add x448 private/public PEM/DER pkcs8/subjectpublickeyinfo vectors (#4667)

diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 9e26627..eb9ba4b 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -104,6 +104,13 @@
   encoded in several of the PKCS12 custom vectors.
 * ``asymmetric/EC/compressed_points.txt`` - Contains compressed public points
   generated using OpenSSL.
+* ``asymmetric/X448/x448-pkcs8-enc.pem`` and
+  ``asymmetric/X448/x448-pkcs8-enc.der`` contain an X448 key encrypted with
+  AES 256 CBC with the password ``password``.
+* ``asymmetric/X448/x448-pkcs8.pem`` and ``asymmetric/X448/x448-pkcs8.der``
+  contain an unencrypted X448 key.
+* ``asymmetric/X448/x448-pub.pem`` and ``asymmetric/X448/x448-pub.der`` contain
+  an X448 public key.
 
 
 Key exchange
diff --git a/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8-enc.der b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8-enc.der
new file mode 100644
index 0000000..d576f17
--- /dev/null
+++ b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8-enc.der
Binary files differ
diff --git a/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8-enc.pem b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8-enc.pem
new file mode 100644
index 0000000..6e72dc4
--- /dev/null
+++ b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8-enc.pem
@@ -0,0 +1,6 @@
+-----BEGIN ENCRYPTED PRIVATE KEY-----
+MIGrMFcGCSqGSIb3DQEFDTBKMCkGCSqGSIb3DQEFDDAcBAhfQQBzuXcjogICCAAw
+DAYIKoZIhvcNAgkFADAdBglghkgBZQMEASoEELhCu0RzKBjEmWe6F30A2cEEUI2y
+J54COuDdt/4p1lT4gTwPuFKkqrhRP5JvygIdxG/M8nMNCZS5j2wXwvFVg7MlXV0u
+r6ZCsUspfQmjqhagoHEMgWyee/b4gcJcRvg+y9HB
+-----END ENCRYPTED PRIVATE KEY-----
diff --git a/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8.der b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8.der
new file mode 100644
index 0000000..d8cecc2
--- /dev/null
+++ b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8.der
Binary files differ
diff --git a/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8.pem b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8.pem
new file mode 100644
index 0000000..1360397
--- /dev/null
+++ b/vectors/cryptography_vectors/asymmetric/X448/x448-pkcs8.pem
@@ -0,0 +1,4 @@
+-----BEGIN PRIVATE KEY-----
+MEYCAQAwBQYDK2VvBDoEONAHJqfHUJRF6ws+5Bf6Q1WX0oTyi2kbu9Lo85mLCAEi
+rLpN6PS/UUS+Tvm51RU5fNbrUjsPokqR
+-----END PRIVATE KEY-----
diff --git a/vectors/cryptography_vectors/asymmetric/X448/x448-pub.der b/vectors/cryptography_vectors/asymmetric/X448/x448-pub.der
new file mode 100644
index 0000000..b7313ca
--- /dev/null
+++ b/vectors/cryptography_vectors/asymmetric/X448/x448-pub.der
Binary files differ
diff --git a/vectors/cryptography_vectors/asymmetric/X448/x448-pub.pem b/vectors/cryptography_vectors/asymmetric/X448/x448-pub.pem
new file mode 100644
index 0000000..9ccea2f
--- /dev/null
+++ b/vectors/cryptography_vectors/asymmetric/X448/x448-pub.pem
@@ -0,0 +1,4 @@
+-----BEGIN PUBLIC KEY-----
+MEIwBQYDK2VvAzkA2NRMii6yWalecg8lVUFJpFYO5mpLIes32lYeGElbOCBVo5hu
+n/2vyTKP7oYJTa5i2f8gPguA0II=
+-----END PUBLIC KEY-----