98 lines
1.5 KiB
Go
98 lines
1.5 KiB
Go
package blockchain
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import (
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"bytes"
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"crypto/sha256"
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"encoding/binary"
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"fmt"
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"log"
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"math"
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"math/big"
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)
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// Take the data from the block
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// Create a counter (nonce) which starts at 0
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// Create a hash of the data plus the counter
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// Check the hash to see if it meets a set of requireents
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// Requirements:
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// The first few bytes must contain 0s
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const Difficulty = 18
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type ProofOfWork struct {
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Block *Block
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Target *big.Int
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}
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func NewProof(b *Block) *ProofOfWork {
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target := big.NewInt(1)
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target.Lsh(target, uint(256-Difficulty))
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pow := &ProofOfWork{b, target}
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return pow
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}
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func (pow *ProofOfWork) InitData(nonce int) []byte {
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data := bytes.Join(
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[][]byte{
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pow.Block.PrevHash,
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pow.Block.Data,
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ToHex(int64(nonce)),
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ToHex(int64(Difficulty)),
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},
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[]byte{},
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)
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return data
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}
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func (pow *ProofOfWork) Run() (int, []byte) {
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var intHash big.Int
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var hash [32]byte
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nonce := 0
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for nonce < math.MaxInt64 {
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data := pow.InitData(nonce)
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hash = sha256.Sum256(data)
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fmt.Printf("\r%x", hash)
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intHash.SetBytes(hash[:])
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if intHash.Cmp(pow.Target) == -1 {
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break
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} else {
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nonce++
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}
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}
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fmt.Println()
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return nonce, hash[:]
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}
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func (pow *ProofOfWork) Validate() bool {
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var intHash big.Int
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data := pow.InitData(pow.Block.Nonce)
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hash := sha256.Sum256(data)
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intHash.SetBytes(hash[:])
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return intHash.Cmp(pow.Target) == -1
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}
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func ToHex(num int64) []byte {
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buff := new(bytes.Buffer)
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err := binary.Write(buff, binary.BigEndian, num)
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if err != nil {
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log.Panic(err)
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}
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return buff.Bytes()
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}
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