diff --git a/stix2/__init__.py b/stix2/__init__.py
index f3e02b4..26eed6f 100644
--- a/stix2/__init__.py
+++ b/stix2/__init__.py
@@ -53,8 +53,8 @@ from .patterns import (
     RepeatQualifier, StartStopQualifier, StringConstant, TimestampConstant,
     WithinQualifier,
 )
-from .utils import new_version, revoke
 from .v20 import *  # This import will always be the latest STIX 2.X version
 from .version import __version__
+from .versioning import new_version, revoke
 
 _collect_stix2_mappings()
diff --git a/stix2/base.py b/stix2/base.py
index 645064a..bd5ce55 100644
--- a/stix2/base.py
+++ b/stix2/base.py
@@ -21,8 +21,8 @@ from .markings.utils import validate
 from .utils import (
     NOW, PREFIX_21_REGEX, find_property_index, format_datetime, get_timestamp,
 )
-from .utils import new_version as _new_version
-from .utils import revoke as _revoke
+from .versioning import new_version as _new_version
+from .versioning import revoke as _revoke
 
 try:
     from collections.abc import Mapping
@@ -351,24 +351,21 @@ class _Observable(_STIXBase):
     def __init__(self, **kwargs):
         # the constructor might be called independently of an observed data object
         self._STIXBase__valid_refs = kwargs.pop('_valid_refs', [])
-
-        self._allow_custom = kwargs.get('allow_custom', False)
         self._properties['extensions'].allow_custom = kwargs.get('allow_custom', False)
-
-        try:
-            # Since `spec_version` is optional, this is how we check for a 2.1 SCO
-            self._id_contributing_properties
-
-            if 'id' not in kwargs:
-                possible_id = self._generate_id(kwargs)
-                if possible_id is not None:
-                    kwargs['id'] = possible_id
-        except AttributeError:
-            # End up here if handling a 2.0 SCO, and don't need to do anything further
-            pass
-
         super(_Observable, self).__init__(**kwargs)
 
+        if 'id' not in kwargs and not isinstance(self, stix2.v20._Observable):
+            # Specific to 2.1+ observables: generate a deterministic ID
+            id_ = self._generate_id()
+
+            # Spec says fall back to UUIDv4 if no contributing properties were
+            # given.  That's what already happened (the following is actually
+            # overwriting the default uuidv4), so nothing to do here.
+            if id_ is not None:
+                # Can't assign to self (we're immutable), so slip the ID in
+                # more sneakily.
+                self._inner["id"] = id_
+
     def _check_ref(self, ref, prop, prop_name):
         """
         Only for checking `*_ref` or `*_refs` properties in spec_version 2.0
@@ -413,42 +410,53 @@ class _Observable(_STIXBase):
                 for ref in kwargs[prop_name]:
                     self._check_ref(ref, prop, prop_name)
 
-    def _generate_id(self, kwargs):
-        required_prefix = self._type + "--"
+    def _generate_id(self):
+        """
+        Generate a UUIDv5 for this observable, using its "ID contributing
+        properties".
 
-        properties_to_use = self._id_contributing_properties
-        if properties_to_use:
-            streamlined_object = {}
-            if "hashes" in kwargs and "hashes" in properties_to_use:
-                possible_hash = _choose_one_hash(kwargs["hashes"])
-                if possible_hash:
-                    streamlined_object["hashes"] = possible_hash
-            for key in properties_to_use:
-                if key != "hashes" and key in kwargs:
-                    if isinstance(kwargs[key], dict) or isinstance(kwargs[key], _STIXBase):
-                        temp_deep_copy = copy.deepcopy(dict(kwargs[key]))
-                        _recursive_stix_to_dict(temp_deep_copy)
-                        streamlined_object[key] = temp_deep_copy
-                    elif isinstance(kwargs[key], list):
-                        temp_deep_copy = copy.deepcopy(kwargs[key])
-                        _recursive_stix_list_to_dict(temp_deep_copy)
-                        streamlined_object[key] = temp_deep_copy
-                    else:
-                        streamlined_object[key] = kwargs[key]
-            if streamlined_object:
-                data = canonicalize(streamlined_object, utf8=False)
+        :return: The ID, or None if no ID contributing properties are set
+        """
+
+        id_ = None
+        json_serializable_object = {}
+
+        for key in self._id_contributing_properties:
+
+            if key in self:
+                obj_value = self[key]
+
+                if key == "hashes":
+                    serializable_value = _choose_one_hash(obj_value)
+
+                    if serializable_value is None:
+                        raise InvalidValueError(
+                            self, key, "No hashes given",
+                        )
 
-                # The situation is complicated w.r.t. python 2/3 behavior, so
-                # I'd rather not rely on particular exceptions being raised to
-                # determine what to do.  Better to just check the python version
-                # directly.
-                if six.PY3:
-                    return required_prefix + six.text_type(uuid.uuid5(SCO_DET_ID_NAMESPACE, data))
                 else:
-                    return required_prefix + six.text_type(uuid.uuid5(SCO_DET_ID_NAMESPACE, data.encode("utf-8")))
+                    serializable_value = _make_json_serializable(obj_value)
 
-        # We return None if there are no values specified for any of the id-contributing-properties
-        return None
+                json_serializable_object[key] = serializable_value
+
+        if json_serializable_object:
+
+            data = canonicalize(json_serializable_object, utf8=False)
+
+            # The situation is complicated w.r.t. python 2/3 behavior, so
+            # I'd rather not rely on particular exceptions being raised to
+            # determine what to do.  Better to just check the python version
+            # directly.
+            if six.PY3:
+                uuid_ = uuid.uuid5(SCO_DET_ID_NAMESPACE, data)
+            else:
+                uuid_ = uuid.uuid5(
+                    SCO_DET_ID_NAMESPACE, data.encode("utf-8"),
+                )
+
+            id_ = "{}--{}".format(self._type, six.text_type(uuid_))
+
+        return id_
 
 
 class _Extension(_STIXBase):
@@ -472,35 +480,102 @@ def _choose_one_hash(hash_dict):
         if k is not None:
             return {k: hash_dict[k]}
 
+    return None
+
 
 def _cls_init(cls, obj, kwargs):
     if getattr(cls, '__init__', object.__init__) is not object.__init__:
         cls.__init__(obj, **kwargs)
 
 
-def _recursive_stix_to_dict(input_dict):
-    for key in input_dict:
-        if isinstance(input_dict[key], dict):
-            _recursive_stix_to_dict(input_dict[key])
-        elif isinstance(input_dict[key], _STIXBase):
-            input_dict[key] = dict(input_dict[key])
+def _make_json_serializable(value):
+    """
+    Make the given value JSON-serializable; required for the JSON canonicalizer
+    to work.  This recurses into lists/dicts, converts stix objects to dicts,
+    etc.  "Convenience" types this library uses as property values are
+    JSON-serialized to produce a JSON-serializable value.  (So you will always
+    get strings for those.)
 
-            # There may stil be nested _STIXBase objects
-            _recursive_stix_to_dict(input_dict[key])
-        elif isinstance(input_dict[key], list):
-            _recursive_stix_list_to_dict(input_dict[key])
-        else:
-            pass
+    The conversion will not affect the passed in value.
+
+    :param value: The value to make JSON-serializable.
+    :return: The JSON-serializable value.
+    :raises ValueError: If value is None (since nulls are not allowed in STIX
+        objects).
+    """
+    if value is None:
+        raise ValueError("Illegal null value found in a STIX object")
+
+    json_value = value  # default assumption
+
+    if isinstance(value, Mapping):
+        json_value = {
+            k: _make_json_serializable(v)
+            for k, v in value.items()
+        }
+
+    elif isinstance(value, list):
+        json_value = [
+            _make_json_serializable(v)
+            for v in value
+        ]
+
+    elif not isinstance(value, (int, float, six.string_types, bool)):
+        # If a "simple" value which is not already JSON-serializable,
+        # JSON-serialize to a string and use that as our JSON-serializable
+        # value.  This applies to our datetime objects currently (timestamp
+        # properties), and could apply to any other "convenience" types this
+        # library uses for property values in the future.
+        json_value = json.dumps(value, ensure_ascii=False, cls=STIXJSONEncoder)
+
+        # If it looks like a string literal was output, strip off the quotes.
+        # Otherwise, a second pair will be added when it's canonicalized.  Also
+        # to be extra safe, we need to unescape.
+        if len(json_value) >= 2 and \
+                json_value[0] == '"' and json_value[-1] == '"':
+            json_value = _un_json_escape(json_value[1:-1])
+
+    return json_value
 
 
-def _recursive_stix_list_to_dict(input_list):
-    for i in range(len(input_list)):
-        if isinstance(input_list[i], _STIXBase):
-            input_list[i] = dict(input_list[i])
-        elif isinstance(input_list[i], dict):
-            pass
-        elif isinstance(input_list[i], list):
-            _recursive_stix_list_to_dict(input_list[i])
-        else:
-            continue
-        _recursive_stix_to_dict(input_list[i])
+_JSON_ESCAPE_RE = re.compile(r"\\.")
+# I don't think I should need to worry about the unicode escapes (\uXXXX)
+# since I use ensure_ascii=False when generating it.  I will just fix all
+# the other escapes, e.g. \n, \r, etc.
+#
+# This list is taken from RFC8259 section 7:
+# https://tools.ietf.org/html/rfc8259#section-7
+# Maps the second char of a "\X" style escape, to a replacement char
+_JSON_ESCAPE_MAP = {
+    '"': '"',
+    "\\": "\\",
+    "/": "/",
+    "b": "\b",
+    "f": "\f",
+    "n": "\n",
+    "r": "\r",
+    "t": "\t",
+}
+
+
+def _un_json_escape(json_string):
+    """
+    Removes JSON string literal escapes.  We should undo these things Python's
+    serializer does, so we can ensure they're done canonically.  The
+    canonicalizer should be in charge of everything, as much as is feasible.
+
+    :param json_string: String literal output of Python's JSON serializer,
+        minus the surrounding quotes.
+    :return: The unescaped string
+    """
+
+    def replace(m):
+        replacement = _JSON_ESCAPE_MAP.get(m.group(0)[1])
+        if replacement is None:
+            raise ValueError("Unrecognized JSON escape: " + m.group(0))
+
+        return replacement
+
+    result = _JSON_ESCAPE_RE.sub(replace, json_string)
+
+    return result
diff --git a/stix2/markings/granular_markings.py b/stix2/markings/granular_markings.py
index 5456f83..5021ec8 100644
--- a/stix2/markings/granular_markings.py
+++ b/stix2/markings/granular_markings.py
@@ -2,7 +2,8 @@
 
 from stix2 import exceptions
 from stix2.markings import utils
-from stix2.utils import is_marking, new_version
+from stix2.utils import is_marking
+from stix2.versioning import new_version
 
 
 def get_markings(obj, selectors, inherited=False, descendants=False, marking_ref=True, lang=True):
diff --git a/stix2/markings/object_markings.py b/stix2/markings/object_markings.py
index dc85dfa..5d4e4f1 100644
--- a/stix2/markings/object_markings.py
+++ b/stix2/markings/object_markings.py
@@ -2,7 +2,7 @@
 
 from stix2 import exceptions
 from stix2.markings import utils
-from stix2.utils import new_version
+from stix2.versioning import new_version
 
 
 def get_markings(obj):
diff --git a/stix2/pattern_visitor.py b/stix2/pattern_visitor.py
index 317ffa1..4ec2b20 100644
--- a/stix2/pattern_visitor.py
+++ b/stix2/pattern_visitor.py
@@ -40,6 +40,11 @@ def remove_terminal_nodes(parse_tree_nodes):
     return values
 
