pos介绍

参考链接1

pos概念

Proof of Stake，股权证明。
PoS核心概念为币龄，即持有货币的时间。例如有10个币、持有90天，即拥有900币天的币龄。
另外使用币，即意味着币龄的销毁。
在PoS中有一种特殊的交易称为利息币，即持有人可以消耗币龄获得利息，同时获得为网络产生区块、以及PoS造币的优先权。

点点币应用

第一个基于PoS的虚拟币是点点币。鉴于PoW的缺陷，2012年Sunny King提出了PoS，并基于PoW和PoS的混合机制发布了点点币PPCoin。前期采用PoW挖矿开采和分配货币，以保证公平。后期采用PoS机制，保障网络安全，即拥有51%货币难度更大，从而防止51%攻击。

点点币（Peercoin）是首先采用权益证明的货币，点点币在SHA256的哈希运算的难度方面引入了币龄的概念，使得难度与交易输入的币龄成反比。在点点币中，币龄被定义为币的数量与币所拥有的天数的乘积，这使得币龄能够反映交易时刻用户所拥有的货币数量。实际上，点点币的权益证明机制结合了随机化与币龄的概念，未使用至少30天的币可以参与竞争下一区块，越久和越大的币集有更大的可能去签名下一区块。

然而，一旦币的权益被用于签名一个区块，则币龄将清为零，这样必须等待至少30日才能签署另一区块。同时，为防止非常老或非常大的权益控制区块链，寻找下一区块的最大概率在90天后达到最大值，这一过程保护了网络，并随着时间逐渐生成新的币而无需消耗大量的计算能力。点点币的开发者声称这将使得恶意攻击变得困难，因为没有中心化的挖矿池需求，而且购买半数以上的币的开销似乎超过获得51%的工作量证明的哈希计算能力。

优缺点

• 优点： 缩短了共识达成的时间，链中共识块的速度更快，不再需要大量消耗能源挖矿。作弊得不尝失，因为如果一名持有 51% 以上股权的人作弊，相当于他坑了自己，因为他是拥有股权最多的人，作弊导致的结果往往是拥有着越多的损失越多。
• 缺点： 攻击成本低，只有节点有物品数量，例如代币数量，就能发起脏数据的区块攻击，另外拥有代币数量大的节点获得记账权的概率会更大，会使得网络共识受少数富裕账户支配，从而失去公正性。

go实现pos算法

csdn
腾讯云
简书
.env

PORT=9000

main.go

package main

import (
    "bufio"
    "crypto/sha256"
    "encoding/hex"
    "encoding/json"
    "fmt"
    "io"
    "log"
    "math/rand"
    "net"
    "os"
    "strconv"
    "sync"
    "time"

    "github.com/davecgh/go-spew/spew"
    "github.com/joho/godotenv"
)

// Block represents each 'item' in the blockchain
type Block struct {
    Index     int
    Timestamp string
    BPM       int
    Hash      string
    PrevHash  string
    Validator string
}

var Blockchain []Block // Blockchain is a series of validated Blocks
var tempBlocks []Block // tempBlocks是临时存储单元，在区块被选出来并添加到BlockChain之前，临时存储在这里

// candidateBlocks handles incoming blocks for validation
var candidateBlocks = make(chan Block)

// announcements broadcasts winning validator to all nodes
var announcements = make(chan string)

var mutex = &sync.Mutex{}

// validators keeps track of open validators and balances
var validators = make(map[string]int)

func main() {

    err := godotenv.Load("./test/example.env")
    if err != nil {
        log.Fatal(err)
    }

    // create genesis block
    t := time.Now()
    genesisBlock := Block{}
    genesisBlock = Block{0, t.String(), 0, calculateBlockHash(genesisBlock), "", ""}
    spew.Dump(genesisBlock)
    Blockchain = append(Blockchain, genesisBlock)

    httpPort := os.Getenv("PORT")

    // start TCP and serve TCP server
    server, err := net.Listen("tcp", ":"+httpPort)
    if err != nil {
        log.Fatal(err)
    }
    log.Println("HTTP Server Listening on port :", httpPort)
    defer server.Close()

    go func() {
        for candidate := range candidateBlocks {
            mutex.Lock()
            tempBlocks = append(tempBlocks, candidate)
            mutex.Unlock()
        }
    }()

    go func() {
        for {
            pickWinner()
        }
    }()

    for {
        conn, err := server.Accept()
        if err != nil {
            log.Fatal(err)
        }
        go handleConn(conn)
    }
}

// pickWinner creates a lottery pool of validators and chooses the validator who gets to forge a block to the blockchain
// by random selecting from the pool, weighted by amount of tokens staked
func pickWinner() {
    time.Sleep(30 * time.Second)
    mutex.Lock()
    temp := tempBlocks
    mutex.Unlock()

    lotteryPool := []string{}
    if len(temp) > 0 {

        // slightly modified traditional proof of stake algorithm
        // from all validators who submitted a block, weight them by the number of staked tokens
        // in traditional proof of stake, validators can participate without submitting a block to be forged
    OUTER:
        for _, block := range temp {
            // if already in lottery pool, skip
            for _, node := range lotteryPool {
                if block.Validator == node {
                    continue OUTER
                }
            }

