make the protocol package internal

internal/protocol/encryption_level.go

@@ -0,0 +1,28 @@
+package protocol
+
+// EncryptionLevel is the encryption level
+// Default value is Unencrypted
+type EncryptionLevel int
+
+const (
+	// EncryptionUnspecified is a not specified encryption level
+	EncryptionUnspecified EncryptionLevel = iota
+	// EncryptionUnencrypted is not encrypted
+	EncryptionUnencrypted
+	// EncryptionSecure is encrypted, but not forward secure
+	EncryptionSecure
+	// EncryptionForwardSecure is forward secure
+	EncryptionForwardSecure
+)
+
+func (e EncryptionLevel) String() string {
+	switch e {
+	case EncryptionUnencrypted:
+		return "unencrypted"
+	case EncryptionSecure:
+		return "encrypted (not forward-secure)"
+	case EncryptionForwardSecure:
+		return "forward-secure"
+	}
+	return "unknown"
+}