Hello list, Here is a link for a draft of a BIP for compact probabilistic block filters alternative of BIP 158
https://docs.google.com/document/d/1jH9tEUyb9w2OZd4-kxfGuyNIIZzmgkEb_z0qSxv80ik/edit?usp=sharing <https://docs.google.com/document/d/1jH9tEUyb9w2OZd4-kxfGuyNIIZzmgkEb_z0qSxv80ik/edit?usp=sharing> Summary: - BIP 158 false positive rate is low, we can achieve lower bandwidth with higher false positive rate filter while sync blockchain - BIP 158 not do not support filter batching by design of used parameters for siphash and Golomb coding optimal parameters - Alternative compression with delta coding and splitting data to 2 bit string sequences. First for data without prefixes, second one for information about bit length written to first sequence. Second sequence have a lot of duplicates, compressed with 2 round of Huffman algorithm. (Effectivity about 98% vs Golomb with optimal parameters) - Block filters batching reduce filter size significantly - Separation of filters by address type allows lite client not to download redundant information without compromising privacy. - Lite client filters download strategy: get biggest filter (smallest blocks/size rate) for blocks range, in case positive test -> get medium filters to reduce blocks range -> get block filters for affected range -> download affected blocks over TOR Implementation (python): https://github.com/bitaps-com/pybtc/blob/bugfix/pybtc/functions/filters.py#L172 <https://github.com/bitaps-com/pybtc/blob/bugfix/pybtc/functions/filters.py#L172> Exactly information from mainnet about size for separated filters by address types and batch size will be added within few days. Thanks for any feedback. Aleksey Karpov
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