diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index 197bcb8..c74d90d 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -6,6 +6,7 @@
 
 import calendar
 import collections
+import datetime
 import itertools
 from contextlib import contextmanager
 
@@ -1941,6 +1942,52 @@
         assert res == 1
         return self._read_mem_bio(bio)
 
+    def _asn1_integer_to_int(self, asn1_int):
+        bn = self._lib.ASN1_INTEGER_to_BN(asn1_int, self._ffi.NULL)
+        assert bn != self._ffi.NULL
+        bn = self._ffi.gc(bn, self._lib.BN_free)
+        return self._bn_to_int(bn)
+
+    def _asn1_string_to_bytes(self, asn1_string):
+        return self._ffi.buffer(asn1_string.data, asn1_string.length)[:]
+
+    def _asn1_string_to_ascii(self, asn1_string):
+        return self._asn1_string_to_bytes(asn1_string).decode("ascii")
+
+    def _asn1_string_to_utf8(self, asn1_string):
+        buf = self._ffi.new("unsigned char **")
+        res = self._lib.ASN1_STRING_to_UTF8(buf, asn1_string)
+        assert res >= 0
+        assert buf[0] != self._ffi.NULL
+        buf = self._ffi.gc(
+            buf, lambda buffer: self._lib.OPENSSL_free(buffer[0])
+        )
+        return self._ffi.buffer(buf[0], res)[:].decode('utf8')
+
+    def _asn1_to_der(self, asn1_type):
+        buf = self._ffi.new("unsigned char **")
+        res = self._lib.i2d_ASN1_TYPE(asn1_type, buf)
+        assert res >= 0
+        assert buf[0] != self._ffi.NULL
+        buf = self._ffi.gc(
+            buf, lambda buffer: self._lib.OPENSSL_free(buffer[0])
+        )
+        return self._ffi.buffer(buf[0], res)[:]
+
+    def _parse_asn1_time(self, asn1_time):
+        assert asn1_time != self._ffi.NULL
+        generalized_time = self._lib.ASN1_TIME_to_generalizedtime(
+            asn1_time, self._ffi.NULL
+        )
+        assert generalized_time != self._ffi.NULL
+        generalized_time = self._ffi.gc(
+            generalized_time, self._lib.ASN1_GENERALIZEDTIME_free
+        )
+        time = self._asn1_string_to_ascii(
+            self._ffi.cast("ASN1_STRING *", generalized_time)
+        )
+        return datetime.datetime.strptime(time, "%Y%m%d%H%M%SZ")
+
 
 class GetCipherByName(object):
     def __init__(self, fmt):
diff --git a/src/cryptography/hazmat/backends/openssl/x509.py b/src/cryptography/hazmat/backends/openssl/x509.py
index e9af97f..70cec16 100644
--- a/src/cryptography/hazmat/backends/openssl/x509.py
+++ b/src/cryptography/hazmat/backends/openssl/x509.py
@@ -4,7 +4,6 @@
 
 from __future__ import absolute_import, division, print_function
 
-import datetime
 import ipaddress
 from email.utils import parseaddr
 
@@ -30,49 +29,12 @@
     return backend._ffi.buffer(buf, res)[:].decode()
 