 
+_TIMESTAMP_RE = re.compile(r'\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d{1,6})?Z')
+
+
+def check_for_valid_timetamp_syntax(timestamp_string):
+    return _TIMESTAMP_RE.match(timestamp_string)
 
 
 
@@ -214,6 +219,14 @@ class STIXPatternVisitorForSTIX2():
     # Visit a parse tree produced by STIXPatternParser#startStopQualifier.
     def visitStartStopQualifier(self, ctx):
         children = self.visitChildren(ctx)
+        # 2.0 parser will accept any string, need to make sure it is a full STIX timestamp
+        if isinstance(children[1], StringConstant):
+            if not check_for_valid_timetamp_syntax(children[1].value):
+                raise (ValueError("Start time is not a legal timestamp"))
+        if isinstance(children[3], StringConstant):
+            if not check_for_valid_timetamp_syntax(children[3].value):
+                raise (ValueError("Stop time is not a legal timestamp"))
+
         return StartStopQualifier(children[1], children[3])
 
     # Visit a parse tree produced by STIXPatternParser#withinQualifier.
diff --git a/stix2/patterns.py b/stix2/patterns.py
index 6592335..5d7c0a2 100644
--- a/stix2/patterns.py
+++ b/stix2/patterns.py
@@ -669,12 +669,16 @@ class StartStopQualifier(_ExpressionQualifier):
             self.start_time = start_time
         elif isinstance(start_time, datetime.date):
             self.start_time = TimestampConstant(start_time)
+        elif isinstance(start_time, StringConstant):
+            self.start_time = StringConstant(start_time.value)
         else:
             raise ValueError("%s is not a valid argument for a Start/Stop Qualifier" % start_time)
         if isinstance(stop_time, TimestampConstant):
             self.stop_time = stop_time
         elif isinstance(stop_time, datetime.date):
             self.stop_time = TimestampConstant(stop_time)
+        elif isinstance(stop_time, StringConstant):
+            self.stop_time = StringConstant(stop_time.value)
         else:
             raise ValueError("%s is not a valid argument for a Start/Stop Qualifier" % stop_time)
 
diff --git a/stix2/properties.py b/stix2/properties.py
index bce5202..df962dd 100644
--- a/stix2/properties.py
+++ b/stix2/properties.py
@@ -17,10 +17,7 @@ from .exceptions import (
     MutuallyExclusivePropertiesError,
 )
 from .parsing import STIX2_OBJ_MAPS, parse, parse_observable
-from .utils import (
-    TYPE_21_REGEX, TYPE_REGEX, _get_dict, get_class_hierarchy_names,
-    parse_into_datetime,
-)
+from .utils import _get_dict, get_class_hierarchy_names, parse_into_datetime
 
 ID_REGEX_interoperability = re.compile(r"[0-9a-fA-F]{8}-"
                                        "[0-9a-fA-F]{4}-"
@@ -33,6 +30,8 @@ try:
 except ImportError:
     from collections import Mapping, defaultdict
 
+TYPE_REGEX = re.compile(r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-?$')
+TYPE_21_REGEX = re.compile(r'^([a-z][a-z0-9]*)+(-[a-z0-9]+)*\-?$')
 ERROR_INVALID_ID = (
     "not a valid STIX identifier, must match <object-type>--<UUID>: {}"
 )
@@ -547,7 +546,7 @@ def enumerate_types(types, spec_version):
     return return_types
 
 
-SELECTOR_REGEX = re.compile(r"^[a-z0-9_-]{3,250}(\.(\[\d+\]|[a-z0-9_-]{1,250}))*$")
+SELECTOR_REGEX = re.compile(r"^([a-z0-9_-]{3,250}(\.(\[\d+\]|[a-z0-9_-]{1,250}))*|id)$")
 
 
 class SelectorProperty(Property):
diff --git a/stix2/test/v20/test_granular_markings.py b/stix2/test/v20/test_granular_markings.py
index e912cc1..ae2da3b 100644
--- a/stix2/test/v20/test_granular_markings.py
+++ b/stix2/test/v20/test_granular_markings.py
@@ -1089,3 +1089,17 @@ def test_clear_marking_not_present(data):
     """Test clearing markings for a selector that has no associated markings."""
     with pytest.raises(MarkingNotFoundError):
         data = markings.clear_markings(data, ["labels"])
+
+
+def test_set_marking_on_id_property():
+    malware = Malware(
+        granular_markings=[
+            {
+                "selectors": ["id"],
+                "marking_ref": MARKING_IDS[0],
+            },
+        ],
+        **MALWARE_KWARGS
+    )
+
+    assert "id" in malware["granular_markings"][0]["selectors"]
diff --git a/stix2/test/v20/test_object_markings.py b/stix2/test/v20/test_object_markings.py
index 191f33a..6bd2269 100644
--- a/stix2/test/v20/test_object_markings.py
+++ b/stix2/test/v20/test_object_markings.py
@@ -14,6 +14,7 @@ from .constants import MARKING_IDS
 MALWARE_KWARGS = MALWARE_KWARGS_CONST.copy()
 MALWARE_KWARGS.update({
     'id': MALWARE_ID,
+    'type': 'malware',
     'created': FAKE_TIME,
     'modified': FAKE_TIME,
 })
diff --git a/stix2/test/v20/test_pattern_expressions.py b/stix2/test/v20/test_pattern_expressions.py
index d5cbb5b..a96d3b8 100644
--- a/stix2/test/v20/test_pattern_expressions.py
+++ b/stix2/test/v20/test_pattern_expressions.py
@@ -312,8 +312,8 @@ def test_set_op():
 
 
 def test_timestamp():
-    ts = stix2.TimestampConstant('2014-01-13T07:03:17Z')
-    assert str(ts) == "t'2014-01-13T07:03:17Z'"
+    ts = stix2.StringConstant('2014-01-13T07:03:17Z')
+    assert str(ts) == "'2014-01-13T07:03:17Z'"
 
 
 def test_boolean():
@@ -363,11 +363,6 @@ def test_invalid_integer_constant():
         stix2.IntegerConstant('foo')
 
 
-def test_invalid_timestamp_constant():
-    with pytest.raises(ValueError):
-        stix2.TimestampConstant('foo')
-
-
 def test_invalid_float_constant():
     with pytest.raises(ValueError):
         stix2.FloatConstant('foo')
@@ -461,23 +456,23 @@ def test_invalid_within_qualifier():
 
 def test_startstop_qualifier():
     qual = stix2.StartStopQualifier(
-        stix2.TimestampConstant('2016-06-01T00:00:00Z'),
-        datetime.datetime(2017, 3, 12, 8, 30, 0),
+        stix2.StringConstant('2016-06-01T00:00:00Z'),
+        stix2.StringConstant('2017-03-12T08:30:00Z'),
     )
-    assert str(qual) == "START t'2016-06-01T00:00:00Z' STOP t'2017-03-12T08:30:00Z'"
+    assert str(qual) == "START '2016-06-01T00:00:00Z' STOP '2017-03-12T08:30:00Z'"
 
     qual2 = stix2.StartStopQualifier(
-        datetime.date(2016, 6, 1),
-        stix2.TimestampConstant('2016-07-01T00:00:00Z'),
+        stix2.StringConstant("2016-06-01T00:00:00Z"),
+        stix2.StringConstant('2016-07-01T00:00:00Z'),
     )
-    assert str(qual2) == "START t'2016-06-01T00:00:00Z' STOP t'2016-07-01T00:00:00Z'"
+    assert str(qual2) == "START '2016-06-01T00:00:00Z' STOP '2016-07-01T00:00:00Z'"
 
 
 def test_invalid_startstop_qualifier():
     with pytest.raises(ValueError):
         stix2.StartStopQualifier(
             'foo',
-            stix2.TimestampConstant('2016-06-01T00:00:00Z'),
+            stix2.StringConstant('2016-06-01T00:00:00Z'),
         )
 
     with pytest.raises(ValueError):
@@ -508,6 +503,19 @@ def test_parsing_qualified_expression():
     ) == "[network-traffic:dst_ref.type = 'domain-name' AND network-traffic:dst_ref.value = 'example.com'] REPEATS 5 TIMES WITHIN 1800 SECONDS"
 
