Split crypt into a package to allow alternative implementations (#189)
diff --git a/google/auth/crypt/base.py b/google/auth/crypt/base.py
new file mode 100644
index 0000000..05c5a2b
--- /dev/null
+++ b/google/auth/crypt/base.py
@@ -0,0 +1,64 @@
+# Copyright 2016 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Base classes for cryptographic signers and verifiers."""
+
+import abc
+
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Verifier(object):
+ """Abstract base class for crytographic signature verifiers."""
+
+ @abc.abstractmethod
+ def verify(self, message, signature):
+ """Verifies a message against a cryptographic signature.
+
+ Args:
+ message (Union[str, bytes]): The message to verify.
+ signature (Union[str, bytes]): The cryptography signature to check.
+
+ Returns:
+ bool: True if message was signed by the private key associated
+ with the public key that this object was constructed with.
+ """
+ # pylint: disable=missing-raises-doc,redundant-returns-doc
+ # (pylint doesn't recognize that this is abstract)
+ raise NotImplementedError('Verify must be implemented')
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Signer(object):
+ """Abstract base class for cryptographic signers."""
+
+ @abc.abstractproperty
+ def key_id(self):
+ """Optional[str]: The key ID used to identify this private key."""
+ raise NotImplementedError('Key id must be implemented')
+
+ @abc.abstractmethod
+ def sign(self, message):
+ """Signs a message.
+
+ Args:
+ message (Union[str, bytes]): The message to be signed.
+
+ Returns:
+ bytes: The signature of the message.
+ """
+ # pylint: disable=missing-raises-doc,redundant-returns-doc
+ # (pylint doesn't recognize that this is abstract)
+ raise NotImplementedError('Sign must be implemented')