diff --git a/AUTHORS.rst b/AUTHORS.rst
index e9c2f85..c06faf1 100644
--- a/AUTHORS.rst
+++ b/AUTHORS.rst
@@ -15,3 +15,4 @@
 * Konstantinos Koukopoulos <koukopoulos@gmail.com> (D6BD 52B6 8C99 A91C E2C8  934D 3300 566B 3A46 726E)
 * Stephen Holsapple <sholsapp@gmail.com>
 * Terry Chia <terrycwk1994@gmail.com>
+* Matthew Iversen <matt@notevencode.com> (2F04 3DCC D6E6 D5AC D262  2E0B C046 E8A8 7452 2973)
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
new file mode 100644
index 0000000..bbbcfb1
--- /dev/null
+++ b/CHANGELOG.rst
@@ -0,0 +1,35 @@
+Changelog
+=========
+
+0.3 - 2014-XX-XX
+~~~~~~~~~~~~~~~~
+
+* Added :class:`~cryptography.hazmat.primitives.twofactor.hotp.HOTP`.
+* Added :class:`~cryptography.hazmat.primitives.twofactor.totp.TOTP`.
+
+0.2.1 - 2014-02-22
+~~~~~~~~~~~~~~~~~~
+* Fix a bug where importing cryptography from multiple paths could cause initialization to fail.
+
+0.2 - 2014-02-20
+~~~~~~~~~~~~~~~~
+
+* Added :doc:`/hazmat/backends/commoncrypto`.
+* Added initial :doc:`/hazmat/bindings/commoncrypto`.
+* Removed ``register_cipher_adapter`` method from
+  :class:`~cryptography.hazmat.backends.interfaces.CipherBackend`.
+* Added support for the OpenSSL backend under Windows.
+* Improved thread-safety for the OpenSSL backend.
+* Fixed compilation on systems where OpenSSL's ``ec.h`` header is not
+  available, such as CentOS.
+* Added :class:`~cryptography.hazmat.primitives.kdf.pbkdf2.PBKDF2HMAC`.
+* Added :class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF`.
+* Added :doc:`/hazmat/backends/multibackend`.
+* Set default random for the :doc:`/hazmat/backends/openssl` to the OS random engine.
+* Added :class:`~cryptography.hazmat.primitives.ciphers.algorithms.CAST5` (CAST-128) support.
+
+0.1 - 2014-01-08
+~~~~~~~~~~~~~~~~
+
+* Initial release.
+
diff --git a/MANIFEST.in b/MANIFEST.in
index c5ca035..a252cc8 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,8 +1,11 @@
-include LICENSE
 include AUTHORS.rst
+include CHANGELOG.rst
 include CONTRIBUTING.rst
+include LICENSE
 include README.rst
 
+recursive-include docs *
+prune docs/_build
 recursive-include tests *.py
 recursive-include tests/vectors *
 recursive-include tests/hazmat/primitives/vectors *
diff --git a/cryptography/hazmat/bindings/openssl/ssl.py b/cryptography/hazmat/bindings/openssl/ssl.py
index ca3e96c..25e4967 100644
--- a/cryptography/hazmat/bindings/openssl/ssl.py
+++ b/cryptography/hazmat/bindings/openssl/ssl.py
@@ -136,6 +136,7 @@
 typedef struct {
     SSL3_STATE *s3;
     SSL_SESSION *session;
+    int type;
     ...;
 } SSL;
 
@@ -219,6 +220,9 @@
 const char *SSL_CIPHER_get_name(const SSL_CIPHER *);
 int SSL_CIPHER_get_bits(const SSL_CIPHER *, int *);
 char *SSL_CIPHER_get_version(const SSL_CIPHER *);
+
+size_t SSL_get_finished(const SSL *, void *, size_t);
+size_t SSL_get_peer_finished(const SSL *, void *, size_t);
 """
 
 MACROS = """
@@ -298,6 +302,8 @@
 void SSL_CTX_set_tlsext_servername_callback(
     SSL_CTX *,
     int (*)(const SSL *, int *, void *));
+
+long SSL_session_reused(SSL *);
 """
 
