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+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ * 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.
+ */
+
+/**
+ * @file parc_DiffieHellmanKeyShare.h
+ * @ingroup security
+ * @brief A Diffie Hellman key share.
+ *
+ */
+#ifndef libparc_parc_DiffieHellmanKeyShare_h
+#define libparc_parc_DiffieHellmanKeyShare_h
+
+#include <parc/security/parc_DiffieHellmanGroup.h>
+
+struct parc_diffie_hellman_keyshare;
+typedef struct parc_diffie_hellman_keyshare PARCDiffieHellmanKeyShare;
+
+/**
+ * Create a `PARCDiffieHellmanKeyShare` instance to hold one public and private
+ * Diffie Hellman key share for the specified group.
+ *
+ * @param [in] groupType A type of PARCDiffieHellmanGroup
+ *
+ * @return NULL Memory could not be allocated.
+ * @return non-NULL A pointer to a `PARCDiffieHellmanKeyShare` instance.
+ *
+ * Example:
+ * @code
+ * {
+ *     PARCDiffieHellmanKeyShare *keyShare = parcDiffieHellmanKeyShare_Create(PARCDiffieHellmanGroup_Secp521r1);
+ *
+ *     parcDiffieHellmanKeyShare_Release(&keyShare);
+ * }
+ * @endcode
+ */
+PARCDiffieHellmanKeyShare *parcDiffieHellmanKeyShare_Create(PARCDiffieHellmanGroup groupType);
+
+/**
+ * Increase the number of references to an instance of this object.
+ *
+ * Note that new instance is not created, only that the given instance's reference count
+ * is incremented. Discard the reference by invoking `parcDiffieHellman_Release()`.
+ *
+ * @param [in] keyShare A `PARCDiffieHellmanKeyShare` instance.
+ *
+ * @return The value of the input parameter @p instance.
+ *
+ * Example:
+ * @code
+ * {
+ *     ...
+ *
+ *     PARCDiffieHellmanKeyShare *keyShare = parcDiffieHellmanKeyShare_Acquire(keyShareInstance);
+ *
+ *     parcDiffieHellmanKeyShare_Release(&keyShare);
+ * }
+ * @endcode
+ *
+ * @see parcDiffieHellmanKeyShare_Release
+ */
+PARCDiffieHellmanKeyShare *parcDiffieHellmanKeyShare_Acquire(const PARCDiffieHellmanKeyShare *keyShare);
+
+/**
+ * Release a previously acquired reference to the specified instance,
+ * decrementing the reference count for the instance.
+ *
+ * The pointer to the instance is set to NULL as a side-effect of this function.
+ *
+ * If the invocation causes the last reference to the instance to be released,
+ * the instance is deallocated and the instance's implementation will perform
+ * additional cleanup and release other privately held references.
+ *
+ * @param [in,out] keyShareP A pointer to a pointer to the instance to release.
+ *
+ * Example:
+ * @code
+ * {
+ *     ...
+ *
+ *     PARCDiffieHellmanKeyShare *keyShare = parcDiffieHellmanKeyShare_Acquire(keyShareInstance);
+ *
+ *     parcDiffieHellmanKeyShare_Release(&keyShare);
+ * }
+ * @endcode
+ */
+void parcDiffieHellmanKeyShare_Release(PARCDiffieHellmanKeyShare **keyShareP);
+
+/**
+ * Serialize the public key part of a `PARCDiffieHellmanKeyShare.`
+ *
+ * The public key is saved to a `PARCBuffer` and can be used for transport if needed.
+ *
+ * @param [in] keyShare A `PARCDiffieHellmanKeyShare` instance.
+ *
+ * @return A `PARCBuffer` containing the public key of this key share.
+ *
+ * Example:
+ * @code
+ * {
+ *     PARCDiffieHellmanKeyShare *keyShare = parcDiffieHellmanKeyShare_Create(PARCDiffieHellmanGroup_Secp521r1);
+ *
+ *     PARCBuffer *publicKey = parcDiffieHellmanKeyShare_SerializePublicKey(keyShare);
+ *     // use the public key
+ *
+ *     parcBuffer_Release(&publicKey);
+ *     parcDiffieHellmanKeyShare_Release(&keyShare);
+ * }
+ * @endcode
+ */
+PARCBuffer *parcDiffieHellmanKeyShare_SerializePublicKey(PARCDiffieHellmanKeyShare *keyShare);
+
+/**
+ * Combine a `PARCDiffieHellmanKeyShare` with an encoded public key to create a shared secret.
+ *
+ * @param [in] keyShare A `PARCDiffieHellmanKeyShare` instance.
+ * @param [in] publicShare The public key share to use to derive the shared secrect.
+ *
+ * @return A `PARCBuffer` containing the shared secret from the Diffie Hellman exchange.
+ *
+ * Example:
+ * @code
+ * {
+ *     PARCDiffieHellmanKeyShare *keyShare = parcDiffieHellmanKeyShare_Create(PARCDiffieHellmanGroup_Secp521r1);
+ *
+ *     PARCBuffer *publicKey = parcDiffieHellmanKeyShare_SerializePublicKey(keyShare);
+ *
+ *     ...
+ *
+ *     PARCBuffer *sharedSecret = parcDiffieHellmanKeyShare_Combine(keyShare, publicKey);
+ *     // use the shared secret to derive other cryptographic secrets.
+ *
+ *     parcBuffer_Release(&sharedSecret);
+ *     parcBuffer_Release(&publicKey);
+ *     parcDiffieHellmanKeyShare_Release(&keyShare);
+ * }
+ * @endcode
+ */
+PARCBuffer *parcDiffieHellmanKeyShare_Combine(PARCDiffieHellmanKeyShare *keyShare, PARCBuffer *publicShare);
+#endif // libparc_parc_DiffieHellmanKeyShare_h