commit inicial do projeto

internal/consensus/finality.go

@@ -0,0 +1,72 @@
+package consensus
+
+import (
+	"crypto/ecdsa"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"math/big"
+	"time"
+
+	"dejo_node/internal/transactions"
+)
+
+// Finalizer encapsula a lógica de selar e assinar blocos.
+type Finalizer struct {
+	PrivateKey *ecdsa.PrivateKey
+	NodeID     string // opcional: ID do produtor do bloco
+}
+
+// Finalize executa a finalização de um bloco:
+// - Adiciona timestamp
+// - Gera hash final
+// - Retorna assinatura
+func (f *Finalizer) Finalize(block *transactions.Block) (string, error) {
+	if block == nil {
+		return "", errors.New("bloco nulo")
+	}
+
+	block.Timestamp = time.Now().Unix()
+
+	// Geração do hash usando campos existentes do bloco
+	hashInput := []byte(
+		fmt.Sprintf("%d|%s|%d|%s",
+			block.Index,
+			block.PrevHash,
+			block.Timestamp,
+			f.NodeID,
+		),
+	)
+	hash := sha256.Sum256(hashInput)
+	block.Hash = hex.EncodeToString(hash[:])
+
+	r, s, err := ecdsa.Sign(rand.Reader, f.PrivateKey, hash[:])
+	if err != nil {
+		return "", err
+	}
+
+	sig := append(r.Bytes(), s.Bytes()...)
+	signature := hex.EncodeToString(sig)
+
+	return signature, nil
+}
+
+// VerifySignature verifica se a assinatura é válida com a chave pública fornecida.
+func VerifySignature(block *transactions.Block, signature string, pubKey *ecdsa.PublicKey) bool {
+	hash, err := hex.DecodeString(block.Hash)
+	if err != nil {
+		return false
+	}
+
+	sig, err := hex.DecodeString(signature)
+	if err != nil || len(sig) < 64 {
+		return false
+	}
+
+	r := big.NewInt(0).SetBytes(sig[:len(sig)/2])
+	s := big.NewInt(0).SetBytes(sig[len(sig)/2:])
+
+	return ecdsa.Verify(pubKey, hash, r, s)
+}