 CUSTOMIZATIONS = """
diff --git a/cryptography/hazmat/primitives/asymmetric/rsa.py b/cryptography/hazmat/primitives/asymmetric/rsa.py
index a63d430..2f9e424 100644
--- a/cryptography/hazmat/primitives/asymmetric/rsa.py
+++ b/cryptography/hazmat/primitives/asymmetric/rsa.py
@@ -132,7 +132,7 @@
         self._modulus = modulus
 
     @classmethod
-    def generate(self, public_exponent, key_size, backend):
+    def generate(cls, public_exponent, key_size, backend):
         return backend.generate_rsa_private_key(public_exponent, key_size)
 
     def signer(self, padding, algorithm, backend):
diff --git a/cryptography/hazmat/primitives/twofactor/hotp.py b/cryptography/hazmat/primitives/twofactor/hotp.py
index 535a94c..24f5f46 100644
--- a/cryptography/hazmat/primitives/twofactor/hotp.py
+++ b/cryptography/hazmat/primitives/twofactor/hotp.py
@@ -17,27 +17,31 @@
 
 import six
 
-from cryptography.exceptions import InvalidToken
+from cryptography.exceptions import InvalidToken, UnsupportedAlgorithm
 from cryptography.hazmat.primitives import constant_time, hmac
-from cryptography.hazmat.primitives.hashes import SHA1
+from cryptography.hazmat.primitives.hashes import SHA1, SHA256, SHA512
 
 
 class HOTP(object):
-    def __init__(self, key, length, backend):
-
+    def __init__(self, key, length, algorithm, backend):
         if len(key) < 16:
             raise ValueError("Key length has to be at least 128 bits.")
 
         if length < 6 or length > 8:
             raise ValueError("Length of HOTP has to be between 6 to 8.")
 
+        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
+            raise UnsupportedAlgorithm(
+                "Algorithm must be SHA1, SHA256 or SHA512")
+
         self._key = key
         self._length = length
+        self._algorithm = algorithm
         self._backend = backend
 
     def generate(self, counter):
         truncated_value = self._dynamic_truncate(counter)
-        hotp = truncated_value % (10**self._length)
+        hotp = truncated_value % (10 ** self._length)
         return "{0:0{1}}".format(hotp, self._length).encode()
 
     def verify(self, hotp, counter):
@@ -45,12 +49,12 @@
             raise InvalidToken("Supplied HOTP value does not match")
 
     def _dynamic_truncate(self, counter):
-        ctx = hmac.HMAC(self._key, SHA1(), self._backend)
+        ctx = hmac.HMAC(self._key, self._algorithm, self._backend)
         ctx.update(struct.pack(">Q", counter))
         hmac_value = ctx.finalize()
 
-        offset_bits = six.indexbytes(hmac_value, 19) & 0b1111
+        offset_bits = six.indexbytes(hmac_value, len(hmac_value) - 1) & 0b1111
 