 
+def test_parsing_start_stop_qualified_expression():
+    patt_obj = create_pattern_object("[ipv4-addr:value = '1.2.3.4'] START '2016-06-01T00:00:00Z' STOP '2017-03-12T08:30:00Z'", version="2.0")
+
+    assert str(
+        patt_obj,
+    ) == "[ipv4-addr:value = '1.2.3.4'] START '2016-06-01T00:00:00Z' STOP '2017-03-12T08:30:00Z'"
+
+
+def test_parsing_illegal_start_stop_qualified_expression():
+    with pytest.raises(ValueError):
+        create_pattern_object("[ipv4-addr:value = '1.2.3.4'] START '2016-06-01' STOP '2017-03-12T08:30:00Z'", version="2.0")
+
+
 def test_list_constant():
     patt_obj = create_pattern_object("[network-traffic:src_ref.value IN ('10.0.0.0', '10.0.0.1', '10.0.0.2')]", version="2.0")
     assert str(patt_obj) == "[network-traffic:src_ref.value IN ('10.0.0.0', '10.0.0.1', '10.0.0.2')]"
diff --git a/stix2/test/v20/test_versioning.py b/stix2/test/v20/test_versioning.py
index 9974e42..03d43cc 100644
--- a/stix2/test/v20/test_versioning.py
+++ b/stix2/test/v20/test_versioning.py
@@ -1,6 +1,10 @@
 import pytest
 
 import stix2
+import stix2.exceptions
+import stix2.utils
+import stix2.v20
+import stix2.versioning
 
 from .constants import CAMPAIGN_MORE_KWARGS
 
@@ -142,7 +146,7 @@ def test_versioning_error_revoke_of_revoked():
 
 def test_making_new_version_dict():
     campaign_v1 = CAMPAIGN_MORE_KWARGS
-    campaign_v2 = stix2.utils.new_version(CAMPAIGN_MORE_KWARGS, name="fred")
+    campaign_v2 = stix2.versioning.new_version(CAMPAIGN_MORE_KWARGS, name="fred")
 
     assert campaign_v1['id'] == campaign_v2['id']
     assert campaign_v1['created_by_ref'] == campaign_v2['created_by_ref']
@@ -155,7 +159,7 @@ def test_making_new_version_dict():
 
 def test_versioning_error_dict_bad_modified_value():
     with pytest.raises(stix2.exceptions.InvalidValueError) as excinfo:
-        stix2.utils.new_version(CAMPAIGN_MORE_KWARGS, modified="2015-04-06T20:03:00.000Z")
+        stix2.versioning.new_version(CAMPAIGN_MORE_KWARGS, modified="2015-04-06T20:03:00.000Z")
 
     assert excinfo.value.cls == dict
     assert excinfo.value.prop_name == "modified"
@@ -171,7 +175,7 @@ def test_versioning_error_dict_no_modified_value():
         'created': "2016-04-06T20:03:00.000Z",
         'name': "Green Group Attacks Against Finance",
     }
-    campaign_v2 = stix2.utils.new_version(campaign_v1, modified="2017-04-06T20:03:00.000Z")
+    campaign_v2 = stix2.versioning.new_version(campaign_v1, modified="2017-04-06T20:03:00.000Z")
 
     assert str(campaign_v2['modified']) == "2017-04-06T20:03:00.000Z"
 
@@ -179,14 +183,14 @@ def test_versioning_error_dict_no_modified_value():
 def test_making_new_version_invalid_cls():
     campaign_v1 = "This is a campaign."
     with pytest.raises(ValueError) as excinfo:
-        stix2.utils.new_version(campaign_v1, name="fred")
+        stix2.versioning.new_version(campaign_v1, name="fred")
 
     assert 'cannot create new version of object of this type' in str(excinfo.value)
 
 
 def test_revoke_dict():
     campaign_v1 = CAMPAIGN_MORE_KWARGS
-    campaign_v2 = stix2.utils.revoke(campaign_v1)
+    campaign_v2 = stix2.versioning.revoke(campaign_v1)
 
     assert campaign_v1['id'] == campaign_v2['id']
     assert campaign_v1['created_by_ref'] == campaign_v2['created_by_ref']
@@ -198,12 +202,18 @@ def test_revoke_dict():
     assert campaign_v2['revoked']
 
 
+def test_revoke_unversionable():
+    sco = stix2.v20.File(name="data.txt")
+    with pytest.raises(ValueError):
+        sco.revoke()
+
+
 def test_versioning_error_revoke_of_revoked_dict():
     campaign_v1 = CAMPAIGN_MORE_KWARGS
-    campaign_v2 = stix2.utils.revoke(campaign_v1)
+    campaign_v2 = stix2.versioning.revoke(campaign_v1)
 
     with pytest.raises(stix2.exceptions.RevokeError) as excinfo:
-        stix2.utils.revoke(campaign_v2)
+        stix2.versioning.revoke(campaign_v2)
 
     assert excinfo.value.called_by == "revoke"
 
@@ -211,7 +221,7 @@ def test_versioning_error_revoke_of_revoked_dict():
 def test_revoke_invalid_cls():
     campaign_v1 = "This is a campaign."
     with pytest.raises(ValueError) as excinfo:
-        stix2.utils.revoke(campaign_v1)
+        stix2.versioning.revoke(campaign_v1)
 
     assert 'cannot revoke object of this type' in str(excinfo.value)
 
@@ -224,7 +234,7 @@ def test_remove_custom_stix_property():
         allow_custom=True,
     )
 
-    mal_nc = stix2.utils.remove_custom_stix(mal)
+    mal_nc = stix2.versioning.remove_custom_stix(mal)
 
     assert "x_custom" not in mal_nc
     assert (stix2.utils.parse_into_datetime(mal["modified"], precision="millisecond") <
@@ -243,15 +253,136 @@ def test_remove_custom_stix_object():
 
     animal = Animal(species="lion", animal_class="mammal")
 
-    nc = stix2.utils.remove_custom_stix(animal)
+    nc = stix2.versioning.remove_custom_stix(animal)
 
     assert nc is None
 
 
 def test_remove_custom_stix_no_custom():
     campaign_v1 = stix2.v20.Campaign(**CAMPAIGN_MORE_KWARGS)
-    campaign_v2 = stix2.utils.remove_custom_stix(campaign_v1)
+    campaign_v2 = stix2.versioning.remove_custom_stix(campaign_v1)
 
