blockchain sandbox: UTXO chain, p2p mining, attacker node

chain/block.go

@@ -0,0 +1,47 @@
+package chain
+
+import (
+	"blockchain/config"
+	"crypto/sha256"
+	"encoding/hex"
+	"strconv"
+	"strings"
+)
+
+type Block struct {
+	Height       int
+	Transactions []*Transaction
+	PrevHash     string
+	Hash         string
+	Nonce        int
+}
+
+func NewBlock(height int, txs []*Transaction, prevHash string) *Block {
+	return &Block{
+		Height:       height,
+		Transactions: txs,
+		PrevHash:     prevHash,
+	}
+}
+
+// HashBase returns the pre-computed prefix for nonce iteration.
+func (b *Block) HashBase() string {
+	var sb strings.Builder
+	sb.WriteString(strconv.Itoa(b.Height))
+	for _, tx := range b.Transactions {
+		sb.WriteString(tx.TxID())
+	}
+	sb.WriteString(b.PrevHash)
+	return sb.String()
+}
+
+func (b *Block) CalcHash() string {
+	data := b.HashBase() + strconv.Itoa(b.Nonce)
+	hash := sha256.Sum256([]byte(data))
+	return hex.EncodeToString(hash[:])
+}
+
+func (b *Block) CheckProofOfWork() bool {
+	prefix := strings.Repeat("0", config.Default.Chain.Difficulty)
+	return b.Hash == b.CalcHash() && strings.HasPrefix(b.Hash, prefix)
+}