diff --git a/requirements.txt b/requirements.txt
index c71cabe..bc8358b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,7 @@
 jsonschema>=3.2.0 # MIT
 testtools>=2.2.0 # MIT
 paramiko>=2.7.0 # LGPLv2.1+
+cryptography>=2.1 # BSD/Apache-2.0
 netaddr>=0.7.18 # BSD
 oslo.concurrency>=3.26.0 # Apache-2.0
 oslo.config>=5.2.0 # Apache-2.0