     assert len(campaign_v1.keys()) == len(campaign_v2.keys())
     assert campaign_v1.id == campaign_v2.id
     assert campaign_v1.description == campaign_v2.description
+
+
+def test_version_unversionable_dict():
+    f = {
+        "type": "file",
+        "name": "data.txt",
+    }
+
+    with pytest.raises(ValueError):
+        stix2.versioning.new_version(f)
+
+
+def test_version_sco_with_modified():
+    """
+    Ensure new_version() doesn't get tripped up over unversionable objects with
+    properties not used for versioning, but whose names conflict with
+    versioning properties.
+    """
+
+    file_sco = {
+        "type": "file",
+        "name": "data.txt",
+        "created": "1973-11-23T02:31:37Z",
+        "modified": "1991-05-13T19:24:57Z",
+    }
+
+    with pytest.raises(ValueError):
+        stix2.versioning.new_version(file_sco, name="newname.txt")
+
+    with pytest.raises(ValueError):
+        stix2.versioning.revoke(file_sco)
+
+    file_sco_obj = stix2.v20.File(
+        name="data.txt",
+        created="1973-11-23T02:31:37Z",
+        modified="1991-05-13T19:24:57Z",
+    )
+
+    with pytest.raises(ValueError):
+        stix2.versioning.new_version(file_sco_obj, name="newname.txt")
+
+    with pytest.raises(ValueError):
+        stix2.versioning.revoke(file_sco_obj)
+
+
+def test_version_sco_with_custom():
+    """
+    If we add custom properties named like versioning properties to an object
+    type which is otherwise unversionable, versioning should start working.
+    """
+
+    file_sco_obj = stix2.v20.File(
+        name="data.txt",
+        created="1973-11-23T02:31:37Z",
+        modified="1991-05-13T19:24:57Z",
+        revoked=False,  # the custom property
+        allow_custom=True,
+    )
+
+    new_file_sco_obj = stix2.versioning.new_version(
+        file_sco_obj, name="newname.txt",
+    )
+
+    assert new_file_sco_obj.name == "newname.txt"
+
+    revoked_obj = stix2.versioning.revoke(new_file_sco_obj)
+    assert revoked_obj.revoked
+
+
+def test_version_disable_custom():
+    m = stix2.v20.Malware(
+        name="foo", labels=["label"], description="Steals your identity!",
+        x_custom=123, allow_custom=True,
+    )
+
+    # Remove the custom property, and disallow custom properties in the
+    # resulting object.
+    m2 = stix2.versioning.new_version(m, x_custom=None, allow_custom=False)
+    assert "x_custom" not in m2
+
+    # Remove a regular property and leave the custom one, disallow custom
+    # properties, and make sure we get an error.
+    with pytest.raises(stix2.exceptions.ExtraPropertiesError):
+        stix2.versioning.new_version(m, description=None, allow_custom=False)
+
+
+def test_version_enable_custom():
+    m = stix2.v20.Malware(
+        name="foo", labels=["label"], description="Steals your identity!",
+    )
+
+    # Add a custom property to an object for which it was previously disallowed
+    m2 = stix2.versioning.new_version(m, x_custom=123, allow_custom=True)
+    assert "x_custom" in m2
+
+    # Add a custom property without enabling it, make sure we get an error
+    with pytest.raises(stix2.exceptions.ExtraPropertiesError):
+        stix2.versioning.new_version(m, x_custom=123, allow_custom=False)
+
+
+def test_version_propagate_custom():
+    m = stix2.v20.Malware(
+        name="foo", labels=["label"],
+    )
+
+    # Remember custom-not-allowed setting from original; produce error
+    with pytest.raises(stix2.exceptions.ExtraPropertiesError):
+        stix2.versioning.new_version(m, x_custom=123)
+
+    m2 = stix2.versioning.new_version(m, description="Steals your identity!")
+    assert "description" in m2
+    assert m2.description == "Steals your identity!"
+
+    m_custom = stix2.v20.Malware(
+        name="foo", labels=["label"], x_custom=123, allow_custom=True,
+    )
+
+    # Remember custom-allowed setting from original; should work
+    m2_custom = stix2.versioning.new_version(m_custom, x_other_custom="abc")
+    assert "x_other_custom" in m2_custom
+    assert m2_custom.x_other_custom == "abc"
diff --git a/stix2/test/v21/test_deterministic_ids.py b/stix2/test/v21/test_deterministic_ids.py
new file mode 100644
index 0000000..1e6e2d4
--- /dev/null
+++ b/stix2/test/v21/test_deterministic_ids.py
@@ -0,0 +1,339 @@
+from collections import OrderedDict
+import datetime
+import uuid
+
+import pytest
+import six
+
+import stix2.base
+import stix2.canonicalization.Canonicalize
+import stix2.exceptions
+from stix2.properties import (
+    BooleanProperty, DictionaryProperty, EmbeddedObjectProperty,
+    ExtensionsProperty, FloatProperty, HashesProperty, IDProperty,
+    IntegerProperty, ListProperty, StringProperty, TimestampProperty,
+    TypeProperty,
+)
+import stix2.v21
+
+SCO_DET_ID_NAMESPACE = uuid.UUID("00abedb4-aa42-466c-9c01-fed23315a9b7")
+
+
+def _uuid_from_id(id_):
+    dd_idx = id_.index("--")
+    uuid_str = id_[dd_idx+2:]
+    uuid_ = uuid.UUID(uuid_str)
+
+    return uuid_
+
+
+def _make_uuid5(name):
+    """
+    Make a STIX 2.1+ compliant UUIDv5 from a "name".
+    """
+    if six.PY3:
+        uuid_ = uuid.uuid5(SCO_DET_ID_NAMESPACE, name)
+    else:
+        uuid_ = uuid.uuid5(
+            SCO_DET_ID_NAMESPACE, name.encode("utf-8"),
+        )
+
+    return uuid_
+
+
+def test_no_contrib_props_defined():
+
+    class SomeSCO(stix2.v21._Observable):
+        _type = "some-sco"
+        _properties = OrderedDict((
+            ('type', TypeProperty(_type, spec_version='2.1')),
+            ('id', IDProperty(_type, spec_version='2.1')),
+            (
+                'extensions', ExtensionsProperty(
+                    spec_version='2.1', enclosing_type=_type,
+                ),
+            ),
+        ))
+        _id_contributing_properties = []
+
+    sco = SomeSCO()
+    uuid_ = _uuid_from_id(sco["id"])
+
+    assert uuid_.variant == uuid.RFC_4122
+    assert uuid_.version == 4
+
+
+def test_json_compatible_prop_values():
+    class SomeSCO(stix2.v21._Observable):
+        _type = "some-sco"
+        _properties = OrderedDict((
+            ('type', TypeProperty(_type, spec_version='2.1')),
+            ('id', IDProperty(_type, spec_version='2.1')),
+            (
+                'extensions', ExtensionsProperty(
+                    spec_version='2.1', enclosing_type=_type,
+                ),
+            ),
+            ('string', StringProperty()),
+            ('int', IntegerProperty()),
+            ('float', FloatProperty()),
+            ('bool', BooleanProperty()),
+            ('list', ListProperty(IntegerProperty())),
+            ('dict', DictionaryProperty(spec_version="2.1")),
+        ))
+        _id_contributing_properties = [
+            'string', 'int', 'float', 'bool', 'list', 'dict',
+        ]
+
+    obj = {
+        "string": "abc",
+        "int": 1,
+        "float": 1.5,
+        "bool": True,
+        "list": [1, 2, 3],
+        "dict": {"a": 1, "b": [2], "c": "three"},
+    }
+
+    sco = SomeSCO(**obj)
+
+    can_json = stix2.canonicalization.Canonicalize.canonicalize(obj, utf8=False)
+    expected_uuid5 = _make_uuid5(can_json)
+    actual_uuid5 = _uuid_from_id(sco["id"])
+
+    assert actual_uuid5 == expected_uuid5
+
+
+def test_json_incompatible_timestamp_value():
+    class SomeSCO(stix2.v21._Observable):
+        _type = "some-sco"
+        _properties = OrderedDict((
+            ('type', TypeProperty(_type, spec_version='2.1')),
+            ('id', IDProperty(_type, spec_version='2.1')),
+            (
+                'extensions', ExtensionsProperty(
+                    spec_version='2.1', enclosing_type=_type,
+                ),
+            ),
+            ('timestamp', TimestampProperty()),
+        ))
+        _id_contributing_properties = ['timestamp']
+
+    ts = datetime.datetime(1987, 1, 2, 3, 4, 5, 678900)
+
+    sco = SomeSCO(timestamp=ts)
+
+    obj = {
+        "timestamp": "1987-01-02T03:04:05.6789Z",
+    }
+
+    can_json = stix2.canonicalization.Canonicalize.canonicalize(obj, utf8=False)
+    expected_uuid5 = _make_uuid5(can_json)
+    actual_uuid5 = _uuid_from_id(sco["id"])
+
+    assert actual_uuid5 == expected_uuid5
+
+
+def test_embedded_object():
+    class SubObj(stix2.base._STIXBase):
+        _type = "sub-object"
+        _properties = OrderedDict((
+            ('value', StringProperty()),
+        ))
+
+    class SomeSCO(stix2.v21._Observable):
+        _type = "some-sco"
+        _properties = OrderedDict((
+            ('type', TypeProperty(_type, spec_version='2.1')),
+            ('id', IDProperty(_type, spec_version='2.1')),
+            (
+                'extensions', ExtensionsProperty(
+                    spec_version='2.1', enclosing_type=_type,
+                ),
+            ),
+            ('sub_obj', EmbeddedObjectProperty(type=SubObj)),
+        ))
+        _id_contributing_properties = ['sub_obj']
+
+    sub_obj = SubObj(value="foo")
+    sco = SomeSCO(sub_obj=sub_obj)
+
+    obj = {
+        "sub_obj": {
+            "value": "foo",
+        },
+    }
+
+    can_json = stix2.canonicalization.Canonicalize.canonicalize(obj, utf8=False)
+    expected_uuid5 = _make_uuid5(can_json)
+    actual_uuid5 = _uuid_from_id(sco["id"])
+
+    assert actual_uuid5 == expected_uuid5
+
+
+def test_empty_hash():
+    class SomeSCO(stix2.v21._Observable):
+        _type = "some-sco"
+        _properties = OrderedDict((
+            ('type', TypeProperty(_type, spec_version='2.1')),
+            ('id', IDProperty(_type, spec_version='2.1')),
+            (
+                'extensions', ExtensionsProperty(
+                    spec_version='2.1', enclosing_type=_type,
+                ),
+            ),
+            ('hashes', HashesProperty()),
+        ))
+        _id_contributing_properties = ['hashes']
+
+    with pytest.raises(stix2.exceptions.InvalidValueError):
+        SomeSCO(hashes={})
+
+
+@pytest.mark.parametrize(
+    "json_escaped, expected_unescaped", [
+        ("", ""),
+        ("a", "a"),
+        (r"\n", "\n"),
+        (r"\n\r\b\t\\\/\"", "\n\r\b\t\\/\""),
+        (r"\\n", r"\n"),
+        (r"\\\n", "\\\n"),
+    ],
+)
+def test_json_unescaping(json_escaped, expected_unescaped):
+    actual_unescaped = stix2.base._un_json_escape(json_escaped)
+    assert actual_unescaped == expected_unescaped
+
+
+def test_json_unescaping_bad_escape():
+    with pytest.raises(ValueError):
+        stix2.base._un_json_escape(r"\x")
+
+
+def test_deterministic_id_same_extra_prop_vals():
+    email_addr_1 = stix2.v21.EmailAddress(
+        value="john@example.com",
+        display_name="Johnny Doe",
+    )
+
+    email_addr_2 = stix2.v21.EmailAddress(
+        value="john@example.com",
+        display_name="Johnny Doe",
+    )
+
+    assert email_addr_1.id == email_addr_2.id
+
+    uuid_obj_1 = uuid.UUID(email_addr_1.id[-36:])
+    assert uuid_obj_1.variant == uuid.RFC_4122
+    assert uuid_obj_1.version == 5
+
+    uuid_obj_2 = uuid.UUID(email_addr_2.id[-36:])
+    assert uuid_obj_2.variant == uuid.RFC_4122
+    assert uuid_obj_2.version == 5
+
+
+def test_deterministic_id_diff_extra_prop_vals():
+    email_addr_1 = stix2.v21.EmailAddress(
+        value="john@example.com",
+        display_name="Johnny Doe",
+    )
+
+    email_addr_2 = stix2.v21.EmailAddress(
+        value="john@example.com",
+        display_name="Janey Doe",
+    )
+
+    assert email_addr_1.id == email_addr_2.id
+
+    uuid_obj_1 = uuid.UUID(email_addr_1.id[-36:])
+    assert uuid_obj_1.variant == uuid.RFC_4122
+    assert uuid_obj_1.version == 5
+
+    uuid_obj_2 = uuid.UUID(email_addr_2.id[-36:])
+    assert uuid_obj_2.variant == uuid.RFC_4122
+    assert uuid_obj_2.version == 5
+
+
+def test_deterministic_id_diff_contributing_prop_vals():
+    email_addr_1 = stix2.v21.EmailAddress(
+        value="john@example.com",
+        display_name="Johnny Doe",
+    )
+
+    email_addr_2 = stix2.v21.EmailAddress(
+        value="jane@example.com",
+        display_name="Janey Doe",
+    )
+
+    assert email_addr_1.id != email_addr_2.id
+
+    uuid_obj_1 = uuid.UUID(email_addr_1.id[-36:])
+    assert uuid_obj_1.variant == uuid.RFC_4122
+    assert uuid_obj_1.version == 5
+
+    uuid_obj_2 = uuid.UUID(email_addr_2.id[-36:])
+    assert uuid_obj_2.variant == uuid.RFC_4122
+    assert uuid_obj_2.version == 5
+
+
+def test_deterministic_id_no_contributing_props():
+    email_msg_1 = stix2.v21.EmailMessage(
+        is_multipart=False,
+    )
+
+    email_msg_2 = stix2.v21.EmailMessage(
+        is_multipart=False,
+    )
+
+    assert email_msg_1.id != email_msg_2.id
+
+    uuid_obj_1 = uuid.UUID(email_msg_1.id[-36:])
+    assert uuid_obj_1.variant == uuid.RFC_4122
+    assert uuid_obj_1.version == 4
+
+    uuid_obj_2 = uuid.UUID(email_msg_2.id[-36:])
+    assert uuid_obj_2.variant == uuid.RFC_4122
+    assert uuid_obj_2.version == 4
+
+
+def test_id_gen_recursive_dict_conversion_1():
+    file_observable = stix2.v21.File(
+        name="example.exe",
+        size=68 * 1000,
+        magic_number_hex="50000000",
+        hashes={
+            "SHA-256": "841a8921140aba50671ebb0770fecc4ee308c4952cfeff8de154ab14eeef4649",
+        },
+        extensions={
+            "windows-pebinary-ext": stix2.v21.WindowsPEBinaryExt(
+                pe_type="exe",
+                machine_hex="014c",
+                sections=[
+                    stix2.v21.WindowsPESection(
+                        name=".data",
+                        size=4096,
+                        entropy=7.980693,
+                        hashes={"SHA-256": "6e3b6f3978e5cd96ba7abee35c24e867b7e64072e2ecb22d0ee7a6e6af6894d0"},
+                    ),
+                ],
+            ),
+        },
+    )
+
+    assert file_observable.id == "file--ced31cd4-bdcb-537d-aefa-92d291bfc11d"
+
+
+def test_id_gen_recursive_dict_conversion_2():
+    wrko = stix2.v21.WindowsRegistryKey(
+        values=[
+            stix2.v21.WindowsRegistryValueType(
+                name="Foo",
+                data="qwerty",
+            ),
+            stix2.v21.WindowsRegistryValueType(
+                name="Bar",
+                data="42",
+            ),
+        ],
+    )
+
+    assert wrko.id == "windows-registry-key--36594eba-bcc7-5014-9835-0e154264e588"
diff --git a/stix2/test/v21/test_granular_markings.py b/stix2/test/v21/test_granular_markings.py
index 1c3194b..ff8fe26 100644
--- a/stix2/test/v21/test_granular_markings.py
+++ b/stix2/test/v21/test_granular_markings.py
@@ -1307,3 +1307,17 @@ def test_clear_marking_not_present(data):
     """Test clearing markings for a selector that has no associated markings."""
     with pytest.raises(MarkingNotFoundError):
         markings.clear_markings(data, ["malware_types"])
+
+
+def test_set_marking_on_id_property():
+    malware = Malware(
+        granular_markings=[
+            {
+                "selectors": ["id"],
+                "marking_ref": MARKING_IDS[0],
+            },
+        ],
+        **MALWARE_KWARGS
+    )
+
+    assert "id" in malware["granular_markings"][0]["selectors"]
diff --git a/stix2/test/v21/test_object_markings.py b/stix2/test/v21/test_object_markings.py
index a21fbf6..bb1c4ab 100644
--- a/stix2/test/v21/test_object_markings.py
+++ b/stix2/test/v21/test_object_markings.py
@@ -13,6 +13,7 @@ from .constants import MARKING_IDS
 MALWARE_KWARGS = MALWARE_KWARGS_CONST.copy()
 MALWARE_KWARGS.update({
     'id': MALWARE_ID,
+    'type': 'malware',
     'created': FAKE_TIME,
     'modified': FAKE_TIME,
 })
diff --git a/stix2/test/v21/test_observed_data.py b/stix2/test/v21/test_observed_data.py
index c13148a..e0fa456 100644
--- a/stix2/test/v21/test_observed_data.py
+++ b/stix2/test/v21/test_observed_data.py
@@ -1,6 +1,5 @@
 import datetime as dt
 import re
-import uuid
 
