fibre miners. The mechanics of this situation reveal that if a Fibre miner discovers a block, there is an inherent delay before this information becomes available to a non-Fibre miner. This delay grants Fibre miners a brief period where they have an exclusive opportunity to continue mining, furthering their lead over their non-Fibre counterparts. Consequently, this disparity can lead to a significant loss in potential rewards for non-Fibre miners, quantified as a 0.1% reduction in rewards due to the calculated delays in block visibility.

To delve deeper into the implications of these delays, one can analyze the rate of stale blocks within the network. Stale blocks serve as an indicator of inefficiency in block propagation, where blocks are discovered but not included in the blockchain. By examining data from sources such as fork.observer and the bitcoin-data stale-blocks repository, insights into the frequency of stale blocks provide evidence of the potential manipulation of block release timings by Fibre miners. This analysis suggests an observed delay that significantly exceeds what would be expected under normal circumstances, pointing towards a deliberate attempt to secure minor profits through strategic block release delays.

Furthermore, the investigation into the discrepancy between expected and observed stale block rates underlines the complexity of accurately assessing the impact of such strategies. The calculation of delays, based on empirical data and mathematical modeling, illustrates a nuanced understanding of how Fibre miners might be exploiting their technological edge to outpace non-Fibre miners subtly. This exploitation, while seemingly marginal in terms of individual gains, underscores a broader issue of equity and fairness within the mining ecosystem, potentially skewing rewards in favor of those with advanced infrastructure.