         offset = int(offset_bits)
-        P = hmac_value[offset:offset+4]
-        return struct.unpack(">I", P)[0] & 0x7fffffff
+        p = hmac_value[offset:offset + 4]
+        return struct.unpack(">I", p)[0] & 0x7fffffff
diff --git a/cryptography/hazmat/primitives/twofactor/totp.py b/cryptography/hazmat/primitives/twofactor/totp.py
new file mode 100644
index 0000000..0630de6
--- /dev/null
+++ b/cryptography/hazmat/primitives/twofactor/totp.py
@@ -0,0 +1,32 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import, division, print_function
+
+from cryptography.exceptions import InvalidToken
+from cryptography.hazmat.primitives import constant_time
+from cryptography.hazmat.primitives.twofactor.hotp import HOTP
+
+
+class TOTP(object):
+    def __init__(self, key, length, algorithm, time_step, backend):
+        self._time_step = time_step
+        self._hotp = HOTP(key, length, algorithm, backend)
+
+    def generate(self, time):
+        counter = int(time / self._time_step)
+        return self._hotp.generate(counter)
+
+    def verify(self, totp, time):
+        if not constant_time.bytes_eq(self.generate(time), totp):
+            raise InvalidToken("Supplied TOTP value does not match")
diff --git a/docs/changelog.rst b/docs/changelog.rst
index b87b872..565b052 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,34 +1 @@
-Changelog
-=========
-
-0.3 - 2014-XX-XX
-~~~~~~~~~~~~~~~~
-
-* Added :class:`~cryptography.hazmat.primitives.twofactor.hotp.HOTP`.
-
-0.2.1 - 2014-02-22
-~~~~~~~~~~~~~~~~~~
-* Fix a bug where importing cryptography from multiple paths could cause initialization to fail.
-
-0.2 - 2014-02-20
-~~~~~~~~~~~~~~~~
-
-* Added :doc:`/hazmat/backends/commoncrypto`.
-* Added initial :doc:`/hazmat/bindings/commoncrypto`.
-* Removed ``register_cipher_adapter`` method from
-  :class:`~cryptography.hazmat.backends.interfaces.CipherBackend`.
-* Added support for the OpenSSL backend under Windows.
-* Improved thread-safety for the OpenSSL backend.
-* Fixed compilation on systems where OpenSSL's ``ec.h`` header is not
-  available, such as CentOS.
-* Added :class:`~cryptography.hazmat.primitives.kdf.pbkdf2.PBKDF2HMAC`.
-* Added :class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF`.
-* Added :doc:`/hazmat/backends/multibackend`.
-* Set default random for the :doc:`/hazmat/backends/openssl` to the OS random engine.
-* Added :class:`~cryptography.hazmat.primitives.ciphers.algorithms.CAST5` (CAST-128) support.
-
-0.1 - 2014-01-08
-~~~~~~~~~~~~~~~~
-
-* Initial release.
-
+.. include:: ../CHANGELOG.rst
diff --git a/docs/development/submitting-patches.rst b/docs/development/submitting-patches.rst
index 5dca3f7..1797b9c 100644
--- a/docs/development/submitting-patches.rst
+++ b/docs/development/submitting-patches.rst
@@ -15,7 +15,10 @@
 Code
 ----
 
-When in doubt, refer to :pep:`8` for Python code.
+When in doubt, refer to :pep:`8` for Python code. You can check if your code
+meets our automated requirements by running ``flake8`` against it. If you've
+installed the development requirements this will automatically use our
+configuration. You can also run the ``tox`` job with ``tox -e pep8``.
 
 `Write comments as complete sentences.`_
 
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index d91dde9..2306c5b 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -88,7 +88,7 @@
     choice for encryption.
 
     :param bytes key: The secret key, either ``128``, ``192``, or ``256`` bits.
-                      This must be kept secret.
+        This must be kept secret.
 
 .. class:: Camellia(key)
 
@@ -97,7 +97,7 @@
     is not as widely studied or deployed.
 
     :param bytes key: The secret key, either ``128``, ``192``, or ``256`` bits.
-                      This must be kept secret.
+        This must be kept secret.
 
 .. class:: TripleDES(key)
 
@@ -108,12 +108,11 @@
     is incredibly slow; old applications should consider moving away from it.
 
     :param bytes key: The secret key, either ``64``, ``128``, or ``192`` bits
-                      (note that DES functionally uses ``56``, ``112``, or
-                      ``168`` bits of the key, there is a parity byte in each
-                      component of the key), in some materials these are
-                      referred to as being up to three separate keys (each
-                      ``56`` bits long), they can simply be concatenated to
-                      produce the full key. This must be kept secret.
+        (note that DES functionally uses ``56``, ``112``, or ``168`` bits of
+        the key, there is a parity byte in each component of the key), in some
+        materials these are referred to as being up to three separate keys
+        (each ``56`` bits long), they can simply be concatenated to produce the
+        full key. This must be kept secret.
 
 .. class:: CAST5(key)
 
@@ -124,7 +123,7 @@
     a variable key length cipher and supports keys from 40-128 bits in length.
 
     :param bytes key: The secret key, 40-128 bits in length (in increments of
-                      8).  This must be kept secret.
+        8).  This must be kept secret.
 
 Weak Ciphers
 ------------
@@ -142,7 +141,7 @@
     that users of Blowfish move to newer algorithms, such as :class:`AES`.
 
     :param bytes key: The secret key, 32-448 bits in length (in increments of
-                      8).  This must be kept secret.
+        8).  This must be kept secret.
 