 import pytest
 import pytz
@@ -900,6 +899,27 @@ def test_file_example_with_RasterImageExt_Object():
     assert f.extensions["raster-image-ext"].exif_tags["XResolution"] == 4928
 
 
+def test_file_with_archive_ext_object():
+    ad = stix2.v21.Directory(path="archived/path")
+    f_obj = stix2.v21.File(
+        name="foo", extensions={
+            "archive-ext": {
+                "contains_refs": [ad, ],
+            },
+        },
+    )
+    f_ref = stix2.v21.File(
+        name="foo", extensions={
+            "archive-ext": {
+                "contains_refs": [ad.id, ],
+            },
+        },
+    )
+
+    assert f_obj["id"] == f_ref["id"]
+    assert f_obj["extensions"]["archive-ext"]["contains_refs"][0] == ad["id"]
+
+
 RASTER_IMAGE_EXT = """{
 "type": "observed-data",
 "spec_version": "2.1",
@@ -1469,133 +1489,3 @@ def test_objects_deprecation():
                 },
             },
         )
-
-
-def test_deterministic_id_same_extra_prop_vals():
-    email_addr_1 = stix2.v21.EmailAddress(
-        value="john@example.com",
-        display_name="Johnny Doe",
-    )
-
-    email_addr_2 = stix2.v21.EmailAddress(
-        value="john@example.com",
-        display_name="Johnny Doe",
-    )
-
-    assert email_addr_1.id == email_addr_2.id
-
-    uuid_obj_1 = uuid.UUID(email_addr_1.id[-36:])
-    assert uuid_obj_1.variant == uuid.RFC_4122
-    assert uuid_obj_1.version == 5
-
-    uuid_obj_2 = uuid.UUID(email_addr_2.id[-36:])
-    assert uuid_obj_2.variant == uuid.RFC_4122
-    assert uuid_obj_2.version == 5
-
-
-def test_deterministic_id_diff_extra_prop_vals():
-    email_addr_1 = stix2.v21.EmailAddress(
-        value="john@example.com",
-        display_name="Johnny Doe",
-    )
-
-    email_addr_2 = stix2.v21.EmailAddress(
-        value="john@example.com",
-        display_name="Janey Doe",
-    )
-
-    assert email_addr_1.id == email_addr_2.id
-
-    uuid_obj_1 = uuid.UUID(email_addr_1.id[-36:])
-    assert uuid_obj_1.variant == uuid.RFC_4122
-    assert uuid_obj_1.version == 5
-
-    uuid_obj_2 = uuid.UUID(email_addr_2.id[-36:])
-    assert uuid_obj_2.variant == uuid.RFC_4122
-    assert uuid_obj_2.version == 5
-
-
-def test_deterministic_id_diff_contributing_prop_vals():
-    email_addr_1 = stix2.v21.EmailAddress(
-        value="john@example.com",
-        display_name="Johnny Doe",
-    )
-
-    email_addr_2 = stix2.v21.EmailAddress(
-        value="jane@example.com",
-        display_name="Janey Doe",
-    )
-
-    assert email_addr_1.id != email_addr_2.id
-
-    uuid_obj_1 = uuid.UUID(email_addr_1.id[-36:])
-    assert uuid_obj_1.variant == uuid.RFC_4122
-    assert uuid_obj_1.version == 5
-
-    uuid_obj_2 = uuid.UUID(email_addr_2.id[-36:])
-    assert uuid_obj_2.variant == uuid.RFC_4122
-    assert uuid_obj_2.version == 5
-
-
-def test_deterministic_id_no_contributing_props():
-    email_msg_1 = stix2.v21.EmailMessage(
-        is_multipart=False,
-    )
-
-    email_msg_2 = stix2.v21.EmailMessage(
-        is_multipart=False,
-    )
-
-    assert email_msg_1.id != email_msg_2.id
-
-    uuid_obj_1 = uuid.UUID(email_msg_1.id[-36:])
-    assert uuid_obj_1.variant == uuid.RFC_4122
-    assert uuid_obj_1.version == 4
-
-    uuid_obj_2 = uuid.UUID(email_msg_2.id[-36:])
-    assert uuid_obj_2.variant == uuid.RFC_4122
-    assert uuid_obj_2.version == 4
-
-
-def test_id_gen_recursive_dict_conversion_1():
-    file_observable = stix2.v21.File(
-        name="example.exe",
-        size=68 * 1000,
-        magic_number_hex="50000000",
-        hashes={
-            "SHA-256": "841a8921140aba50671ebb0770fecc4ee308c4952cfeff8de154ab14eeef4649",
-        },
-        extensions={
-            "windows-pebinary-ext": stix2.v21.WindowsPEBinaryExt(
-                pe_type="exe",
-                machine_hex="014c",
-                sections=[
-                    stix2.v21.WindowsPESection(
-                        name=".data",
-                        size=4096,
-                        entropy=7.980693,
-                        hashes={"SHA-256": "6e3b6f3978e5cd96ba7abee35c24e867b7e64072e2ecb22d0ee7a6e6af6894d0"},
-                    ),
-                ],
-            ),
-        },
-    )
-
-    assert file_observable.id == "file--ced31cd4-bdcb-537d-aefa-92d291bfc11d"
-
-
-def test_id_gen_recursive_dict_conversion_2():
-    wrko = stix2.v21.WindowsRegistryKey(
-        values=[
-            stix2.v21.WindowsRegistryValueType(
-                name="Foo",
-                data="qwerty",
-            ),
-            stix2.v21.WindowsRegistryValueType(
-                name="Bar",
-                data="42",
-            ),
-        ],
-    )
-
-    assert wrko.id == "windows-registry-key--36594eba-bcc7-5014-9835-0e154264e588"
diff --git a/stix2/test/v21/test_versioning.py b/stix2/test/v21/test_versioning.py
index bee0c07..adfa7a0 100644
--- a/stix2/test/v21/test_versioning.py
+++ b/stix2/test/v21/test_versioning.py
@@ -3,7 +3,10 @@ import datetime
 import pytest
 
 import stix2
+import stix2.exceptions
 import stix2.utils
+import stix2.v21
+import stix2.versioning
 
 from .constants import CAMPAIGN_MORE_KWARGS
 
@@ -151,7 +154,7 @@ def test_versioning_error_revoke_of_revoked():
 
 def test_making_new_version_dict():
     campaign_v1 = CAMPAIGN_MORE_KWARGS
-    campaign_v2 = stix2.utils.new_version(CAMPAIGN_MORE_KWARGS, name="fred")
+    campaign_v2 = stix2.versioning.new_version(CAMPAIGN_MORE_KWARGS, name="fred")
 
     assert campaign_v1['id'] == campaign_v2['id']
     assert campaign_v1['spec_version'] == campaign_v2['spec_version']
@@ -165,7 +168,7 @@ def test_making_new_version_dict():
 
 def test_versioning_error_dict_bad_modified_value():
     with pytest.raises(stix2.exceptions.InvalidValueError) as excinfo:
-        stix2.utils.new_version(CAMPAIGN_MORE_KWARGS, modified="2015-04-06T20:03:00.000Z")
+        stix2.versioning.new_version(CAMPAIGN_MORE_KWARGS, modified="2015-04-06T20:03:00.000Z")
 
     assert excinfo.value.cls == dict
     assert excinfo.value.prop_name == "modified"
@@ -181,7 +184,7 @@ def test_versioning_error_dict_no_modified_value():
         'created': "2016-04-06T20:03:00.000Z",
         'name': "Green Group Attacks Against Finance",
     }
-    campaign_v2 = stix2.utils.new_version(campaign_v1, modified="2017-04-06T20:03:00.000Z")
+    campaign_v2 = stix2.versioning.new_version(campaign_v1, modified="2017-04-06T20:03:00.000Z")
 
     assert str(campaign_v2['modified']) == "2017-04-06T20:03:00.000Z"
 
