// Copyright (c) 2012 The Bitcoin developers // Distributed under the MIT/X11 software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #ifndef BITCOIN_BLOOM_H #define BITCOIN_BLOOM_H #include "serialize.h" #include <vector> class COutPoint; class CTransaction; class uint256; // 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001% static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes static const unsigned int MAX_HASH_FUNCS = 50; // First two bits of nFlags control how much IsRelevantAndUpdate actually updates // The remaining bits are reserved enum bloomflags { BLOOM_UPDATE_NONE = 0, BLOOM_UPDATE_ALL = 1, // Only adds outpoints to the filter if the output is a pay-to-pubkey/pay-to-multisig script BLOOM_UPDATE_P2PUBKEY_ONLY = 2, BLOOM_UPDATE_MASK = 3, }; /** * BloomFilter is a probabilistic filter which SPV clients provide * so that we can filter the transactions we sends them. * * This allows for significantly more efficient transaction and block downloads. * * Because bloom filters are probabilistic, an SPV node can increase the false- * positive rate, making us send them transactions which aren't actually theirs, * allowing clients to trade more bandwidth for more privacy by obfuscating which * keys are owned by them. */ class CBloomFilter { private: std::vector<unsigned char> vData; bool isFull; bool isEmpty; unsigned int nHashFuncs; unsigned int nTweak; unsigned char nFlags; unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const; public: // Creates a new bloom filter which will provide the given fp rate when filled with the given number of elements // Note that if the given parameters will result in a filter outside the bounds of the protocol limits, // the filter created will be as close to the given parameters as possible within the protocol limits. // This will apply if nFPRate is very low or nElements is unreasonably high. // nTweak is a constant which is added to the seed value passed to the hash function // It should generally always be a random value (and is largely only exposed for unit testing) // nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK) CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn); CBloomFilter() : isFull(true) {} IMPLEMENT_SERIALIZE ( READWRITE(vData); READWRITE(nHashFuncs); READWRITE(nTweak); READWRITE(nFlags); ) void insert(const std::vector<unsigned char>& vKey); void insert(const COutPoint& outpoint); void insert(const uint256& hash); bool contains(const std::vector<unsigned char>& vKey) const; bool contains(const COutPoint& outpoint) const; bool contains(const uint256& hash) const; void clear(); // True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS // (catch a filter which was just deserialized which was too big) bool IsWithinSizeConstraints() const; // Also adds any outputs which match the filter to the filter (to match their spending txes) bool IsRelevantAndUpdate(const CTransaction& tx); // Checks for empty and full filters to avoid wasting cpu void UpdateEmptyFull(); }; #endif /* BITCOIN_BLOOM_H */