 .. class:: ARC4(key)
 
@@ -151,8 +150,7 @@
     mode constructions.
 
     :param bytes key: The secret key, ``40``, ``56``, ``64``, ``80``, ``128``,
-                      ``192``, or ``256`` bits in length.  This must be kept
-                      secret.
+        ``192``, or ``256`` bits in length.  This must be kept secret.
 
     .. doctest::
 
@@ -182,17 +180,12 @@
     **Padding is required when using this mode.**
 
     :param bytes initialization_vector: Must be random bytes. They do not need
-                                        to be kept secret (they can be included
-                                        in a transmitted message). Must be the
-                                        same number of bytes as the
-                                        ``block_size`` of the cipher. Each time
-                                        something is encrypted a new
-                                        ``initialization_vector`` should be
-                                        generated. Do not reuse an
-                                        ``initialization_vector`` with
-                                        a given ``key``, and particularly do
-                                        not use a constant
-                                        ``initialization_vector``.
+        to be kept secret (they can be included in a transmitted message). Must
+        be the same number of bytes as the ``block_size`` of the cipher. Each
+        time something is encrypted a new ``initialization_vector`` should be
+        generated. Do not reuse an ``initialization_vector`` with a given
+        ``key``, and particularly do not use a constant
+        ``initialization_vector``.
 
     A good construction looks like:
 
@@ -226,12 +219,11 @@
     **This mode does not require padding.**
 
     :param bytes nonce: Should be random bytes. It is critical to never reuse a
-                        ``nonce`` with a given key.  Any reuse of a nonce
-                        with the same key compromises the security of every
-                        message encrypted with that key. Must be the same
-                        number of bytes as the ``block_size`` of the cipher
-                        with a given key. The nonce does not need to be kept
-                        secret and may be included alongside the ciphertext.
+        ``nonce`` with a given key.  Any reuse of a nonce with the same key
+        compromises the security of every message encrypted with that key. Must
+        be the same number of bytes as the ``block_size`` of the cipher with a
+        given key. The nonce does not need to be kept secret and may be
+        included alongside the ciphertext.
 
 .. class:: OFB(initialization_vector)
 
@@ -241,12 +233,9 @@
     **This mode does not require padding.**
 
     :param bytes initialization_vector: Must be random bytes. They do not need
-                                        to be kept secret (they can be included
-                                        in a transmitted message). Must be the
-                                        same number of bytes as the
-                                        ``block_size`` of the cipher. Do not
-                                        reuse an ``initialization_vector`` with
-                                        a given ``key``.
+        to be kept secret (they can be included in a transmitted message). Must
+        be the same number of bytes as the ``block_size`` of the cipher. Do not
+        reuse an ``initialization_vector`` with a given ``key``.
 
 .. class:: CFB(initialization_vector)
 
@@ -256,12 +245,9 @@
     **This mode does not require padding.**
 
     :param bytes initialization_vector: Must be random bytes. They do not need
-                                        to be kept secret (they can be included
-                                        in a transmitted message). Must be the
-                                        same number of bytes as the
-                                        ``block_size`` of the cipher. Do not
-                                        reuse an ``initialization_vector`` with
-                                        a given ``key``.
+        to be kept secret (they can be included in a transmitted message). Must
+        be the same number of bytes as the ``block_size`` of the cipher. Do not
+        reuse an ``initialization_vector`` with a given ``key``.
 
 .. class:: GCM(initialization_vector, tag=None)
 
@@ -282,13 +268,10 @@
     **This mode does not require padding.**
 
     :param bytes initialization_vector: Must be random bytes. They do not need
-                                        to be kept secret (they can be included
-                                        in a transmitted message). NIST
-                                        `recommends 96-bit IV length`_ for
-                                        performance critical situations, but it
-                                        can be up to 2\ :sup:`64` - 1 bits.
-                                        Do not reuse an ``initialization_vector``
-                                        with a given ``key``.
+        to be kept secret (they can be included in a transmitted message). NIST
+        `recommends 96-bit IV length`_ for performance critical situations, but
+        it can be up to 2\ :sup:`64` - 1 bits. Do not reuse an
+        ``initialization_vector`` with a given ``key``.
 
