#5 Uses persistent storage only

mino/minows/key/mod.go

@@ -1,19 +1,63 @@
 package key
 
 import (
+	"crypto/rand"
 	"github.com/libp2p/go-libp2p/core/crypto"
 	"go.dedis.ch/dela/core/store/kv"
+	"golang.org/x/xerrors"
 )
 
-// Storage is an interface for storing and retrieving private keys.
-type Storage interface {
-	// LoadOrCreate loads the private key associated with a mino instance.
-	// If the key does not exist, it will create a new one.
-	LoadOrCreate() (crypto.PrivKey, error)
+// Storage provides persistent Storage for private keys.
+type Storage struct {
+	bucket []byte
+	db     kv.DB
 }
 
-// NewStorage creates a new private key storage
-// with caching for efficient access.
-func NewStorage(db kv.DB) Storage {
-	return newMemoryStore(db)
+// NewStorage creates a new Storage for private keys.
+func NewStorage(db kv.DB) *Storage {
+	return &Storage{
+		bucket: []byte("keys"),
+		db:     db,
+	}
+}
+
+// LoadOrCreate loads the private key from Storage or
+// creates a new one if none exists.
+func (s *Storage) LoadOrCreate() (crypto.PrivKey, error) {
+	key := []byte("private_key")
+	var buffer []byte
+	err := s.db.Update(func(tx kv.WritableTx) error {
+		bucket, err := tx.GetBucketOrCreate(s.bucket)
+		if err != nil {
+			return xerrors.Errorf("could not get bucket: %v", err)
+		}
+
+		bytes := bucket.Get(key)
+		if bytes == nil {
+			private, _, err := crypto.GenerateEd25519Key(rand.Reader)
+			if err != nil {
+				return xerrors.Errorf("could not generate key: %v", err)
+			}
+			bytes, err = crypto.MarshalPrivateKey(private)
+			if err != nil {
+				return xerrors.Errorf("could not marshal key: %v", err)
+			}
+			err = bucket.Set(key, bytes)
+			if err != nil {
+				return xerrors.Errorf("could not store key: %v", err)
+			}
+		}
+		buffer = make([]byte, len(bytes))
+		copy(buffer, bytes)
+		return nil
+	})
+	if err != nil {
+		return nil, xerrors.Errorf("could not update db: %v", err)
+	}
+
+	private, err := crypto.UnmarshalPrivateKey(buffer)
+	if err != nil {
+		return nil, xerrors.Errorf("could not unmarshal key: %v", err)
+	}
+	return private, nil
 }