diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..e27be8d
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "spec"]
+	path = spec
+	url = https://github.com/fernet/spec.git
diff --git a/spec b/spec
new file mode 160000
index 0000000..0250c59
--- /dev/null
+++ b/spec
@@ -0,0 +1 @@
+Subproject commit 0250c594a266036afb39aa574b88d9283810be47