@ -203,7 +203,7 @@ Shortly after the introduction of SPV/lightweight nodes, the bitcoin developers
[[bloom_filters]]
=== Bloom Filters
((("bitcoin network", "bloom filters", id="BNebloom08")))A bloom filter is a probabilistic search filter, a way to describe a desired pattern without specifying it exactly. Bloom filters offer an efficient way to express a search pattern while protecting privacy. They are used by SPV nodes to ask their peers for transactions matching a specific pattern, without revealing exactly which addresses, keys, or transactions they are searching for.
((("bitcoin network", "bloom filters", id="BNebloom08")))((("bloom filters", id="bloom08")))A bloom filter is a probabilistic search filter, a way to describe a desired pattern without specifying it exactly. Bloom filters offer an efficient way to express a search pattern while protecting privacy. They are used by SPV nodes to ask their peers for transactions matching a specific pattern, without revealing exactly which addresses, keys, or transactions they are searching for.
In our previous analogy, a tourist without a map is asking for directions to a specific address, "23 Church St." If she asks strangers for directions to this street, she inadvertently reveals her destination. A bloom filter is like asking, "Are there any streets in this neighborhood whose name ends in R-C-H?" A question like that reveals slightly less about the desired destination than asking for "23 Church St." Using this technique, a tourist could specify the desired address in more detail as "ending in U-R-C-H" or less detail as "ending in H." By varying the precision of the search, the tourist reveals more or less information, at the expense of getting more or less specific results. If she asks a less specific pattern, she gets a lot more possible addresses and better privacy, but many of the results are irrelevant. If she asks for a very specific pattern, she gets fewer results but loses privacy.
@ -274,7 +274,7 @@ As the full node sends transactions to the SPV node, the SPV node discards any f
The node setting the bloom filter can interactively add patterns to the filter by sending a +filteradd+ message. To clear the bloom filter, the node can send a +filterclear+ message. Because it is not possible to remove a pattern from a bloom filter, a node has to clear and resend a new bloom filter if a pattern is no longer desired.
The network protocol and bloom filter mechanism for SPV nodes is defined in https://github.com/bitcoin/bips/blob/master/bip-0037.mediawiki[BIP-37 (Peer Services)].((("", startref="BNebloom08")))
The network protocol and bloom filter mechanism for SPV nodes is defined in https://github.com/bitcoin/bips/blob/master/bip-0037.mediawiki[BIP-37 (Peer Services)].((("", startref="BNebloom08")))((("", startref="bloom08")))
judymcconville@roadrunner.com
7 years ago