     .. note::
 
@@ -300,8 +283,8 @@
         (32-bits). Applications **must** verify the tag is the expected length
         to guarantee the expected security margin.
 
-    :param bytes tag: The tag bytes to verify during decryption. When encrypting
-                      this must be None.
+    :param bytes tag: The tag bytes to verify during decryption. When
+        encrypting this must be ``None``.
 
     .. testcode::
 
@@ -428,8 +411,7 @@
 
         :return bytes: Returns the remainder of the data.
         :raises ValueError: This is raised when the data provided isn't
-                            correctly padded to be a multiple of the
-                            algorithm's block size.
+            correctly padded to be a multiple of the algorithm's block size.
 
         Once ``finalize`` is called this object can no longer be used and
         :meth:`update` and :meth:`finalize` will raise
@@ -473,7 +455,7 @@
 
         :return bytes: Returns the tag value as bytes.
         :raises: :class:`~cryptography.exceptions.NotYetFinalized` if called
-                 before the context is finalized.
+            before the context is finalized.
 
 
 .. _`described by Colin Percival`: http://www.daemonology.net/blog/2009-06-11-cryptographic-right-answers.html
diff --git a/docs/hazmat/primitives/twofactor.rst b/docs/hazmat/primitives/twofactor.rst
index 9d66161..3df1a14 100644
--- a/docs/hazmat/primitives/twofactor.rst
+++ b/docs/hazmat/primitives/twofactor.rst
@@ -13,14 +13,14 @@
 
 .. currentmodule:: cryptography.hazmat.primitives.twofactor.hotp
 
-.. class:: HOTP(key, length, backend)
+.. class:: HOTP(key, length, algorithm, backend)
 
     .. versionadded:: 0.3
 
-    HOTP objects take a ``key`` and ``length`` parameter. The ``key``
-    should be randomly generated bytes and is recommended to be 160 bits in
-    length. The ``length`` parameter controls the length of the generated
-    one time password and must be >= 6 and <= 8.
+    HOTP objects take a ``key``, ``length`` and ``algorithm`` parameter. The
+    ``key`` should be randomly generated bytes and is recommended to be 160
+    bits in length. The ``length`` parameter controls the length of the
+    generated one time password and must be >= 6 and <= 8.
 
     This is an implementation of :rfc:`4226`.
 
@@ -29,55 +29,64 @@
         >>> import os
         >>> from cryptography.hazmat.backends import default_backend
         >>> from cryptography.hazmat.primitives.twofactor.hotp import HOTP
+        >>> from cryptography.hazmat.primitives.hashes import SHA1
+        >>> key = os.urandom(16)
+        >>> hotp = HOTP(key, 6, SHA1(), backend=default_backend())
+        >>> hotp_value = hotp.generate(0)
+        >>> hotp.verify(hotp_value, 0)
 
-        >>> key = b"12345678901234567890"
-        >>> hotp = HOTP(key, 6, backend=default_backend())
-        >>> hotp.generate(0)
-        '755224'
-        >>> hotp.verify(b"755224", 0)
-
-    :param bytes key: Secret key as ``bytes``. This value must be generated in a
-                      cryptographically secure fashion and be at least 128 bits.
-                      It is recommended that the key be 160 bits.
+    :param bytes key: Per-user secret key. This value must be kept secret
+                      and be at least 128 bits. It is recommended that the
+                      key be 160 bits.
     :param int length: Length of generated one time password as ``int``.
+    :param HashAlgorithm algorithm: A
+        :class:`~cryptography.hazmat.primitives.hashes`
+        provider.
     :param backend: A
         :class:`~cryptography.hazmat.backends.interfaces.HMACBackend`
         provider.
-    :raises ValueError: This is raised if the provided ``key`` is shorter 128 bits
-                        or if the ``length`` parameter is not between 6 to 8.
-
+    :raises ValueError: This is raised if the provided ``key`` is shorter than
+        128 bits or if the ``length`` parameter is not 6, 7 or 8.
+    :raises UnsupportedAlgorithm: This is raised if the provided ``algorithm``
+        is not :class:`~cryptography.hazmat.primitives.hashes.SHA1()`,
+        :class:`~cryptography.hazmat.primitives.hashes.SHA256()` or
+        :class:`~cryptography.hazmat.primitives.hashes.SHA512()`.
 