@@ -189,14 +192,14 @@ def test_versioning_error_dict_no_modified_value():
 def test_making_new_version_invalid_cls():
     campaign_v1 = "This is a campaign."
     with pytest.raises(ValueError) as excinfo:
-        stix2.utils.new_version(campaign_v1, name="fred")
+        stix2.versioning.new_version(campaign_v1, name="fred")
 
     assert 'cannot create new version of object of this type' in str(excinfo.value)
 
 
 def test_revoke_dict():
     campaign_v1 = CAMPAIGN_MORE_KWARGS
-    campaign_v2 = stix2.utils.revoke(campaign_v1)
+    campaign_v2 = stix2.versioning.revoke(campaign_v1)
 
     assert campaign_v1['id'] == campaign_v2['id']
     assert campaign_v1['spec_version'] == campaign_v2['spec_version']
@@ -209,12 +212,18 @@ def test_revoke_dict():
     assert campaign_v2['revoked']
 
 
+def test_revoke_unversionable():
+    sco = stix2.v21.File(name="data.txt")
+    with pytest.raises(ValueError):
+        sco.revoke()
+
+
 def test_versioning_error_revoke_of_revoked_dict():
     campaign_v1 = CAMPAIGN_MORE_KWARGS
-    campaign_v2 = stix2.utils.revoke(campaign_v1)
+    campaign_v2 = stix2.versioning.revoke(campaign_v1)
 
     with pytest.raises(stix2.exceptions.RevokeError) as excinfo:
-        stix2.utils.revoke(campaign_v2)
+        stix2.versioning.revoke(campaign_v2)
 
     assert excinfo.value.called_by == "revoke"
 
@@ -222,7 +231,7 @@ def test_versioning_error_revoke_of_revoked_dict():
 def test_revoke_invalid_cls():
     campaign_v1 = "This is a campaign."
     with pytest.raises(ValueError) as excinfo:
-        stix2.utils.revoke(campaign_v1)
+        stix2.versioning.revoke(campaign_v1)
 
     assert 'cannot revoke object of this type' in str(excinfo.value)
 
@@ -236,7 +245,7 @@ def test_remove_custom_stix_property():
         is_family=False,
     )
 
-    mal_nc = stix2.utils.remove_custom_stix(mal)
+    mal_nc = stix2.versioning.remove_custom_stix(mal)
 
     assert "x_custom" not in mal_nc
     assert mal["modified"] < mal_nc["modified"]
@@ -254,14 +263,14 @@ def test_remove_custom_stix_object():
 
     animal = Animal(species="lion", animal_class="mammal")
 
-    nc = stix2.utils.remove_custom_stix(animal)
+    nc = stix2.versioning.remove_custom_stix(animal)
 
     assert nc is None
 
 
 def test_remove_custom_stix_no_custom():
     campaign_v1 = stix2.v21.Campaign(**CAMPAIGN_MORE_KWARGS)
-    campaign_v2 = stix2.utils.remove_custom_stix(campaign_v1)
+    campaign_v2 = stix2.versioning.remove_custom_stix(campaign_v1)
 
     assert len(campaign_v1.keys()) == len(campaign_v2.keys())
     assert campaign_v1.id == campaign_v2.id
@@ -294,5 +303,96 @@ def test_fudge_modified(old, candidate_new, expected_new, use_stix21):
         expected_new, "%Y-%m-%dT%H:%M:%S.%fZ",
     )
 
-    fudged = stix2.utils._fudge_modified(old_dt, candidate_new_dt, use_stix21)
+    fudged = stix2.versioning._fudge_modified(
+        old_dt, candidate_new_dt, use_stix21,
+    )
     assert fudged == expected_new_dt
+
+
+def test_version_unversionable_dict():
+    f = {
+        "type": "file",
+        "id": "file--4efb5217-e987-4438-9a1b-c800099401df",
+        "name": "data.txt",
+    }
+
+    with pytest.raises(ValueError):
+        stix2.versioning.new_version(f)
+
+
+def test_version_sco_with_custom():
+    """
+    If we add custom properties named like versioning properties to an object
+    type which is otherwise unversionable, versioning should start working.
+    """
+
+    file_sco_obj = stix2.v21.File(
+        name="data.txt",
+        created="1973-11-23T02:31:37Z",
+        modified="1991-05-13T19:24:57Z",
+        revoked=False,
+        allow_custom=True,
+    )
+
+    new_file_sco_obj = stix2.versioning.new_version(
+        file_sco_obj, size=1234,
+    )
+
+    assert new_file_sco_obj.size == 1234
+
+    revoked_obj = stix2.versioning.revoke(new_file_sco_obj)
+    assert revoked_obj.revoked
+
+
+def test_version_disable_custom():
+    m = stix2.v21.Malware(
+        name="foo", description="Steals your identity!", is_family=False,
+        x_custom=123, allow_custom=True,
+    )
+
+    # Remove the custom property, and disallow custom properties in the
+    # resulting object.
+    m2 = stix2.versioning.new_version(m, x_custom=None, allow_custom=False)
+    assert "x_custom" not in m2
+
+    # Remove a regular property and leave the custom one, disallow custom
+    # properties, and make sure we get an error.
+    with pytest.raises(stix2.exceptions.ExtraPropertiesError):
+        stix2.versioning.new_version(m, description=None, allow_custom=False)
+
+
+def test_version_enable_custom():
+    m = stix2.v21.Malware(
+        name="foo", description="Steals your identity!", is_family=False,
+    )
+
+    # Add a custom property to an object for which it was previously disallowed
+    m2 = stix2.versioning.new_version(m, x_custom=123, allow_custom=True)
+    assert "x_custom" in m2
+
+    # Add a custom property without enabling it, make sure we get an error
+    with pytest.raises(stix2.exceptions.ExtraPropertiesError):
+        stix2.versioning.new_version(m, x_custom=123, allow_custom=False)
+
+
+def test_version_propagate_custom():
+    m = stix2.v21.Malware(
+        name="foo", is_family=False,
+    )
+
+    # Remember custom-not-allowed setting from original; produce error
+    with pytest.raises(stix2.exceptions.ExtraPropertiesError):
+        stix2.versioning.new_version(m, x_custom=123)
+
+    m2 = stix2.versioning.new_version(m, description="Steals your identity!")
+    assert "description" in m2
+    assert m2.description == "Steals your identity!"
+
+    m_custom = stix2.v21.Malware(
+        name="foo", is_family=False, x_custom=123, allow_custom=True,
+    )
+
+    # Remember custom-allowed setting from original; should work
+    m2_custom = stix2.versioning.new_version(m_custom, x_other_custom="abc")
+    assert "x_other_custom" in m2_custom
+    assert m2_custom.x_other_custom == "abc"
diff --git a/stix2/utils.py b/stix2/utils.py
index 766fd4b..7a8d8cb 100644
--- a/stix2/utils.py
+++ b/stix2/utils.py
@@ -1,10 +1,5 @@
 """Utility functions and classes for the STIX2 library."""
 
-try:
-    from collections.abc import Mapping
-except ImportError:
-    from collections import Mapping
-import copy
 import datetime as dt
 import enum
 import json
@@ -15,20 +10,11 @@ import six
 
 import stix2
 
-from .exceptions import (
-    InvalidValueError, RevokeError, UnmodifiablePropertyError,
-)
-
 # Sentinel value for properties that should be set to the current time.
 # We can't use the standard 'default' approach, since if there are multiple
 # timestamps in a single object, the timestamps will vary by a few microseconds.
 NOW = object()
 
-# STIX object properties that cannot be modified
-STIX_UNMOD_PROPERTIES = ['created', 'created_by_ref', 'id', 'type']
-
-TYPE_REGEX = re.compile(r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-?$')
-TYPE_21_REGEX = re.compile(r'^([a-z][a-z0-9]*)+(-[a-z0-9]+)*\-?$')
 PREFIX_21_REGEX = re.compile(r'^[a-z].*')
 
 _TIMESTAMP_FORMAT = "%Y-%m-%dT%H:%M:%SZ"
@@ -389,121 +375,6 @@ def find_property_index(obj, search_key, search_value):
     return idx
 
 
-def _fudge_modified(old_modified, new_modified, use_stix21):
-    """
-    Ensures a new modified timestamp is newer than the old.  When they are
-    too close together, new_modified must be pushed further ahead to ensure
-    it is distinct and later, after JSON serialization (which may mean it's
-    actually being pushed a little ways into the future).  JSON serialization
-    can remove precision, which can cause distinct timestamps to accidentally
-    become equal, if we're not careful.
-
-    :param old_modified: A previous "modified" timestamp, as a datetime object
-    :param new_modified: A candidate new "modified" timestamp, as a datetime
-        object
-    :param use_stix21: Whether to use STIX 2.1+ versioning timestamp precision
-        rules (boolean).  This is important so that we are aware of how
-        timestamp precision will be truncated, so we know how close together
-        the timestamps can be, and how far ahead to potentially push the new
-        one.
-    :return: A suitable new "modified" timestamp.  This may be different from
-        what was passed in, if it had to be pushed ahead.
-    """
-    if use_stix21:
-        # 2.1+: we can use full precision
-        if new_modified <= old_modified:
-            new_modified = old_modified + dt.timedelta(microseconds=1)
-    else:
-        # 2.0: we must use millisecond precision
-        one_ms = dt.timedelta(milliseconds=1)
-        if new_modified - old_modified < one_ms:
-            new_modified = old_modified + one_ms
-
-    return new_modified
-
-
-def new_version(data, **kwargs):
-    """Create a new version of a STIX object, by modifying properties and
-    updating the ``modified`` property.
-    """
-
-    if not isinstance(data, Mapping):
-        raise ValueError(
-            "cannot create new version of object of this type! "
-            "Try a dictionary or instance of an SDO or SRO class.",
-        )
-
-    unchangable_properties = []
-    if data.get('revoked'):
-        raise RevokeError("new_version")
-    try:
-        new_obj_inner = copy.deepcopy(data._inner)
-    except AttributeError:
-        new_obj_inner = copy.deepcopy(data)
-    properties_to_change = kwargs.keys()
-
-    # Make sure certain properties aren't trying to change
-    for prop in STIX_UNMOD_PROPERTIES:
-        if prop in properties_to_change:
-            unchangable_properties.append(prop)
-    if unchangable_properties:
-        raise UnmodifiablePropertyError(unchangable_properties)
-
-    # Different versioning precision rules in STIX 2.0 vs 2.1, so we need
-    # to know which rules to apply.
-    is_21 = "spec_version" in data
-    precision_constraint = "min" if is_21 else "exact"
-
-    cls = type(data)
-    if 'modified' not in kwargs:
-        old_modified = parse_into_datetime(
-            data["modified"], precision="millisecond",
-            precision_constraint=precision_constraint,
-        )
-
-        new_modified = get_timestamp()
-        new_modified = _fudge_modified(old_modified, new_modified, is_21)
-
-        kwargs['modified'] = new_modified
-
-    elif 'modified' in data:
-        old_modified_property = parse_into_datetime(
-            data.get('modified'), precision='millisecond',
-            precision_constraint=precision_constraint,
-        )
-        new_modified_property = parse_into_datetime(
-            kwargs['modified'], precision='millisecond',
-            precision_constraint=precision_constraint,
-        )
-        if new_modified_property <= old_modified_property:
-            raise InvalidValueError(
-                cls, 'modified',
-                "The new modified datetime cannot be before than or equal to the current modified datetime."
-                "It cannot be equal, as according to STIX 2 specification, objects that are different "
-                "but have the same id and modified timestamp do not have defined consumer behavior.",
-            )
-    new_obj_inner.update(kwargs)
-    # Exclude properties with a value of 'None' in case data is not an instance of a _STIXBase subclass
-    return cls(**{k: v for k, v in new_obj_inner.items() if v is not None})
-
-
-def revoke(data):
-    """Revoke a STIX object.
-
-    Returns:
-        A new version of the object with ``revoked`` set to ``True``.
-    """
-    if not isinstance(data, Mapping):
-        raise ValueError(
-            "cannot revoke object of this type! Try a dictionary "
-            "or instance of an SDO or SRO class.",
-        )
-
-    if data.get('revoked'):
-        raise RevokeError("revoke")
-    return new_version(data, revoked=True, allow_custom=True)
-
-
 def get_class_hierarchy_names(obj):
     """Given an object, return the names of the class hierarchy."""
     names = []
@@ -512,64 +383,6 @@ def get_class_hierarchy_names(obj):
     return names
 
