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venv/lib/python3.12/site-packages/asyncssh/crypto/dh.py

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+# Copyright (c) 2022 by Ron Frederick <ronf@timeheart.net> and others.
+#
+# This program and the accompanying materials are made available under
+# the terms of the Eclipse Public License v2.0 which accompanies this
+# distribution and is available at:
+#
+#     http://www.eclipse.org/legal/epl-2.0/
+#
+# This program may also be made available under the following secondary
+# licenses when the conditions for such availability set forth in the
+# Eclipse Public License v2.0 are satisfied:
+#
+#    GNU General Public License, Version 2.0, or any later versions of
+#    that license
+#
+# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
+#
+# Contributors:
+#     Ron Frederick - initial implementation, API, and documentation
+
+"""A shim around PyCA for Diffie Hellman key exchange"""
+
+from cryptography.hazmat.primitives.asymmetric import dh
+
+
+class DH:
+    """A shim around PyCA for Diffie Hellman key exchange"""
+
+    def __init__(self, g: int, p: int):
+        self._pn = dh.DHParameterNumbers(p, g)
+        self._priv_key = self._pn.parameters().generate_private_key()
+
+    def get_public(self) -> int:
+        """Return the public key to send in the handshake"""
+
+        pub_key = self._priv_key.public_key()
+
+        return pub_key.public_numbers().y
+
+    def get_shared(self, peer_public: int) -> int:
+        """Return the shared key from the peer's public key"""
+
+        peer_key = dh.DHPublicNumbers(peer_public, self._pn).public_key()
+        shared_key = self._priv_key.exchange(peer_key)
+
+        return int.from_bytes(shared_key, 'big')