diff --git a/ci-requirements.txt b/ci-requirements.txt
new file mode 100644
index 00000000..76e4a72f
--- /dev/null
+++ b/ci-requirements.txt
@@ -0,0 +1,7 @@
+cryptography
+pynacl
+securesystemslib
+six
+iso8601
+coverage
+coveralls
diff --git a/dev-requirements.txt b/dev-requirements.txt
index a5509f89..fbe53865 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -16,9 +16,11 @@
 # signatures.  The minimal install can only verify ed25519 signatures.  Pinned
 # packages: http://nvie.com/posts/pin-your-packages/
 cffi==1.11.2
+six=1.11.0
+iso8601=0.1.12
 pynacl==1.2.0
 cryptography==2.1.3
-securesystemslib==0.10.7
+securesystemslib==0.10.8
 
 # Testing requirements.  The rest of the testing dependencies available in
 # 'tox.ini'
diff --git a/requirements.txt b/requirements.txt
index 287deaf3..fb0b1f4b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,8 +1,5 @@
 cryptography
 pynacl
-pycrypto
 securesystemslib
 six
 iso8601
-coverage
-coveralls
diff --git a/setup.py b/setup.py
index 03de396b..a8dc181f 100755
--- a/setup.py
+++ b/setup.py
@@ -97,7 +97,6 @@
     'Programming Language :: Python :: 2',
     'Programming Language :: Python :: 2.7',
     'Programming Language :: Python :: 3',
-    'Programming Language :: Python :: 3.3',
     'Programming Language :: Python :: 3.4',
     'Programming Language :: Python :: 3.5',
     'Programming Language :: Python :: 3.6',
@@ -105,7 +104,7 @@
     'Topic :: Security',
     'Topic :: Software Development'
   ],
-   install_requires = ['iso8601', 'six', 'securesystemslib>=0.10.7'],
+   install_requires = ['iso8601>=0.1.12', 'six>=1.11.0', 'securesystemslib>=0.10.8'],
   packages = find_packages(exclude=['tests']),
   scripts = [
     'tuf/scripts/basic_client.py',
diff --git a/tox.ini b/tox.ini
index 55e9d108..c4afbadc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py27, py33, py34, py35, py36
+envlist = py27, py34, py35, py36
 
 [testenv]
 changedir = tests
@@ -12,9 +12,8 @@ changedir = tests
 commands =
     coverage run --source tuf aggregate_tests.py
     coverage report -m --fail-under 97
-    coverage html
 
 deps =
-    -r{toxinidir}/requirements.txt
+    -r{toxinidir}/ci-requirements.txt
 
 install_command = pip install --pre {opts} {packages}