Line data    Source code

       1             : // Copyright (c) 2012-2019 The Bitcoin Core developers
       2             : // Distributed under the MIT software license, see the accompanying
       3             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4             : 
       5             : #ifndef BITCOIN_BLOOM_H
       6             : #define BITCOIN_BLOOM_H
       7             : 
       8             : #include <serialize.h>
       9             : 
      10             : #include <vector>
      11             : 
      12             : class COutPoint;
      13             : class CTransaction;
      14             : class uint256;
      15             : 
      16             : //! 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001%
      17             : static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes
      18             : static const unsigned int MAX_HASH_FUNCS = 50;
      19             : 
      20             : /**
      21             :  * First two bits of nFlags control how much IsRelevantAndUpdate actually updates
      22             :  * The remaining bits are reserved
      23             :  */
      24             : enum bloomflags
      25             : {
      26             :     BLOOM_UPDATE_NONE = 0,
      27             :     BLOOM_UPDATE_ALL = 1,
      28             :     // Only adds outpoints to the filter if the output is a pay-to-pubkey/pay-to-multisig script
      29             :     BLOOM_UPDATE_P2PUBKEY_ONLY = 2,
      30             :     BLOOM_UPDATE_MASK = 3,
      31             : };
      32             : 
      33             : /**
      34             :  * BloomFilter is a probabilistic filter which SPV clients provide
      35             :  * so that we can filter the transactions we send them.
      36             :  *
      37             :  * This allows for significantly more efficient transaction and block downloads.
      38             :  *
      39             :  * Because bloom filters are probabilistic, a SPV node can increase the false-
      40             :  * positive rate, making us send it transactions which aren't actually its,
      41             :  * allowing clients to trade more bandwidth for more privacy by obfuscating which
      42             :  * keys are controlled by them.
      43             :  */
      44         101 : class CBloomFilter
      45             : {
      46             : private:
      47             :     std::vector<unsigned char> vData;
      48             :     unsigned int nHashFuncs;
      49             :     unsigned int nTweak;
      50             :     unsigned char nFlags;
      51             : 
      52             :     unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const;
      53             : 
      54             : public:
      55             :     /**
      56             :      * Creates a new bloom filter which will provide the given fp rate when filled with the given number of elements
      57             :      * Note that if the given parameters will result in a filter outside the bounds of the protocol limits,
      58             :      * the filter created will be as close to the given parameters as possible within the protocol limits.
      59             :      * This will apply if nFPRate is very low or nElements is unreasonably high.
      60             :      * nTweak is a constant which is added to the seed value passed to the hash function
      61             :      * It should generally always be a random value (and is largely only exposed for unit testing)
      62             :      * nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK)
      63             :      */
      64             :     CBloomFilter(const unsigned int nElements, const double nFPRate, const unsigned int nTweak, unsigned char nFlagsIn);
      65          18 :     CBloomFilter() : nHashFuncs(0), nTweak(0), nFlags(0) {}
      66             : 
      67          36 :     SERIALIZE_METHODS(CBloomFilter, obj) { READWRITE(obj.vData, obj.nHashFuncs, obj.nTweak, obj.nFlags); }
      68             : 
      69             :     void insert(const std::vector<unsigned char>& vKey);
      70             :     void insert(const COutPoint& outpoint);
      71             :     void insert(const uint256& hash);
      72             : 
      73             :     bool contains(const std::vector<unsigned char>& vKey) const;
      74             :     bool contains(const COutPoint& outpoint) const;
      75             :     bool contains(const uint256& hash) const;
      76             : 
      77             :     //! True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS
      78             :     //! (catch a filter which was just deserialized which was too big)
      79             :     bool IsWithinSizeConstraints() const;
      80             : 
      81             :     //! Also adds any outputs which match the filter to the filter (to match their spending txes)
      82             :     bool IsRelevantAndUpdate(const CTransaction& tx);
      83             : };
      84             : 
      85             : /**
      86             :  * RollingBloomFilter is a probabilistic "keep track of most recently inserted" set.
      87             :  * Construct it with the number of items to keep track of, and a false-positive
      88             :  * rate. Unlike CBloomFilter, by default nTweak is set to a cryptographically
      89             :  * secure random value for you. Similarly rather than clear() the method
      90             :  * reset() is provided, which also changes nTweak to decrease the impact of
      91             :  * false-positives.
      92             :  *
      93             :  * contains(item) will always return true if item was one of the last N to 1.5*N
      94             :  * insert()'ed ... but may also return true for items that were not inserted.
      95             :  *
      96             :  * It needs around 1.8 bytes per element per factor 0.1 of false positive rate.
      97             :  * (More accurately: 3/(log(256)*log(2)) * log(1/fpRate) * nElements bytes)
      98             :  */
      99        8032 : class CRollingBloomFilter
     100             : {
     101             : public:
     102             :     CRollingBloomFilter(const unsigned int nElements, const double nFPRate);
     103             : 
     104             :     void insert(const std::vector<unsigned char>& vKey);
     105             :     void insert(const uint256& hash);
     106             :     bool contains(const std::vector<unsigned char>& vKey) const;
     107             :     bool contains(const uint256& hash) const;
     108             : 
     109             :     void reset();
     110             : 
     111             : private:
     112             :     int nEntriesPerGeneration;
     113             :     int nEntriesThisGeneration;
     114             :     int nGeneration;
     115             :     std::vector<uint64_t> data;
     116             :     unsigned int nTweak;
     117             :     int nHashFuncs;
     118             : };
     119             : 
     120             : #endif // BITCOIN_BLOOM_H