diff --git a/lib/hci.h b/lib/hci.h
index 48692fa..7f68ea0 100644
--- a/lib/hci.h
+++ b/lib/hci.h
#define HCI_LM_RELIABLE 0x0010
#define HCI_LM_SECURE 0x0020
+/* Link Key types */
+#define HCI_LK_COMBINATION 0x00
+#define HCI_LK_LOCAL_UNIT 0x01
+#define HCI_LK_REMOTE_UNIT 0x02
+#define HCI_LK_DEBUG_COMBINATION 0x03
+#define HCI_LK_UNAUTH_COMBINATION 0x04
+#define HCI_LK_AUTH_COMBINATION 0x05
+#define HCI_LK_CHANGED_COMBINATION 0x06
+#define HCI_LK_INVALID 0xFF
+
/* ----- HCI Commands ----- */
/* Link Control */