diff --git a/.travis.yml b/.travis.yml
index aa55311..80080c8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@ dist: trusty
 sudo: false
 
 before_install:
-  - pip install --quiet codecov wheel
+  - pip install --quiet codecov wheel cryptography
 
 install:
   - make install
diff --git a/README.rst b/README.rst
index 2200a70..5568404 100644
--- a/README.rst
+++ b/README.rst
@@ -13,7 +13,7 @@ dependency on `cryptography <https://pypi.python.org/pypi/cryptography>`_.
   from requests_http_signature import HTTPSignatureAuth
   preshared_secret = 'monorail_cat'
   url = 'http://httpbin.org/get'
-  requests.get(url, auth=HTTPSignatureAuth(secret=preshared_secret))
+  requests.get(url, auth=HTTPSignatureAuth(key=preshared_secret))
 
 
 Installation
diff --git a/setup.py b/setup.py
index 979aa71..271f070 100755
--- a/setup.py
+++ b/setup.py
@@ -27,5 +27,9 @@ setup(
         'Programming Language :: Python :: 3.4',
         'Development Status :: 5 - Production/Stable',
         'Topic :: Software Development :: Libraries :: Python Modules'
-    ]
+    ],
+    extras_require={
+        "rsa": ["cryptography >= 1.8.2"],
+        "ecdsa": ["cryptography >= 1.8.2"]
+    }
 )