     .. method:: generate(counter)
 
-        :param int counter: The counter value used to generate the one time password.
+        :param int counter: The counter value used to generate the one time
+            password.
         :return bytes: A one time password value.
 
     .. method:: verify(hotp, counter)
 
         :param bytes hotp: The one time password value to validate.
-        :param bytes counter: The counter value to validate against.
-        :raises cryptography.exceptions.InvalidToken: This is raised when the supplied HOTP
-                                                      does not match the expected HOTP.
+        :param int counter: The counter value to validate against.
+        :raises cryptography.exceptions.InvalidToken: This is raised when the
+            supplied HOTP does not match the expected HOTP.
 
 Throttling
-----------
+~~~~~~~~~~
 
-Due to the fact that the HOTP algorithm generates rather short tokens that are 6 - 8 digits
-long, brute force attacks are possible. It is highly recommended that the server that
-validates the token implement a throttling scheme that locks out the account for a period of
-time after a number of failed attempts. The number of allowed attempts should be as low as
-possible while still ensuring that usability is not significantly impacted.
+Due to the fact that the HOTP algorithm generates rather short tokens that are
+6 - 8 digits long, brute force attacks are possible. It is highly recommended
+that the server that validates the token implement a throttling scheme that
+locks out the account for a period of time after a number of failed attempts.
+The number of allowed attempts should be as low as possible while still
+ensuring that usability is not significantly impacted.
 
 Re-synchronization of the Counter
----------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The server's counter value should only be incremented on a successful HOTP authentication.
-However, the counter on the client is incremented every time a new HOTP value is requested.
-This can lead to the counter value being out of synchronization between the client and server.
+The server's counter value should only be incremented on a successful HOTP
+authentication. However, the counter on the client is incremented every time a
+new HOTP value is requested. This can lead to the counter value being out of
+synchronization between the client and server.
 
-Due to this, it is highly recommended that the server sets a look-ahead window that allows the
-server to calculate the next ``x`` HOTP values and check them against the supplied HOTP value.
-This can be accomplished with something similar to the following code.
+Due to this, it is highly recommended that the server sets a look-ahead window
+that allows the server to calculate the next ``x`` HOTP values and check them
+against the supplied HOTP value. This can be accomplished with something
+similar to the following code.
 
 .. code-block:: python
 
@@ -86,11 +95,66 @@
         correct_counter = None
 
         otp = HOTP(key, 6, default_backend())
-        for count in range(counter, counter+look_ahead):
+        for count in range(counter, counter + look_ahead):
             try:
                 otp.verify(hotp, count)
                 correct_counter = count
             except InvalidToken:
                 pass
 
