BloomFilter is a probabilistic filter which SPV clients provide so that we can filter the transactions we send them. More...

#include <bloom.h>

Public Member Functions
	CBloomFilter (const unsigned int nElements, const double nFPRate, const unsigned int nTweak, unsigned char nFlagsIn)
	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. More...

	CBloomFilter ()

	SERIALIZE_METHODS (CBloomFilter, obj)

void	insert (Span< const unsigned char > vKey)

void	insert (const COutPoint &outpoint)

bool	contains (Span< const unsigned char > vKey) const

bool	contains (const COutPoint &outpoint) const

bool	IsWithinSizeConstraints () const
	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) More...

bool	IsRelevantAndUpdate (const CTransaction &tx)
	Also adds any outputs which match the filter to the filter (to match their spending txes) More...

Private Member Functions
unsigned int	Hash (unsigned int nHashNum, Span< const unsigned char > vDataToHash) const

Private Attributes
std::vector< unsigned char >	vData

unsigned int	nHashFuncs

unsigned int	nTweak

unsigned char	nFlags

Detailed Description

BloomFilter is a probabilistic filter which SPV clients provide so that we can filter the transactions we send them.

This allows for significantly more efficient transaction and block downloads.

Because bloom filters are probabilistic, a SPV node can increase the false- positive rate, making us send it transactions which aren't actually its, allowing clients to trade more bandwidth for more privacy by obfuscating which keys are controlled by them.

Definition at line 44 of file bloom.h.

Constructor & Destructor Documentation

◆ CBloomFilter() [1/2]

CBloomFilter::CBloomFilter	(	const unsigned int	nElements,
		const double	nFPRate,
		const unsigned int	nTweakIn,
		unsigned char	nFlagsIn
	)

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.

The ideal size for a bloom filter with a given number of elements and false positive rate is:

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)

nElements * log(fp rate) / ln(2)^2 We ignore filter parameters which will create a bloom filter larger than the protocol limits The ideal number of hash functions is filter size * ln(2) / number of elements Again, we ignore filter parameters which will create a bloom filter with more hash functions than the protocol limits See https://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas

Definition at line 25 of file bloom.cpp.

◆ CBloomFilter() [2/2]

CBloomFilter::CBloomFilter ( )

inline

Definition at line 65 of file bloom.h.