add AuthorityKeyIdentifier from_issuer_public_key
Refactored SKI's creation code into a separate function, added
doctest examples
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index dfa91fa..a05be16 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -1160,6 +1160,28 @@
The serial number of the issuer's issuer.
+ .. classmethod:: from_issuer_public_key(public_key)
+
+ .. versionadded:: 1.0
+
+ Creates a new AuthorityKeyIdentifier instance using the public key
+ provided to generate the appropriate digest. This should be the
+ **issuer public key**. The resulting object will contain a
+ :attr:`~cryptography.x509.AuthorityKeyIdentifier.key_identifier`.
+ The generated digest is the SHA1 hash of the ``subjectPublicKey`` A
+ SN.1 bit string. This is the first recommendation in :rfc:`5280`
+ section 4.2.1.2.
+
+ :param certificate: The issuing :class:`~cryptography.x509.Certificate`.
+
+ .. doctest::
+
+ >>> from cryptography import x509
+ >>> from cryptography.hazmat.backends import default_backend
+ >>> cert = x509.load_pem_x509_certificate(pem_data, default_backend())
+ >>> x509.AuthorityKeyIdentifier.from_issuer_public_key(cert.public_key())
+ <AuthorityKeyIdentifier(key_identifier='X\x01\x84$\x1b\xbc+R\x94J=\xa5\x10r\x14Q\xf5\xaf:\xc9', authority_cert_issuer=None, authority_cert_serial_number=None)>
+
.. class:: SubjectKeyIdentifier
.. versionadded:: 0.9
@@ -1198,6 +1220,14 @@
, or
:class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`.
+ .. doctest::
+
+ >>> from cryptography import x509
+ >>> from cryptography.hazmat.backends import default_backend
+ >>> cert = x509.load_pem_x509_certificate(pem_data, default_backend())
+ >>> x509.SubjectKeyIdentifier.from_public_key(cert.public_key())
+ <SubjectKeyIdentifier(digest='X\x01\x84$\x1b\xbc+R\x94J=\xa5\x10r\x14Q\xf5\xaf:\xc9')>
+
.. class:: SubjectAlternativeName
.. versionadded:: 0.9