-        return correct_counter
\ No newline at end of file
+        return correct_counter
+
+.. currentmodule:: cryptography.hazmat.primitives.twofactor.totp
+
+.. class:: TOTP(key, length, algorithm, time_step, backend)
+
+    TOTP objects take a ``key``, ``length``, ``algorithm`` and ``time_step``
+    parameter. The ``key`` should be randomly generated bytes and is recommended
+    to be as long as your hash function's output (e.g 256-bit for SHA256).
+    The ``length`` parameter controls the length of the generated one time
+    password and must be >= 6 and <= 8.
+
+    This is an implementation of :rfc:`6238`.
+
+    .. doctest::
+
+        >>> import os
+        >>> import time
+        >>> from cryptography.hazmat.backends import default_backend
+        >>> from cryptography.hazmat.primitives.twofactor.totp import TOTP
+        >>> from cryptography.hazmat.primitives.hashes import SHA1
+        >>> key = os.urandom(16)
+        >>> totp = TOTP(key, 8, SHA1(), 30, backend=default_backend())
+        >>> time_value = time.time()
+        >>> totp_value = totp.generate(time_value)
+        >>> totp.verify(totp_value, time_value)
+
+    :param bytes key: Per-user secret key. This value must be kept secret
+                      and be at least 128 bits. It is recommended that the
+                      key be 160 bits.
+    :param int length: Length of generated one time password as ``int``.
+    :param HashAlgorithm algorithm: A
+        :class:`~cryptography.hazmat.primitives.hashes`
+        provider.
+    :param int time_step: The time step size. The recommended size is 30.
+    :param backend: A
+        :class:`~cryptography.hazmat.backends.interfaces.HMACBackend`
+        provider.
+    :raises ValueError: This is raised if the provided ``key`` is shorter than
+        128 bits or if the ``length`` parameter is not 6, 7 or 8.
+    :raises UnsupportedAlgorithm: This is raised if the provided ``algorithm``
+        is not :class:`~cryptography.hazmat.primitives.hashes.SHA1()`,
+        :class:`~cryptography.hazmat.primitives.hashes.SHA256()` or
+        :class:`~cryptography.hazmat.primitives.hashes.SHA512()`.
+
+    .. method:: generate(time)
+
+        :param int time: The time value used to generate the one time password.
+        :return bytes: A one time password value.
+
+    .. method:: verify(totp, time)
+
+        :param bytes totp: The one time password value to validate.
+        :param int time: The time value to validate against.
+        :raises cryptography.exceptions.InvalidToken: This is raised when the
+            supplied TOTP does not match the expected TOTP.
diff --git a/docs/random-numbers.rst b/docs/random-numbers.rst
index cd73a7b..12969d1 100644
--- a/docs/random-numbers.rst
+++ b/docs/random-numbers.rst
@@ -8,8 +8,8 @@
 provide a cryptographically secure random number generator, which can result in
 major security issues depending on the algorithms in use.
 
-Therefore, it is our recommendation to always use your operating system's
-provided random number generator, which is available as ``os.urandom()``. For
+Therefore, it is our recommendation to `always use your operating system's
+provided random number generator`_, which is available as ``os.urandom()``. For
 example, if you need 16 bytes of random data for an initialization vector, you
 can obtain them with:
 
@@ -18,3 +18,5 @@
     >>> import os
     >>> os.urandom(16)
     '...'
+
+.. _`always use your operating system's provided random number generator`: http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/
diff --git a/setup.py b/setup.py
index 81a50f4..681b903 100644
--- a/setup.py
+++ b/setup.py
@@ -11,10 +11,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import os
+import sys
 from distutils.command.build import build
 
 from setuptools import setup, find_packages
-
+from setuptools.command.test import test as TestCommand
 
 base_dir = os.path.dirname(__file__)
 
@@ -31,8 +32,14 @@
     SIX_DEPENDENCY
 ]
 
+test_requirements = [
+    "pytest",
+    "pretend",
+    "iso8601"
+]
 
-class cffi_build(build):
+
+class CFFIBuild(build):
     """
     This class exists, instead of just providing ``ext_modules=[...]`` directly
     in ``setup()`` because importing cryptography requires we have several
@@ -64,6 +71,19 @@
         build.finalize_options(self)
 
 
+class PyTest(TestCommand):
+    def finalize_options(self):
+        TestCommand.finalize_options(self)
+        self.test_args = []
+        self.test_suite = True
+
+    def run_tests(self):
+        # Import here because in module scope the eggs are not loaded.
+        import pytest
+        errno = pytest.main(self.test_args)
+        sys.exit(errno)
+
+
 with open(os.path.join(base_dir, "README.rst")) as f:
     long_description = f.read()
 
@@ -105,11 +125,13 @@
 
     install_requires=requirements,
     setup_requires=requirements,
+    tests_require=test_requirements,
 
     # for cffi
     zip_safe=False,
     ext_package="cryptography",
     cmdclass={
-        "build": cffi_build,
+        "build": CFFIBuild,
+        "test": PyTest,
     }
 )
diff --git a/tests/hazmat/primitives/twofactor/test_hotp.py b/tests/hazmat/primitives/twofactor/test_hotp.py
index ec619b5..7c58427 100644
--- a/tests/hazmat/primitives/twofactor/test_hotp.py
+++ b/tests/hazmat/primitives/twofactor/test_hotp.py
@@ -15,10 +15,11 @@
 
