forked from cerc-io/plugeth
core: Added new TD strategy which mitigate the risk for selfish mining
Assuming the following scenario where a miner has 15% of all hashing power and the ability to exert a moderate control over the network to the point where if the attacker sees a message A, it can't stop A from propagating, but what it **can** do is send a message B and ensure that most nodes see B before A. The attacker can then selfish mine and augment selfish mining strategy by giving his own blocks an advantage. This change makes the time at which a block is received less relevant and so the level of control an attacker has over the network no longer makes a difference. This change changes the current td algorithm `B_td > C_td` to the new algorithm `B_td > C_td || B_td == C_td && rnd < 0.5`.
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@ -725,14 +725,18 @@ func (self *BlockChain) writeHeader(header *types.Header) error {
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if ptd == nil {
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return ParentError(header.ParentHash)
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}
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td := new(big.Int).Add(header.Difficulty, ptd)
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localTd := self.GetTd(self.currentHeader.Hash())
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externTd := new(big.Int).Add(header.Difficulty, ptd)
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// Make sure no inconsistent state is leaked during insertion
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self.mu.Lock()
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defer self.mu.Unlock()
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// If the total difficulty is higher than our known, add it to the canonical chain
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if td.Cmp(self.GetTd(self.currentHeader.Hash())) > 0 {
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// Second clause in the if statement reduces the vulnerability to selfish mining.
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// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
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if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
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// Delete any canonical number assignments above the new head
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for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
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DeleteCanonicalHash(self.chainDb, i)
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@ -753,7 +757,7 @@ func (self *BlockChain) writeHeader(header *types.Header) error {
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self.currentHeader = types.CopyHeader(header)
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}
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// Irrelevant of the canonical status, write the header itself to the database
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if err := WriteTd(self.chainDb, header.Hash(), td); err != nil {
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if err := WriteTd(self.chainDb, header.Hash(), externTd); err != nil {
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glog.Fatalf("failed to write header total difficulty: %v", err)
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}
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if err := WriteHeader(self.chainDb, header); err != nil {
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@ -1060,14 +1064,18 @@ func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err
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if ptd == nil {
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return NonStatTy, ParentError(block.ParentHash())
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}
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td := new(big.Int).Add(block.Difficulty(), ptd)
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localTd := self.GetTd(self.currentBlock.Hash())
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externTd := new(big.Int).Add(block.Difficulty(), ptd)
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// Make sure no inconsistent state is leaked during insertion
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self.mu.Lock()
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defer self.mu.Unlock()
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// If the total difficulty is higher than our known, add it to the canonical chain
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if td.Cmp(self.GetTd(self.currentBlock.Hash())) > 0 {
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// Second clause in the if statement reduces the vulnerability to selfish mining.
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// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
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if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
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// Reorganize the chain if the parent is not the head block
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if block.ParentHash() != self.currentBlock.Hash() {
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if err := self.reorg(self.currentBlock, block); err != nil {
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@ -1081,7 +1089,7 @@ func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err
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status = SideStatTy
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}
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// Irrelevant of the canonical status, write the block itself to the database
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if err := WriteTd(self.chainDb, block.Hash(), td); err != nil {
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if err := WriteTd(self.chainDb, block.Hash(), externTd); err != nil {
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glog.Fatalf("failed to write block total difficulty: %v", err)
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}
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if err := WriteBlock(self.chainDb, block); err != nil {
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@ -44,6 +44,9 @@ var (
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"TRANSCT__RandomByteAtTheEnd",
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"BLOCK__ZeroByteAtTheEnd",
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"TRANSCT__ZeroByteAtTheEnd",
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"ChainAtoChainB_blockorder2",
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"ChainAtoChainB_blockorder1",
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}
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/* Go client does not support transaction (account) nonces above 2^64. This
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