diff --git a/letsencrypt/account.py b/letsencrypt/account.py
index 12389ebfd..b2b00a32e 100644
--- a/letsencrypt/account.py
+++ b/letsencrypt/account.py
@@ -1,9 +1,11 @@
 """Creates ACME accounts for server."""
 import datetime
+import hashlib
 import logging
 import os
 import socket
 
+from cryptography.hazmat.primitives import serialization
 import pyrfc3339
 import pytz
 import zope.component
@@ -20,15 +22,13 @@ from letsencrypt import le_util
 logger = logging.getLogger(__name__)
 
 
-class Account(object):
+class Account(object):  # pylint: disable=too-few-public-methods
     """ACME protocol registration.
 
     :ivar .RegistrationResource regr: Registration Resource
     :ivar .JWK key: Authorized Account Key
     :ivar .Meta: Account metadata
-
-    .. note:: ``creation_dt`` and ``creation_host`` are useful in
-        cross-machine migration scenarios.
+    :ivar str id: Globally unique account identifier.
 
     """
 
@@ -38,6 +38,9 @@ class Account(object):
         :ivar datetime.datetime creation_dt: Creation date and time (UTC).
         :ivar str creation_host: FQDN of host, where account has been created.
 
+        .. note:: ``creation_dt`` and ``creation_host`` are useful in
+            cross-machine migration scenarios.
+
         """
         creation_dt = acme_fields.RFC3339Field("creation_dt")
         creation_host = jose.Field("creation_host")
@@ -51,18 +54,16 @@ class Account(object):
                 tz=pytz.UTC).replace(microsecond=0),
             creation_host=socket.getfqdn()) if meta is None else meta
 
-    @property
-    def id(self):  # pylint: disable=invalid-name
-        """Globally unique account identifier.
-
-        Implementation note: Email? Multiple accounts can have the same
-        email address. Registration URI? Assigned by the server, not
-        guaranteed to be stable over time, nor cannonical URI can be
-        generated. One could use the account key (fingerprint), as ACME
-        protocol doesn't allow it to be updated...
-
-        """
-        return self.slug
+        self.id = hashlib.md5(  # pylint: disable=invalid-name
+            self.key.key.public_key().public_bytes(
+                encoding=serialization.Encoding.DER,
+                format=serialization.PublicFormat.SubjectPublicKeyInfo)
+        ).hexdigest()
+        # Implementation note: Email? Multiple accounts can have the
+        # same email address. Registration URI? Assigned by the
+        # server, not guaranteed to be stable over time, nor
+        # cannonical URI can be generated. ACME protocol doesn't allow
+        # account key (and thus its fingerprint) to be updated...
 
     @property
     def slug(self):
diff --git a/letsencrypt/tests/account_test.py b/letsencrypt/tests/account_test.py
index bd34edc56..c0a3f1848 100644
--- a/letsencrypt/tests/account_test.py
+++ b/letsencrypt/tests/account_test.py
@@ -45,7 +45,7 @@ class AccountTest(unittest.TestCase):
 
     def test_id(self):
         self.assertEqual(
-            self.acc.id, "test.letsencrypt.org@2015-07-04T14:04:10Z")
+            self.acc.id, "2ba35a3bdf380ed76a5ac9e740568395")
 
     def test_slug(self):
         self.assertEqual(
@@ -54,7 +54,7 @@ class AccountTest(unittest.TestCase):
     def test_repr(self):
         self.assertEqual(
             repr(self.acc),
-            "<Account(test.letsencrypt.org@2015-07-04T14:04:10Z)>")
+            "<Account(2ba35a3bdf380ed76a5ac9e740568395)>")
 
 
 class ReportNewAccountTest(unittest.TestCase):
diff --git a/letsencrypt/tests/display/ops_test.py b/letsencrypt/tests/display/ops_test.py
index aba711150..6f4b2f317 100644
--- a/letsencrypt/tests/display/ops_test.py
+++ b/letsencrypt/tests/display/ops_test.py
@@ -1,5 +1,6 @@
 """Test letsencrypt.display.ops."""
 import os
+import pkg_resources
 import sys
 import tempfile
 import unittest
@@ -7,6 +8,7 @@ import unittest
 import mock
 import zope.component
 
+from acme import jose
 from acme import messages
 
 from letsencrypt import account
@@ -15,6 +17,10 @@ from letsencrypt import interfaces
 from letsencrypt.display import util as display_util
 
 
+KEY = jose.JWKRSA.load(pkg_resources.resource_string(
+    "letsencrypt.tests", os.path.join("testdata", "rsa512_key.pem")))
+
+
 class ChoosePluginTest(unittest.TestCase):
     """Tests for letsencrypt.display.ops.choose_plugin."""
 
@@ -186,7 +192,7 @@ class ChooseAccountTest(unittest.TestCase):
             accounts_dir=self.accounts_dir,
             account_keys_dir=self.account_keys_dir,
             server="letsencrypt-demo.org")
-        self.key = mock.MagicMock()
+        self.key = KEY
 
         self.acc1 = account.Account(messages.RegistrationResource(
             uri=None, new_authzr_uri=None, body=messages.Registration.from_data(