 import pytest
 
-from cryptography.exceptions import InvalidToken
+from cryptography.exceptions import InvalidToken, UnsupportedAlgorithm
 from cryptography.hazmat.primitives.twofactor.hotp import HOTP
 from cryptography.hazmat.primitives import hashes
 from tests.utils import load_vectors_from_file, load_nist_vectors
+from cryptography.hazmat.primitives.hashes import MD5, SHA1
 
 vectors = load_vectors_from_file(
     "twofactor/rfc-4226.txt", load_nist_vectors)
@@ -30,18 +31,23 @@
 )
 @pytest.mark.hmac
 class TestHOTP(object):
-
     def test_invalid_key_length(self, backend):
         secret = os.urandom(10)
 
         with pytest.raises(ValueError):
-            HOTP(secret, 6, backend)
+            HOTP(secret, 6, SHA1(), backend)
 
     def test_invalid_hotp_length(self, backend):
         secret = os.urandom(16)
 
         with pytest.raises(ValueError):
-            HOTP(secret, 4, backend)
+            HOTP(secret, 4, SHA1(), backend)
+
+    def test_invalid_algorithm(self, backend):
+        secret = os.urandom(16)
+
+        with pytest.raises(UnsupportedAlgorithm):
+            HOTP(secret, 6, MD5(), backend)
 
     @pytest.mark.parametrize("params", vectors)
     def test_truncate(self, backend, params):
@@ -49,7 +55,7 @@
         counter = int(params["counter"])
         truncated = params["truncated"]
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         assert hotp._dynamic_truncate(counter) == int(truncated.decode(), 16)
 
@@ -59,7 +65,7 @@
         counter = int(params["counter"])
         hotp_value = params["hotp"]
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         assert hotp.generate(counter) == hotp_value
 
@@ -69,7 +75,7 @@
         counter = int(params["counter"])
         hotp_value = params["hotp"]
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         assert hotp.verify(hotp_value, counter) is None
 
@@ -77,7 +83,7 @@
         secret = b"12345678901234567890"
         counter = 0
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         with pytest.raises(InvalidToken):
             hotp.verify(b"123456", counter)
diff --git a/tests/hazmat/primitives/twofactor/test_totp.py b/tests/hazmat/primitives/twofactor/test_totp.py
new file mode 100644
index 0000000..a4a108b
--- /dev/null
+++ b/tests/hazmat/primitives/twofactor/test_totp.py
@@ -0,0 +1,129 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from cryptography.exceptions import InvalidToken
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.twofactor.totp import TOTP
+from tests.utils import load_vectors_from_file, load_nist_vectors
+
+vectors = load_vectors_from_file(
+    "twofactor/rfc-6238.txt", load_nist_vectors)
+
+
+@pytest.mark.hmac
+class TestTOTP(object):
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA1()),
+        skip_message="Does not support HMAC-SHA1."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA1"])
+    def test_generate_sha1(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA256()),
+        skip_message="Does not support HMAC-SHA256."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA256"])
+    def test_generate_sha256(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA256(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA512()),
+        skip_message="Does not support HMAC-SHA512."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA512"])
+    def test_generate_sha512(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA512(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA1()),
+        skip_message="Does not support HMAC-SHA1."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA1"])
+    def test_verify_sha1(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+
+        assert totp.verify(totp_value, time) is None
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA256()),
+        skip_message="Does not support HMAC-SHA256."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA256"])
+    def test_verify_sha256(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA256(), 30, backend)
+
+        assert totp.verify(totp_value, time) is None
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA512()),
+        skip_message="Does not support HMAC-SHA512."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA512"])
+    def test_verify_sha512(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA512(), 30, backend)
+
+        assert totp.verify(totp_value, time) is None
+
+    def test_invalid_verify(self, backend):
+        secret = b"12345678901234567890"
+        time = 59
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+
+        with pytest.raises(InvalidToken):
+            totp.verify(b"12345678", time)
+
+    def test_floating_point_time_generate(self, backend):
+        secret = b"12345678901234567890"
+        time = 59.1
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+
+        assert totp.generate(time) == b"94287082"
diff --git a/tox.ini b/tox.ini
index 5ff0877..4248db3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -41,3 +41,4 @@
 
 [flake8]
 exclude = .tox,*.egg
+select = E,W,F