Browse Source

Add a CBloomFilter class for use as a transaction filter.

tags/v0.15.1
Matt Corallo 8 years ago
parent
commit
bd21612c37
7 changed files with 209 additions and 0 deletions
  1. 2
    0
      bitcoin-qt.pro
  2. 133
    0
      src/bloom.cpp
  3. 70
    0
      src/bloom.h
  4. 1
    0
      src/makefile.linux-mingw
  5. 1
    0
      src/makefile.mingw
  6. 1
    0
      src/makefile.osx
  7. 1
    0
      src/makefile.unix

+ 2
- 0
bitcoin-qt.pro View File

@@ -155,6 +155,7 @@ HEADERS += src/qt/bitcoingui.h \
src/script.h \
src/init.h \
src/irc.h \
src/bloom.h \
src/mruset.h \
src/json/json_spirit_writer_template.h \
src/json/json_spirit_writer.h \
@@ -223,6 +224,7 @@ SOURCES += src/qt/bitcoin.cpp src/qt/bitcoingui.cpp \
src/init.cpp \
src/net.cpp \
src/irc.cpp \
src/bloom.cpp \
src/checkpoints.cpp \
src/addrman.cpp \
src/db.cpp \

+ 133
- 0
src/bloom.cpp View File

@@ -0,0 +1,133 @@
// 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.
#include <math.h>
#include <stdlib.h>

#include "bloom.h"
#include "main.h"
#include "script.h"

#define LN2SQUARED 0.4804530139182014246671025263266649717305529515945455
#define LN2 0.6931471805599453094172321214581765680755001343602552

using namespace std;

static const unsigned char bit_mask[8] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};

CBloomFilter::CBloomFilter(unsigned int nElements, double nFPRate) :
// The ideal size for a bloom filter with a given number of elements and false positive rate is:
// - nElements * log(fp rate) / ln(2)^2
// We ignore filter parameters which will create a bloom filter larger than the protocol limits
vData(min((unsigned int)(-1 / LN2SQUARED * nElements * log(nFPRate)), MAX_BLOOM_FILTER_SIZE * 8) / 8),
// 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 http://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas
nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS))
{
}

inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const
{
// 0xFBA4C795 chosen as it guarantees a reasonable bit difference between nHashNum values.
return MurmurHash3(nHashNum * 0xFBA4C795, vDataToHash) % (vData.size() * 8);
}

void CBloomFilter::insert(const vector<unsigned char>& vKey)
{
for (unsigned int i = 0; i < nHashFuncs; i++)
{
unsigned int nIndex = Hash(i, vKey);
// Sets bit nIndex of vData
vData[nIndex >> 3] |= bit_mask[7 & nIndex];
}
}

void CBloomFilter::insert(const COutPoint& outpoint)
{
CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
stream << outpoint;
vector<unsigned char> data(stream.begin(), stream.end());
insert(data);
}

void CBloomFilter::insert(const uint256& hash)
{
vector<unsigned char> data(hash.begin(), hash.end());
insert(data);
}

bool CBloomFilter::contains(const vector<unsigned char>& vKey) const
{
for (unsigned int i = 0; i < nHashFuncs; i++)
{
unsigned int nIndex = Hash(i, vKey);
// Checks bit nIndex of vData
if (!(vData[nIndex >> 3] & bit_mask[7 & nIndex]))
return false;
}
return true;
}

bool CBloomFilter::contains(const COutPoint& outpoint) const
{
CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
stream << outpoint;
vector<unsigned char> data(stream.begin(), stream.end());
return contains(data);
}

bool CBloomFilter::contains(const uint256& hash) const
{
vector<unsigned char> data(hash.begin(), hash.end());
return contains(data);
}

bool CBloomFilter::IsWithinSizeConstraints() const
{
return vData.size() <= MAX_BLOOM_FILTER_SIZE && nHashFuncs <= MAX_HASH_FUNCS;
}

bool CBloomFilter::IsTransactionRelevantToFilter(const CTransaction& tx) const
{
// Match if the filter contains the hash of tx
// for finding tx when they appear in a block
if (contains(tx.GetHash()))
return true;

BOOST_FOREACH(const CTxOut& txout, tx.vout)
{
// Match if the filter contains any arbitrary script data element in any scriptPubKey in tx
CScript::const_iterator pc = txout.scriptPubKey.begin();
vector<unsigned char> data;
while (pc < txout.scriptPubKey.end())
{
opcodetype opcode;
if (!txout.scriptPubKey.GetOp(pc, opcode, data))
break;
if (data.size() != 0 && contains(data))
return true;
}
}

BOOST_FOREACH(const CTxIn& txin, tx.vin)
{
// Match if the filter contains an outpoint tx spends
if (contains(txin.prevout))
return true;

// Match if the filter contains any arbitrary script data element in any scriptSig in tx
CScript::const_iterator pc = txin.scriptSig.begin();
vector<unsigned char> data;
while (pc < txin.scriptSig.end())
{
opcodetype opcode;
if (!txin.scriptSig.GetOp(pc, opcode, data))
break;
if (data.size() != 0 && contains(data))
return true;
}
}

return false;
}

+ 70
- 0
src/bloom.h View File

@@ -0,0 +1,70 @@
// 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 <vector>

#include "uint256.h"
#include "serialize.h"

class COutPoint;
class CTransaction;

// 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;


/**
* 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;
unsigned int nHashFuncs;

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.
CBloomFilter(unsigned int nElements, double nFPRate);
// Using a filter initialized with this results in undefined behavior
// Should only be used for deserialization
CBloomFilter() {}

IMPLEMENT_SERIALIZE
(
READWRITE(vData);
READWRITE(nHashFuncs);
)

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;

// 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;

bool IsTransactionRelevantToFilter(const CTransaction& tx) const;
};

#endif /* BITCOIN_BLOOM_H */

+ 1
- 0
src/makefile.linux-mingw View File

@@ -84,6 +84,7 @@ OBJS= \
obj/walletdb.o \
obj/noui.o \
obj/hash.o \
obj/bloom.o \
obj/leveldb.o \
obj/txdb.o


+ 1
- 0
src/makefile.mingw View File

@@ -79,6 +79,7 @@ OBJS= \
obj/wallet.o \
obj/walletdb.o \
obj/hash.o \
obj/bloom.o \
obj/noui.o \
obj/leveldb.o \
obj/txdb.o

+ 1
- 0
src/makefile.osx View File

@@ -97,6 +97,7 @@ OBJS= \
obj/wallet.o \
obj/walletdb.o \
obj/hash.o \
obj/bloom.o \
obj/noui.o \
obj/leveldb.o \
obj/txdb.o

+ 1
- 0
src/makefile.unix View File

@@ -128,6 +128,7 @@ OBJS= \
obj/wallet.o \
obj/walletdb.o \
obj/hash.o \
obj/bloom.o \
obj/noui.o \
obj/leveldb.o \
obj/txdb.o

Loading…
Cancel
Save