區塊鏈工作量證明及哈希算法
什麽是工作量證明:
1、工作的結果作為數據加入區塊鏈成為一個區塊
2、完成這個工作的人會獲得獎勵(這也就是通過挖礦獲得比特幣)
3、整個“努力工作並進行證明”的機制,就叫工作量證明
為什麽采用哈希算法:
1、不可逆:無法從一個哈希值恢復原始數據,哈希並不是加密
2、唯一性:對於特定的數據,只能有一個哈希值,並且這個哈希值是唯一的
3、防篡改:改變輸入數據中的一個字節,導致輸出一個完全不同的哈希
哈希算法特征:
1、正向快速:給定明文和hash算法,在有限時間和有限資源內能計算出hash值
2、逆向困難:給定hash值,在有限時間內很難逆推出明文
3、輸入敏感:原始輸入信息修改一點信息,產生的hash值會有很大的不同
main.go
package main import ( "core" "fmt" "strconv" ) func main() { bc := core.NewBlockChain() bc.AddBlock("Send 1 BC to Ivan") bc.AddBlock("Send more BC to Ivan") for _,block := range bc.Blocks { fmt.Printf("Prev hash: %x\n", block.PrevBlockHash) fmt.Printf("Data: %s\n", block.Data) fmt.Printf("Hash: %x\n", block.Hash) //創建工作量證明 pow := core.NewProofOfWork(block) //驗證工作量證明 fmt.Printf("Pow: %s\n", strconv.FormatBool(pow.Validate())) fmt.Println() } }
block.go
package core import ( "time" "strconv" "bytes" "crypto/sha256" ) //Block keeps block header type Block struct { Timestamp int64 //區塊創建的時間 Data []byte //區塊包含的數據 PrevBlockHash []byte //前一個區塊的哈希值 Hash []byte //區塊自身的哈希值,用於校驗區塊數據有效 Nonce int //記錄工作量證明用到的數字 } //NewBlock create and returns Block func NewBlock(data string, prevBlockHash []byte) *Block { block := &Block{ Timestamp:time.Now().Unix(), Data: []byte(data), PrevBlockHash: prevBlockHash, Hash: []byte{}, } pow := NewProofOfWork(block) //新建工作量證明 nonce,hash := pow.Run() //執行工作量證明(挖礦) block.Hash = hash block.Nonce = nonce return block } func (b *Block) SetHash() { timestamp := []byte(strconv.FormatInt(b.Timestamp, 10)) headers := bytes.Join([][]byte{b.PrevBlockHash, b.Data, timestamp},[]byte{}) hash := sha256.Sum256(headers) b.Hash = hash[:] } //NewGenesisBlock create and returns genesis Block func NewGenesisBlock() *Block { return NewBlock("Genesis Block", []byte{}) }
proofofwork.go
package core import ( "math" "math/big" "fmt" "crypto/sha256" "bytes" ) var ( maxNonce = math.MaxInt64 ) const targetBits = 20 //ProofOfWork represents a proof-of-work type ProofOfWork struct { block *Block target *big.Int } //NewProofOfWork builds and returns a ProofOfWork func NewProofOfWork(b *Block) *ProofOfWork { target := big.NewInt(1) target.Lsh(target,uint(256-targetBits)) pow := &ProofOfWork{b, target} return pow } func (pow *ProofOfWork) prepareData(nonce int) []byte { data := bytes.Join( [][]byte{ pow.block.PrevBlockHash, pow.block.Data, IntToHex(int64(pow.block.Timestamp)), IntToHex(int64(nonce)), }, []byte{}, ) return data } func (pow *ProofOfWork) Run() (int, []byte) { var hashInt big.Int var hash [32]byte nonce := 0 fmt.Printf("Mining the block containing \"%s\"\n", pow.block.Data) for nonce < maxNonce { data := pow.prepareData(nonce) hash = sha256.Sum256(data) fmt.Printf("\r%x", hash) hashInt.SetBytes(hash[:]) if hashInt.Cmp(pow.target) == -1 { break }else{ nonce++ } } fmt.Print("\n\n") return nonce,hash[:] } func (pow *ProofOfWork) Validate() bool { var hashInt big.Int data := pow.prepareData(pow.block.Nonce) hash := sha256.Sum256(data) hashInt.SetBytes(hash[:]) isValid := hashInt.Cmp(pow.target) == -1 return isValid }
utils.go
package core import ( "bytes" "encoding/binary" "log" ) func IntToHex(num int64) []byte { buff := new(bytes.Buffer) err := binary.Write(buff, binary.BigEndian, num) if err != nil { log.Panic(err) } return buff.Bytes() }
打印結果:
Mining the block containing "Genesis Block"
00000965faabec60c056cc30d9e6e45a0db7cfa84cb5897d8d5bdaa96971bd5f
Mining the block containing "Send 1 BC to Ivan"
000006910ca6331d7c640787defe1189fb158bc3d624949bc61b68a3f0031efc
Mining the block containing "Send more BC to Ivan"
00000a9e4f7f891bf6dd7323a1a5b698d5ba88c9363c8f5c9676fd075d526796
Prev hash:
Data: Genesis Block
Hash: 00000965faabec60c056cc30d9e6e45a0db7cfa84cb5897d8d5bdaa96971bd5f
Pow: true
Prev hash: 00000965faabec60c056cc30d9e6e45a0db7cfa84cb5897d8d5bdaa96971bd5f
Data: Send 1 BC to Ivan
Hash: 000006910ca6331d7c640787defe1189fb158bc3d624949bc61b68a3f0031efc
Pow: true
Prev hash: 000006910ca6331d7c640787defe1189fb158bc3d624949bc61b68a3f0031efc
Data: Send more BC to Ivan
Hash: 00000a9e4f7f891bf6dd7323a1a5b698d5ba88c9363c8f5c9676fd075d526796
Pow: true
區塊鏈工作量證明及哈希算法