 
-def _asn1_integer_to_int(backend, asn1_int):
-    bn = backend._lib.ASN1_INTEGER_to_BN(asn1_int, backend._ffi.NULL)
-    assert bn != backend._ffi.NULL
-    bn = backend._ffi.gc(bn, backend._lib.BN_free)
-    return backend._bn_to_int(bn)
-
-
-def _asn1_string_to_bytes(backend, asn1_string):
-    return backend._ffi.buffer(asn1_string.data, asn1_string.length)[:]
-
-
-def _asn1_string_to_ascii(backend, asn1_string):
-    return _asn1_string_to_bytes(backend, asn1_string).decode("ascii")
-
-
-def _asn1_string_to_utf8(backend, asn1_string):
-    buf = backend._ffi.new("unsigned char **")
-    res = backend._lib.ASN1_STRING_to_UTF8(buf, asn1_string)
-    assert res >= 0
-    assert buf[0] != backend._ffi.NULL
-    buf = backend._ffi.gc(
-        buf, lambda buffer: backend._lib.OPENSSL_free(buffer[0])
-    )
-    return backend._ffi.buffer(buf[0], res)[:].decode('utf8')
-
-
-def _asn1_to_der(backend, asn1_type):
-    buf = backend._ffi.new("unsigned char **")
-    res = backend._lib.i2d_ASN1_TYPE(asn1_type, buf)
-    assert res >= 0
-    assert buf[0] != backend._ffi.NULL
-    buf = backend._ffi.gc(
-        buf, lambda buffer: backend._lib.OPENSSL_free(buffer[0])
-    )
-    return backend._ffi.buffer(buf[0], res)[:]
-
-
 def _decode_x509_name_entry(backend, x509_name_entry):
     obj = backend._lib.X509_NAME_ENTRY_get_object(x509_name_entry)
     assert obj != backend._ffi.NULL
     data = backend._lib.X509_NAME_ENTRY_get_data(x509_name_entry)
     assert data != backend._ffi.NULL
-    value = _asn1_string_to_utf8(backend, data)
+    value = backend._asn1_string_to_utf8(data)
     oid = _obj2txt(backend, obj)
 
     return x509.NameAttribute(x509.ObjectIdentifier(oid), value)
@@ -101,7 +63,7 @@
 
 def _decode_general_name(backend, gn):
     if gn.type == backend._lib.GEN_DNS:
-        data = _asn1_string_to_bytes(backend, gn.d.dNSName)
+        data = backend._asn1_string_to_bytes(gn.d.dNSName)
         if data.startswith(b"*."):
             # This is a wildcard name. We need to remove the leading wildcard,
             # IDNA decode, then re-add the wildcard. Wildcard characters should
@@ -118,7 +80,7 @@
 
         return x509.DNSName(decoded)
     elif gn.type == backend._lib.GEN_URI:
-        data = _asn1_string_to_ascii(backend, gn.d.uniformResourceIdentifier)
+        data = backend._asn1_string_to_ascii(gn.d.uniformResourceIdentifier)
         parsed = urllib_parse.urlparse(data)
         hostname = idna.decode(parsed.hostname)
         if parsed.port:
@@ -142,7 +104,7 @@
         oid = _obj2txt(backend, gn.d.registeredID)
         return x509.RegisteredID(x509.ObjectIdentifier(oid))
     elif gn.type == backend._lib.GEN_IPADD:
-        data = _asn1_string_to_bytes(backend, gn.d.iPAddress)
+        data = backend._asn1_string_to_bytes(gn.d.iPAddress)
         data_len = len(data)
         if data_len == 8 or data_len == 32:
             # This is an IPv4 or IPv6 Network and not a single IP. This
@@ -173,7 +135,7 @@
             _decode_x509_name(backend, gn.d.directoryName)
         )
     elif gn.type == backend._lib.GEN_EMAIL:
-        data = _asn1_string_to_ascii(backend, gn.d.rfc822Name)
+        data = backend._asn1_string_to_ascii(gn.d.rfc822Name)
         name, address = parseaddr(data)
         parts = address.split(u"@")
         if name or not address:
@@ -192,7 +154,7 @@
             )
     elif gn.type == backend._lib.GEN_OTHERNAME:
         type_id = _obj2txt(backend, gn.d.otherName.type_id)
-        value = _asn1_to_der(backend, gn.d.otherName.value)
+        value = backend._asn1_to_der(gn.d.otherName.value)
         return x509.OtherName(x509.ObjectIdentifier(type_id), value)
     else:
         # x400Address or ediPartyName
@@ -294,7 +256,7 @@
     def serial(self):
         asn1_int = self._backend._lib.X509_get_serialNumber(self._x509)
         assert asn1_int != self._backend._ffi.NULL
-        return _asn1_integer_to_int(self._backend, asn1_int)
+        return self._backend._asn1_integer_to_int(asn1_int)
 
