Binary Fuse filters as an alternative to BIP 158 GCS

This exploration is motivated by the potential for better CPU and bandwidth efficiency in light client applications. A benchmarking framework was developed using Core’s infrastructure to assess various set-membership algorithms, processing approximately 50,000 mainnet blocks and validating results against a ground truth to ensure accuracy. The findings suggest that Fuse16 significantly reduces CPU usage—by approximately 9 to 80 times on desktop and 6 to 45 times on ARM devices—while only slightly increasing bandwidth usage by about 0 to 3%. Despite this marginal increase in bandwidth, the CPU efficiency gains are substantial, raising questions about the trade-offs between CPU load and bandwidth consumption.

Further considerations include the potential complexity and privacy concerns of hierarchical constructions aimed at reducing bandwidth usage. Questions posed include the evaluation of CPU gains versus small bandwidth increases, possible oversights with the Binary Fuse approach, security implications, and the utility of refining the benchmarking framework to facilitate broader algorithm comparison. The feedback also highlights discrepancies in false positive rates between GCS and Binary Fuse filters, with suggestions for reaching parity by adjusting fingerprint sizes. Additionally, practical aspects such as targeted hash collisions and construction failures were discussed, indicating areas where the Binary Fuse strategy might be vulnerable or require further refinement.

Overall, the exchange underscores a robust interest and diverse insights into optimizing light client filters for Bitcoin, balancing performance improvements with potential risks and complexities. The conversation also reflects a commitment to open-source collaboration, with contributions from individuals transitioning from corporate environments to the open-source community, thereby enriching the discourse with fresh perspectives and empirical evaluations.