 
-def remove_custom_stix(stix_obj):
-    """Remove any custom STIX objects or properties.
-
-    Warnings:
-        This function is a best effort utility, in that it will remove custom
-        objects and properties based on the type names; i.e. if "x-" prefixes
-        object types, and "x\\_" prefixes property types. According to the
-        STIX2 spec, those naming conventions are a SHOULDs not MUSTs, meaning
-        that valid custom STIX content may ignore those conventions and in
-        effect render this utility function invalid when used on that STIX
-        content.
-
-    Args:
-        stix_obj (dict OR python-stix obj): a single python-stix object
-                                             or dict of a STIX object
-
-    Returns:
-        A new version of the object with any custom content removed
-    """
-
-    if stix_obj['type'].startswith('x-'):
-        # if entire object is custom, discard
-        return None
-
-    custom_props = []
-    for prop in stix_obj.items():
-        if prop[0].startswith('x_'):
-            # for every custom property, record it and set value to None
-            # (so we can pass it to new_version() and it will be dropped)
-            custom_props.append((prop[0], None))
-
-    if custom_props:
-        # obtain set of object properties that can be transferred
-        # to a new object version. This is 1)custom props with their
-        # values set to None, and 2)any properties left that are not
-        # unmodifiable STIX properties or the "modified" property
-
-        # set of properties that are not supplied to new_version()
-        # to be used for updating properties. This includes unmodifiable
-        # properties (properties that new_version() just re-uses from the
-        # existing STIX object) and the "modified" property. We dont supply the
-        # "modified" property so that new_version() creates a new datetime
-        # value for this property
-        non_supplied_props = STIX_UNMOD_PROPERTIES + ['modified']
-
-        props = [(prop, stix_obj[prop]) for prop in stix_obj if prop not in non_supplied_props]
-
-        # add to set the custom properties we want to get rid of (with their value=None)
-        props.extend(custom_props)
-
-        new_obj = new_version(stix_obj, **(dict(props)))
-
-        return new_obj
-
-    else:
-        return stix_obj
-
-
 def get_type_from_id(stix_id):
     return stix_id.split('--', 1)[0]
 
diff --git a/stix2/v20/__init__.py b/stix2/v20/__init__.py
index b77d46c..36d09be 100644
--- a/stix2/v20/__init__.py
+++ b/stix2/v20/__init__.py
@@ -103,3 +103,33 @@ EXT_MAP = {
         'unix-account-ext': UNIXAccountExt,
     },
 }
+
+
+# Ensure star-imports from this module get the right symbols.  "base" is a
+# known problem, since there are multiple modules with that name and one can
+# accidentally overwrite another.
+__all__ = """
+    Bundle,
+
+    TLP_AMBER, TLP_GREEN, TLP_RED, TLP_WHITE, CustomMarking, ExternalReference,
+    GranularMarking, KillChainPhase, MarkingDefinition, StatementMarking,
+    TLPMarking,
+
+    URL, AlternateDataStream, ArchiveExt, Artifact, AutonomousSystem,
+    CustomExtension, CustomObservable, Directory, DomainName, EmailAddress,
+    EmailMessage, EmailMIMEComponent, File, HTTPRequestExt, ICMPExt,
+    IPv4Address, IPv6Address, MACAddress, Mutex, NetworkTraffic, NTFSExt,
+    PDFExt, Process, RasterImageExt, SocketExt, Software, TCPExt,
+    UNIXAccountExt, UserAccount, WindowsPEBinaryExt,
+    WindowsPEOptionalHeaderType, WindowsPESection, WindowsProcessExt,
+    WindowsRegistryKey, WindowsRegistryValueType, WindowsServiceExt,
+    X509Certificate, X509V3ExtenstionsType,
+
+    AttackPattern, Campaign, CourseOfAction, CustomObject, Identity, Indicator,
+    IntrusionSet, Malware, ObservedData, Report, ThreatActor, Tool,
+    Vulnerability,
+
+    Relationship, Sighting,
+
+    OBJ_MAP, OBJ_MAP_OBSERVABLE, EXT_MAP
+""".replace(",", " ").split()
diff --git a/stix2/v21/__init__.py b/stix2/v21/__init__.py
index eea61dd..77a28ee 100644
--- a/stix2/v21/__init__.py
+++ b/stix2/v21/__init__.py
@@ -111,3 +111,34 @@ EXT_MAP = {
         'unix-account-ext': UNIXAccountExt,
     },
 }
+
+
+# Ensure star-imports from this module get the right symbols.  "base" is a
+# known problem, since there are multiple modules with that name and one can
+# accidentally overwrite another.
+__all__ = """
+    Bundle,
+
+    TLP_AMBER, TLP_GREEN, TLP_RED, TLP_WHITE, CustomMarking, ExternalReference,
+    GranularMarking, KillChainPhase, LanguageContent, MarkingDefinition,
+    StatementMarking, TLPMarking,
+
+    URL, AlternateDataStream, ArchiveExt, Artifact, AutonomousSystem,
+    CustomExtension, CustomObservable, Directory, DomainName, EmailAddress,
+    EmailMessage, EmailMIMEComponent, File, HTTPRequestExt, ICMPExt,
+    IPv4Address, IPv6Address, MACAddress, Mutex, NetworkTraffic, NTFSExt,
+    PDFExt, Process, RasterImageExt, SocketExt, Software, TCPExt,
+    UNIXAccountExt, UserAccount, WindowsPEBinaryExt,
+    WindowsPEOptionalHeaderType, WindowsPESection, WindowsProcessExt,
+    WindowsRegistryKey, WindowsRegistryValueType, WindowsServiceExt,
+    X509Certificate, X509V3ExtenstionsType,
+
+    AttackPattern, Campaign, CourseOfAction, CustomObject, Grouping, Identity,
+    Indicator, Infrastructure, IntrusionSet, Location, Malware,
+    MalwareAnalysis, Note, ObservedData, Opinion, Report, ThreatActor, Tool,
+    Vulnerability,
+
+    Relationship, Sighting,
+
+    OBJ_MAP, OBJ_MAP_OBSERVABLE, EXT_MAP
+""".replace(",", " ").split()
diff --git a/stix2/v21/observables.py b/stix2/v21/observables.py
index d73c1cf..a15d5bd 100644
--- a/stix2/v21/observables.py
+++ b/stix2/v21/observables.py
@@ -14,8 +14,7 @@ from ..properties import (
     BinaryProperty, BooleanProperty, DictionaryProperty,
     EmbeddedObjectProperty, EnumProperty, ExtensionsProperty, FloatProperty,
     HashesProperty, HexProperty, IDProperty, IntegerProperty, ListProperty,
-    ObjectReferenceProperty, ReferenceProperty, StringProperty,
-    TimestampProperty, TypeProperty,
+    ReferenceProperty, StringProperty, TimestampProperty, TypeProperty,
 )
 from .base import _Extension, _Observable, _STIXBase21
 from .common import GranularMarking
@@ -144,7 +143,7 @@ class EmailMIMEComponent(_STIXBase21):
 
     _properties = OrderedDict([
         ('body', StringProperty()),
-        ('body_raw_ref', ObjectReferenceProperty(valid_types=['artifact', 'file'])),
+        ('body_raw_ref', ReferenceProperty(valid_types=['artifact', 'file'], spec_version="2.1")),
         ('content_type', StringProperty()),
         ('content_disposition', StringProperty()),
     ])
@@ -201,7 +200,7 @@ class ArchiveExt(_Extension):
 
     _type = 'archive-ext'
     _properties = OrderedDict([
-        ('contains_refs', ListProperty(ObjectReferenceProperty(valid_types=['file', 'directory']), required=True)),
+        ('contains_refs', ListProperty(ReferenceProperty(valid_types=['file', 'directory'], spec_version="2.1"), required=True)),
         ('comment', StringProperty()),
     ])
 
@@ -465,7 +464,7 @@ class HTTPRequestExt(_Extension):
         ('request_version', StringProperty()),
         ('request_header', DictionaryProperty(spec_version='2.1')),
         ('message_body_length', IntegerProperty()),
-        ('message_body_data_ref', ObjectReferenceProperty(valid_types='artifact')),
+        ('message_body_data_ref', ReferenceProperty(valid_types='artifact', spec_version="2.1")),
     ])
 
