Line data    Source code

       1             : // Copyright (c) 2012-2014 The Bitcoin developers
       2             : // Copyright (c) 2017-2020 The PIVX Core developers
       3             : // Distributed under the MIT software license, see the accompanying
       4             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       5             : 
       6             : #ifndef PIVX_BLOOM_H
       7             : #define PIVX_BLOOM_H
       8             : 
       9             : #include "serialize.h"
      10             : 
      11             : #include <vector>
      12             : 
      13             : class COutPoint;
      14             : class CTransaction;
      15             : class uint256;
      16             : 
      17             : //! 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001%
      18             : static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes
      19             : static const unsigned int MAX_HASH_FUNCS = 50;
      20             : 
      21             : /**
      22             :  * First two bits of nFlags control how much IsRelevantAndUpdate actually updates
      23             :  * The remaining bits are reserved
      24             :  */
      25             : enum bloomflags {
      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 sends them.
      36             :  *
      37             :  * This allows for significantly more efficient transaction and block downloads.
      38             :  *
      39             :  * Because bloom filters are probabilistic, an SPV node can increase the false-
      40             :  * positive rate, making us send them transactions which aren't actually theirs,
      41             :  * allowing clients to trade more bandwidth for more privacy by obfuscating which
      42             :  * keys are owned by them.
      43             :  */
      44        2457 : class CBloomFilter
      45             : {
      46             : private:
      47             :     std::vector<unsigned char> vData;
      48             :     bool isFull;
      49             :     bool isEmpty;
      50             :     unsigned int nHashFuncs;
      51             :     unsigned int nTweak;
      52             :     unsigned char nFlags;
      53             : 
      54             :     unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const;
      55             : 
      56             : public:
      57             :     /**
      58             :      * Creates a new bloom filter which will provide the given fp rate when filled with the given number of elements
      59             :      * Note that if the given parameters will result in a filter outside the bounds of the protocol limits,
      60             :      * the filter created will be as close to the given parameters as possible within the protocol limits.
      61             :      * This will apply if nFPRate is very low or nElements is unreasonably high.
      62             :      * nTweak is a constant which is added to the seed value passed to the hash function
      63             :      * It should generally always be a random value (and is largely only exposed for unit testing)
      64             :      * nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK)
      65             :      */
      66             :     CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn);
      67        1464 :     CBloomFilter() : isFull(true), isEmpty(false), nHashFuncs(0), nTweak(0), nFlags(0) {}
      68             : 
      69           3 :     SERIALIZE_METHODS(CBloomFilter, obj) { READWRITE(obj.vData, obj.nHashFuncs, obj.nTweak, obj.nFlags); }
      70             : 
      71             :     void insert(const std::vector<unsigned char>& vKey);
      72             :     void insert(const COutPoint& outpoint);
      73             :     void insert(const uint256& hash);
      74             : 
      75             :     bool contains(const std::vector<unsigned char>& vKey) const;
      76             :     bool contains(const COutPoint& outpoint) const;
      77             :     bool contains(const uint256& hash) const;
      78             : 
      79             :     void clear();
      80             :     void reset(unsigned int nNewTweak);
      81             : 
      82             :     //! True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS
      83             :     //! (catch a filter which was just deserialized which was too big)
      84             :     bool IsWithinSizeConstraints() const;
      85             : 
      86             :     bool Merge(const CBloomFilter& filter);
      87             :     bool MatchesAll() const;
      88             : 
      89             :     //! Also adds any outputs which match the filter to the filter (to match their spending txes)
      90             :     bool IsRelevantAndUpdate(const CTransaction& tx);
      91             : 
      92             :     //! Checks for empty and full filters to avoid wasting cpu
      93             :     void UpdateEmptyFull();
      94             : };
      95             : 
      96             : /**
      97             :  * RollingBloomFilter is a probabilistic "keep track of most recently inserted" set.
      98             :  * Construct it with the number of items to keep track of, and a false-positive
      99             :  * rate. Unlike CBloomFilter, by default nTweak is set to a cryptographically
     100             :  * secure random value for you. Similarly rather than clear() the method
     101             :  * reset() is provided, which also changes nTweak to decrease the impact of
     102             :  * false-positives.
     103             :  *
     104             :  * contains(item) will always return true if item was one of the last N to 1.5*N
     105             :  * insert()'ed ... but may also return true for items that were not inserted.
     106             :  *
     107             :  * It needs around 1.8 bytes per element per factor 0.1 of false positive rate.
     108             :  * (More accurately: 3/(log(256)*log(2)) * log(1/fpRate) * nElements bytes)
     109             :  */
     110        5364 : class CRollingBloomFilter
     111             : {
     112             : public:
     113             :     // A random bloom filter calls GetRand() at creation time.
     114             :     // Don't create global CRollingBloomFilter objects, as they may be
     115             :     // constructed before the randomizer is properly initialized.
     116             :     CRollingBloomFilter(unsigned int nElements, double nFPRate);
     117             : 
     118             :     void insert(const std::vector<unsigned char>& vKey);
     119             :     void insert(const uint256& hash);
     120             :     bool contains(const std::vector<unsigned char>& vKey) const;
     121             :     bool contains(const uint256& hash) const;
     122             : 
     123             :     void reset();
     124             : 
     125             : private:
     126             :     int nEntriesPerGeneration;
     127             :     int nEntriesThisGeneration;
     128             :     int nGeneration;
     129             :     std::vector<uint64_t> data;
     130             :     unsigned int nTweak;
     131             :     int nHashFuncs;
     132             : };
     133             : 
     134             : #endif // PIVX_BLOOM_H