diff --git a/hmac/hmac.py b/hmac/hmac.py
new file mode 100644
index 00000000..77785a2d
--- /dev/null
+++ b/hmac/hmac.py
@@ -0,0 +1,144 @@
+"""HMAC (Keyed-Hashing for Message Authentication) Python module.
+
+Implements the HMAC algorithm as described by RFC 2104.
+"""
+
+import warnings as _warnings
+from _operator import _compare_digest as compare_digest
+import hashlib as _hashlib
+
+trans_5C = bytes((x ^ 0x5C) for x in range(256))
+trans_36 = bytes((x ^ 0x36) for x in range(256))
+
+# The size of the digests returned by HMAC depends on the underlying
+# hashing module used.  Use digest_size from the instance of HMAC instead.
+digest_size = None
+
+
+
+class HMAC:
+    """RFC 2104 HMAC class.  Also complies with RFC 4231.
+
+    This supports the API for Cryptographic Hash Functions (PEP 247).
+    """
+    blocksize = 64  # 512-bit HMAC; can be changed in subclasses.
+
+    def __init__(self, key, msg = None, digestmod = None):
+        """Create a new HMAC object.
+
+        key:       key for the keyed hash object.
+        msg:       Initial input for the hash, if provided.
+        digestmod: A module supporting PEP 247.  *OR*
+                   A hashlib constructor returning a new hash object. *OR*
+                   A hash name suitable for hashlib.new().
+                   Defaults to hashlib.md5.
+                   Implicit default to hashlib.md5 is deprecated and will be
+                   removed in Python 3.6.
+
+        Note: key and msg must be a bytes or bytearray objects.
+        """
+
+        if not isinstance(key, (bytes, bytearray)):
+            raise TypeError("key: expected bytes or bytearray, but got %r" % type(key).__name__)
+
+        if digestmod is None:
+            _warnings.warn("HMAC() without an explicit digestmod argument "
+                           "is deprecated.", PendingDeprecationWarning, 2)
+            digestmod = _hashlib.md5
+
+        if callable(digestmod):
+            self.digest_cons = digestmod
+        elif isinstance(digestmod, str):
+            self.digest_cons = lambda d=b'': _hashlib.new(digestmod, d)
+        else:
+            self.digest_cons = lambda d=b'': digestmod.new(d)
+
+        self.outer = self.digest_cons()
+        self.inner = self.digest_cons()
+        self.digest_size = self.inner.digest_size
+
+        if hasattr(self.inner, 'block_size'):
+            blocksize = self.inner.block_size
+            if blocksize < 16:
+                _warnings.warn('block_size of %d seems too small; using our '
+                               'default of %d.' % (blocksize, self.blocksize),
+                               RuntimeWarning, 2)
+                blocksize = self.blocksize
+        else:
+            _warnings.warn('No block_size attribute on given digest object; '
+                           'Assuming %d.' % (self.blocksize),
+                           RuntimeWarning, 2)
+            blocksize = self.blocksize
+
+        # self.blocksize is the default blocksize. self.block_size is
+        # effective block size as well as the public API attribute.
+        self.block_size = blocksize
+
+        if len(key) > blocksize:
+            key = self.digest_cons(key).digest()
+
+        key = key + bytes(blocksize - len(key))
+        self.outer.update(key.translate(trans_5C))
+        self.inner.update(key.translate(trans_36))
+        if msg is not None:
+            self.update(msg)
+
+    @property
+    def name(self):
+        return "hmac-" + self.inner.name
+
+    def update(self, msg):
+        """Update this hashing object with the string msg.
+        """
+        self.inner.update(msg)
+
+    def copy(self):
+        """Return a separate copy of this hashing object.
+
+        An update to this copy won't affect the original object.
+        """
+        # Call __new__ directly to avoid the expensive __init__.
+        other = self.__class__.__new__(self.__class__)
+        other.digest_cons = self.digest_cons
+        other.digest_size = self.digest_size
+        other.inner = self.inner.copy()
+        other.outer = self.outer.copy()
+        return other
+
+    def _current(self):
+        """Return a hash object for the current state.
+
+        To be used only internally with digest() and hexdigest().
+        """
+        h = self.outer.copy()
+        h.update(self.inner.digest())
+        return h
+
+    def digest(self):
+        """Return the hash value of this hashing object.
+
+        This returns a string containing 8-bit data.  The object is
+        not altered in any way by this function; you can continue
+        updating the object after calling this function.
+        """
+        h = self._current()
+        return h.digest()
+
+    def hexdigest(self):
+        """Like digest(), but returns a string of hexadecimal digits instead.
+        """
+        h = self._current()
+        return h.hexdigest()
+
+def new(key, msg = None, digestmod = None):
+    """Create a new hashing object and return it.
+
+    key: The starting key for the hash.
+    msg: if available, will immediately be hashed into the object's starting
+    state.
+
+    You can now feed arbitrary strings into the object using its update()
+    method, and can ask for the hash value at any time by calling its digest()
+    method.
+    """
+    return HMAC(key, msg, digestmod)