diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 1ab19cd1a6..59f687e0f1 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -324,7 +324,7 @@ class AuthHandler(BaseHandler):
 
     def _check_password(self, user_id, password, stored_hash):
         """Checks that user_id has passed password, raises LoginError if not."""
-        if not bcrypt.checkpw(password, stored_hash):
+        if not self.validate_hash(password, stored_hash):
             logger.warn("Failed password login for user %s", user_id)
             raise LoginError(403, "", errcode=Codes.FORBIDDEN)
 
@@ -369,7 +369,7 @@ class AuthHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def set_password(self, user_id, newpassword):
-        password_hash = bcrypt.hashpw(newpassword, bcrypt.gensalt())
+        password_hash = self.hash(newpassword)
 
         yield self.store.user_set_password_hash(user_id, password_hash)
         yield self.store.user_delete_access_tokens(user_id)
@@ -391,3 +391,26 @@ class AuthHandler(BaseHandler):
     def _remove_session(self, session):
         logger.debug("Removing session %s", session)
         del self.sessions[session["id"]]
+
+    def hash(self, password):
+        """Computes a secure hash of password.
+
+        Args:
+            password (str): Password to hash.
+
+        Returns:
+            Hashed password (str).
+        """
+        return bcrypt.hashpw(password, bcrypt.gensalt())
+
+    def validate_hash(self, password, stored_hash):
+        """Validates that self.hash(password) == stored_hash.
+
+        Args:
+            password (str): Password to hash.
+            stored_hash (str): Expected hash value.
+
+        Returns:
+            Whether self.hash(password) == stored_hash (bool).
+        """
+        return bcrypt.checkpw(password, stored_hash)
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 56d125f753..855bb58522 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -82,7 +82,7 @@ class RegistrationHandler(BaseHandler):
         yield run_on_reactor()
         password_hash = None
         if password:
-            password_hash = bcrypt.hashpw(password, bcrypt.gensalt())
+            password_hash = self.auth_handler().hash(password)
 
         if localpart:
             yield self.check_username(localpart)
diff --git a/tests/utils.py b/tests/utils.py
index 3766a994f2..dd19a16fc7 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -27,6 +27,7 @@ from twisted.enterprise.adbapi import ConnectionPool
 
 from collections import namedtuple
 from mock import patch, Mock
+import hashlib
 import urllib
 import urlparse
 
@@ -67,6 +68,18 @@ def setup_test_homeserver(name="test", datastore=None, config=None, **kargs):
             **kargs
         )
 
+    # bcrypt is far too slow to be doing in unit tests
+    def swap_out_hash_for_testing(old_build_handlers):
+        def build_handlers():
+            handlers = old_build_handlers()
+            auth_handler = handlers.auth_handler
+            auth_handler.hash = lambda p: hashlib.md5(p).hexdigest()
+            auth_handler.validate_hash = lambda p, h: hashlib.md5(p).hexdigest() == h
+            return handlers
+        return build_handlers
+
+    hs.build_handlers = swap_out_hash_for_testing(hs.build_handlers)
+
     defer.returnValue(hs)