            // lock list of validators to prevent data race
            mutex.Lock()
            setValidators := validators
            mutex.Unlock()

            k, ok := setValidators[block.Validator]
            if ok {
                for i := 0; i < k; i++ {
                    lotteryPool = append(lotteryPool, block.Validator)
                }
            }
        }

        // randomly pick winner from lottery pool
        s := rand.NewSource(time.Now().Unix())
        r := rand.New(s)
        lotteryWinner := lotteryPool[r.Intn(len(lotteryPool))]

        // add block of winner to blockchain and let all the other nodes know
        for _, block := range temp {
            if block.Validator == lotteryWinner {
                mutex.Lock()
                Blockchain = append(Blockchain, block)
                mutex.Unlock()
                for _ = range validators {
                    announcements <- "\nwinning validator: " + lotteryWinner + "\n"
                }
                break
            }
        }
    }

    mutex.Lock()
    tempBlocks = []Block{}
    mutex.Unlock()
}

func handleConn(conn net.Conn) {
    defer conn.Close()

    go func() {
        for {
            msg := <-announcements
            io.WriteString(conn, msg)
        }
    }()
    // validator address
    var address string

    // tokens数量由用户从控制台输入
    io.WriteString(conn, "Enter token balance:")
    scanBalance := bufio.NewScanner(conn)
    // 获取用户输入的balance值，并打印出来
    for scanBalance.Scan() {
        balance, err := strconv.Atoi(scanBalance.Text())
        if err != nil {
            log.Printf("%v not a number: %v", scanBalance.Text(), err)
            return
        }
        t := time.Now()
        address = calculateHash(t.String())
        validators[address] = balance
        fmt.Println(validators)
        break // 只循环一次
    }

    // 循环输入BPM
    io.WriteString(conn, "\nEnter a new BPM:")

    scanBPM := bufio.NewScanner(conn)

    go func() {
        for {
            // take in BPM from stdin and add it to blockchain after conducting necessary validation
            for scanBPM.Scan() {
                bpm, err := strconv.Atoi(scanBPM.Text())
                // if malicious party tries to mutate the chain with a bad input, delete them as a validator and they lose their staked tokens
                if err != nil {
                    log.Printf("%v not a number: %v", scanBPM.Text(), err)
                    delete(validators, address)
                    conn.Close()
                }

                mutex.Lock()
                oldLastIndex := Blockchain[len(Blockchain)-1]
                mutex.Unlock()

                // 生成新的区块
                newBlock, err := generateBlock(oldLastIndex, bpm, address)
                if err != nil {
                    log.Println(err)
                    continue
                }
                if isBlockValid(newBlock, oldLastIndex) {
                    // main func 中 for candidate := range candidateBlocks ,将newBlock 追加到 tempBlocks中
                    candidateBlocks <- newBlock
                }
                io.WriteString(conn, "\nEnter a new BPM:")
            }
        }
    }()

    // simulate receiving broadcast
    for {
        time.Sleep(time.Minute)
        mutex.Lock()
        output, err := json.Marshal(Blockchain)
        mutex.Unlock()
        if err != nil {
            log.Fatal(err)
        }
        io.WriteString(conn, string(output)+"\n")
    }

}

// isBlockValid makes sure block is valid by checking index
// and comparing the hash of the previous block
func isBlockValid(newBlock, oldBlock Block) bool {
    if oldBlock.Index+1 != newBlock.Index {
        return false
    }

    if oldBlock.Hash != newBlock.PrevHash {
        return false
    }

    if calculateBlockHash(newBlock) != newBlock.Hash {
        return false
    }

    return true
}

// SHA256 hasing
// calculateHash is a simple SHA256 hashing function
func calculateHash(s string) string {
    h := sha256.New()
    h.Write([]byte(s))
    hashed := h.Sum(nil)
    return hex.EncodeToString(hashed)
}

//calculateBlockHash returns the hash of all block information
func calculateBlockHash(block Block) string {
    record := string(block.Index) + block.Timestamp + string(block.BPM) + block.PrevHash
    return calculateHash(record)
}

// generateBlock creates a new block using previous block's hash
func generateBlock(oldBlock Block, BPM int, address string) (Block, error) {

    var newBlock Block

    t := time.Now()

    newBlock.Index = oldBlock.Index + 1
    newBlock.Timestamp = t.String()
    newBlock.BPM = BPM
    newBlock.PrevHash = oldBlock.Hash
    newBlock.Hash = calculateBlockHash(newBlock)
    newBlock.Validator = address

    return newBlock, nil
}