Made it a bit cleaner :)

pkg/engine/keys.go

@@ -0,0 +1,35 @@
+package engine
+
+import (
+	"crypto/ecdh"
+	"encoding/hex"
+)
+
+type KeyPair struct {
+	PrivateKey *ecdh.PrivateKey
+	PublicKey  *ecdh.PublicKey
+}
+
+func (kp *KeyPair) EncodePublicKey() string {
+	return hex.EncodeToString(kp.PublicKey.Bytes())
+}
+
+func (kp *KeyPair) EncodePrivateKey() string {
+	return hex.EncodeToString(kp.PrivateKey.Bytes())
+}
+
+func (e *Engine) DecodePrivateKey(hexKey string) (*ecdh.PrivateKey, error) {
+	bytes, err := hex.DecodeString(hexKey)
+	if err != nil {
+		return nil, err
+	}
+	return e.curve.NewPrivateKey(bytes)
+}
+
+func (e *Engine) DecodePublicKey(hexKey string) (*ecdh.PublicKey, error) {
+	bytes, err := hex.DecodeString(hexKey)
+	if err != nil {
+		return nil, err
+	}
+	return e.curve.NewPublicKey(bytes)
+}