 
@@ -654,7 +653,7 @@ class WindowsServiceExt(_Extension):
                 "SERVICE_SYSTEM_ALERT",
             ]),
         ),
-        ('service_dll_refs', ListProperty(ObjectReferenceProperty(valid_types='file'))),
+        ('service_dll_refs', ListProperty(ReferenceProperty(valid_types='file', spec_version="2.1"))),
         (
             'service_type', EnumProperty(allowed=[
                 "SERVICE_KERNEL_DRIVER",
diff --git a/stix2/versioning.py b/stix2/versioning.py
new file mode 100644
index 0000000..8db8f7a
--- /dev/null
+++ b/stix2/versioning.py
@@ -0,0 +1,275 @@
+import copy
+import datetime as dt
+import itertools
+import uuid
+
+import six
+from six.moves.collections_abc import Mapping
+
+import stix2.base
+from stix2.utils import get_timestamp, parse_into_datetime
+import stix2.v20
+
+from .exceptions import (
+    InvalidValueError, RevokeError, UnmodifiablePropertyError,
+)
+
+# STIX object properties that cannot be modified
+STIX_UNMOD_PROPERTIES = ['created', 'created_by_ref', 'id', 'type']
+_VERSIONING_PROPERTIES = {"created", "modified", "revoked"}
+
+
+def _fudge_modified(old_modified, new_modified, use_stix21):
+    """
+    Ensures a new modified timestamp is newer than the old.  When they are
+    too close together, new_modified must be pushed further ahead to ensure
+    it is distinct and later, after JSON serialization (which may mean it's
+    actually being pushed a little ways into the future).  JSON serialization
+    can remove precision, which can cause distinct timestamps to accidentally
+    become equal, if we're not careful.
+
+    :param old_modified: A previous "modified" timestamp, as a datetime object
+    :param new_modified: A candidate new "modified" timestamp, as a datetime
+        object
+    :param use_stix21: Whether to use STIX 2.1+ versioning timestamp precision
+        rules (boolean).  This is important so that we are aware of how
+        timestamp precision will be truncated, so we know how close together
+        the timestamps can be, and how far ahead to potentially push the new
+        one.
+    :return: A suitable new "modified" timestamp.  This may be different from
+        what was passed in, if it had to be pushed ahead.
+    """
+    if use_stix21:
+        # 2.1+: we can use full precision
+        if new_modified <= old_modified:
+            new_modified = old_modified + dt.timedelta(microseconds=1)
+    else:
+        # 2.0: we must use millisecond precision
+        one_ms = dt.timedelta(milliseconds=1)
+        if new_modified - old_modified < one_ms:
+            new_modified = old_modified + one_ms
+
+    return new_modified
+
+
+def _is_versionable(data):
+    """
+    Determine whether the given object is versionable.  This check is done on
+    the basis of support for three properties for the object type: "created",
+    "modified", and "revoked".  If all three are supported, the object is
+    versionable; otherwise it is not.  Dicts must have a "type" property whose
+    value is for a registered object type.  This is used to determine a
+    complete set of supported properties for the type.
+
+    Also, detect whether it represents a STIX 2.1 or greater spec version.
+
+    :param data: The object to check.  Must be either a stix object, or a dict
+        with a "type" property.
+    :return: A 2-tuple of bools: the first is True if the object is versionable
+        and False if not; the second is True if the object is STIX 2.1+ and
+        False if not.
+    """
+
+    is_versionable = False
+    is_21 = False
+    stix_vid = None
+
+    if isinstance(data, Mapping):
+
+        # First, determine spec version.  It's easy for our stix2 objects; more
+        # work for dicts.
+        is_21 = False
+        if isinstance(data, stix2.base._STIXBase) and \
+                not isinstance(data, stix2.v20._STIXBase20):
+            # (is_21 means 2.1 or later; try not to be 2.1-specific)
+            is_21 = True
+        elif isinstance(data, dict):
+            stix_vid = stix2.parsing._detect_spec_version(data)
+            is_21 = stix_vid != "v20"
+
+        # Then, determine versionability.
+
+        if six.PY2:
+            # dumb python2 compatibility: map.keys() returns a list, not a set!
+            # six.viewkeys() compatibility function uses dict.viewkeys() on
+            # python2, which is not a Mapping mixin method, so that doesn't
+            # work either (for our stix2 objects).
+            keys = set(data)
+        else:
+            keys = data.keys()
+
+        # This should be sufficient for STIX objects; maybe we get lucky with
+        # dicts here but probably not.
+        if keys >= _VERSIONING_PROPERTIES:
+            is_versionable = True
+
+        # Tougher to handle dicts.  We need to consider STIX version, map to a
+        # registered class, and from that get a more complete picture of its
+        # properties.
+        elif isinstance(data, dict):
+            class_maps = stix2.parsing.STIX2_OBJ_MAPS[stix_vid]
+            obj_type = data["type"]
+
+            if obj_type in class_maps["objects"]:
+                # Should we bother checking properties for SDOs/SROs?
+                # They were designed to be versionable.
+                is_versionable = True
+
+            elif obj_type in class_maps["observables"]:
+                # but do check SCOs
+                cls = class_maps["observables"][obj_type]
+                is_versionable = _VERSIONING_PROPERTIES.issubset(
+                    cls._properties,
+                )
+
+    return is_versionable, is_21
+
+
+def new_version(data, allow_custom=None, **kwargs):
+    """
+    Create a new version of a STIX object, by modifying properties and
+    updating the ``modified`` property.
+
+    :param data: The object to create a new version of.  Maybe a stix2 object
+        or dict.
+    :param allow_custom: Whether to allow custom properties on the new object.
+        If True, allow them (regardless of whether the original had custom
+        properties); if False disallow them; if None, propagate the preference
+        from the original object.
+    :param kwargs: The properties to change.  Setting to None requests property
+        removal.
+    :return: The new object.
+    """
+
+    is_versionable, is_21 = _is_versionable(data)
+
+    if not is_versionable:
+        raise ValueError(
+            "cannot create new version of object of this type! "
+            "Try a dictionary or instance of an SDO or SRO class.",
+        )
+
+    if data.get('revoked'):
+        raise RevokeError("new_version")
+    try:
+        new_obj_inner = copy.deepcopy(data._inner)
+    except AttributeError:
+        new_obj_inner = copy.deepcopy(data)
+
+    # Make sure certain properties aren't trying to change
+    # ID contributing properties of 2.1+ SCOs may also not change if a UUIDv5
+    # is in use (depending on whether they were used to create it... but they
+    # probably were).  That would imply an ID change, which is not allowed
+    # across versions.
+    sco_locked_props = []
+    if is_21 and isinstance(data, stix2.base._Observable):
+        uuid_ = uuid.UUID(data["id"][-36:])
+        if uuid_.variant == uuid.RFC_4122 and uuid_.version == 5:
+            sco_locked_props = data._id_contributing_properties
+
+    unchangable_properties = set()
+    for prop in itertools.chain(STIX_UNMOD_PROPERTIES, sco_locked_props):
+        if prop in kwargs:
+            unchangable_properties.add(prop)
+    if unchangable_properties:
+        raise UnmodifiablePropertyError(unchangable_properties)
+
+    # Different versioning precision rules in STIX 2.0 vs 2.1, so we need
+    # to know which rules to apply.
+    precision_constraint = "min" if is_21 else "exact"
+
+    cls = type(data)
+    if 'modified' not in kwargs:
+        old_modified = parse_into_datetime(
+            data["modified"], precision="millisecond",
+            precision_constraint=precision_constraint,
+        )
+
+        new_modified = get_timestamp()
+        new_modified = _fudge_modified(old_modified, new_modified, is_21)
+
+        kwargs['modified'] = new_modified
+
+    elif 'modified' in data:
+        old_modified_property = parse_into_datetime(
+            data.get('modified'), precision='millisecond',
+            precision_constraint=precision_constraint,
+        )
+        new_modified_property = parse_into_datetime(
+            kwargs['modified'], precision='millisecond',
+            precision_constraint=precision_constraint,
+        )
+        if new_modified_property <= old_modified_property:
+            raise InvalidValueError(
+                cls, 'modified',
+                "The new modified datetime cannot be before than or equal to the current modified datetime."
+                "It cannot be equal, as according to STIX 2 specification, objects that are different "
+                "but have the same id and modified timestamp do not have defined consumer behavior.",
+            )
+    new_obj_inner.update(kwargs)
+
+    # Set allow_custom appropriately if versioning an object.  We will ignore
+    # it for dicts.
+    if isinstance(data, stix2.base._STIXBase):
+        if allow_custom is None:
+            new_obj_inner["allow_custom"] = data._allow_custom
+        else:
+            new_obj_inner["allow_custom"] = allow_custom
+
+    # Exclude properties with a value of 'None' in case data is not an instance of a _STIXBase subclass
+    return cls(**{k: v for k, v in new_obj_inner.items() if v is not None})
+
+
+def revoke(data):
+    """Revoke a STIX object.
+
+    Returns:
+        A new version of the object with ``revoked`` set to ``True``.
+    """
+    if not isinstance(data, Mapping):
+        raise ValueError(
+            "cannot revoke object of this type! Try a dictionary "
+            "or instance of an SDO or SRO class.",
+        )
+
+    if data.get('revoked'):
+        raise RevokeError("revoke")
+    return new_version(data, revoked=True)
+
+
+def remove_custom_stix(stix_obj):
+    """Remove any custom STIX objects or properties.
+
+    Warnings:
+        This function is a best effort utility, in that it will remove custom
+        objects and properties based on the type names; i.e. if "x-" prefixes
+        object types, and "x\\_" prefixes property types. According to the
+        STIX2 spec, those naming conventions are a SHOULDs not MUSTs, meaning
+        that valid custom STIX content may ignore those conventions and in
+        effect render this utility function invalid when used on that STIX
+        content.
+
+    Args:
+        stix_obj (dict OR python-stix obj): a single python-stix object
+                                             or dict of a STIX object
+
+    Returns:
+        A new version of the object with any custom content removed
+    """
+
+    if stix_obj['type'].startswith('x-'):
+        # if entire object is custom, discard
+        return None
+
+    custom_props = {
+        k: None
+        for k in stix_obj if k.startswith("x_")
+    }
+
+    if custom_props:
+        new_obj = new_version(stix_obj, allow_custom=False, **custom_props)
+
+        return new_obj
+
+    else:
+        return stix_obj