     def public_key(self):
         pkey = self._backend._lib.X509_get_pubkey(self._x509)
@@ -306,27 +268,12 @@
     @property
     def not_valid_before(self):
         asn1_time = self._backend._lib.X509_get_notBefore(self._x509)
-        return self._parse_asn1_time(asn1_time)
+        return self._backend._parse_asn1_time(asn1_time)
 
     @property
     def not_valid_after(self):
         asn1_time = self._backend._lib.X509_get_notAfter(self._x509)
-        return self._parse_asn1_time(asn1_time)
-
-    def _parse_asn1_time(self, asn1_time):
-        assert asn1_time != self._backend._ffi.NULL
-        generalized_time = self._backend._lib.ASN1_TIME_to_generalizedtime(
-            asn1_time, self._backend._ffi.NULL
-        )
-        assert generalized_time != self._backend._ffi.NULL
-        generalized_time = self._backend._ffi.gc(
-            generalized_time, self._backend._lib.ASN1_GENERALIZEDTIME_free
-        )
-        time = _asn1_string_to_ascii(
-            self._backend,
-            self._backend._ffi.cast("ASN1_STRING *", generalized_time)
-        )
-        return datetime.datetime.strptime(time, "%Y%m%d%H%M%SZ")
+        return self._backend._parse_asn1_time(asn1_time)
 
     @property
     def issuer(self):
@@ -410,12 +357,10 @@
     notice_reference = None
 
     if un.exptext != backend._ffi.NULL:
-        explicit_text = _asn1_string_to_utf8(backend, un.exptext)
+        explicit_text = backend._asn1_string_to_utf8(un.exptext)
 
     if un.noticeref != backend._ffi.NULL:
-        organization = _asn1_string_to_utf8(
-            backend, un.noticeref.organization
-        )
+        organization = backend._asn1_string_to_utf8(un.noticeref.organization)
 
         num = backend._lib.sk_ASN1_INTEGER_num(
             un.noticeref.noticenos
@@ -425,9 +370,7 @@
             asn1_int = backend._lib.sk_ASN1_INTEGER_value(
                 un.noticeref.noticenos, i
             )
-            notice_num = _asn1_integer_to_int(
-                backend, asn1_int
-            )
+            notice_num = backend._asn1_integer_to_int(asn1_int)
             notice_numbers.append(notice_num)
 
         notice_reference = x509.NoticeReference(
@@ -449,7 +392,7 @@
     if basic_constraints.pathlen == backend._ffi.NULL:
         path_length = None
     else:
-        path_length = _asn1_integer_to_int(backend, basic_constraints.pathlen)
+        path_length = backend._asn1_integer_to_int(basic_constraints.pathlen)
 
     return x509.BasicConstraints(ca, path_length)
 
@@ -482,8 +425,8 @@
         )
 
     if akid.serial != backend._ffi.NULL:
-        authority_cert_serial_number = _asn1_integer_to_int(
-            backend, akid.serial
+        authority_cert_serial_number = backend._asn1_integer_to_int(
+            akid.serial
         )
 
     return x509.AuthorityKeyIdentifier(
@@ -690,7 +633,7 @@
 def _decode_inhibit_any_policy(backend, asn1_int):
     asn1_int = backend._ffi.cast("ASN1_INTEGER *", asn1_int)
     asn1_int = backend._ffi.gc(asn1_int, backend._lib.ASN1_INTEGER_free)
-    skip_certs = _asn1_integer_to_int(backend, asn1_int)
+    skip_certs = backend._asn1_integer_to_int(asn1_int)
     return x509.InhibitAnyPolicy(skip_certs)