diff --git a/interface/include/tfm_attest_defs.h b/interface/include/tfm_attest_defs.h
new file mode 100644
index 0000000..dad7769
--- /dev/null
+++ b/interface/include/tfm_attest_defs.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef __TFM_ATTEST_DEFS_H__
+#define __TFM_ATTEST_DEFS_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Initial Attestation message types that distinguish Attest services. */
+#define TFM_ATTEST_GET_TOKEN       1001
+#define TFM_ATTEST_GET_TOKEN_SIZE  1002
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __TFM_ATTEST_DEFS_H__ */