Add AEAD parameters and key types to C++ library.

PiperOrigin-RevId: 531532517

1 files changed, 53 insertions, 0 deletions

diff --git a/cc/aead/aead_key.h b/cc/aead/aead_key.h
new file mode 100644
index 000000000..64f7880b3
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+++ b/cc/aead/aead_key.h
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+// Copyright 2023 Google LLC
+//
+// 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.
+//
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef TINK_AEAD_AEAD_KEY_H_
+#define TINK_AEAD_AEAD_KEY_H_
+
+#include <string>
+
+#include "tink/aead/aead_parameters.h"
+#include "tink/key.h"
+
+namespace crypto {
+namespace tink {
+
+// Represents a function to encrypt and decrypt data using authenticated
+// encryption with associated data (AEAD).
+class AeadKey : public Key {
+ public:
+  // Returns the bytes prefixed to every ciphertext generated by this key.
+  //
+  // In order to make key rotation more efficient, Tink allows every AEAD key to
+  // have an associated ciphertext output prefix. When decrypting a ciphertext,
+  // only keys with a matching prefix have to be tried.
+  //
+  // Note that a priori, the output prefix may not be unique in a keyset
+  // (i.e., different keys in a keyset may have the same prefix or one prefix
+  // may be a prefix of another). To avoid this, built-in Tink keys use the
+  // convention that the prefix is either '0x00<big endian key id>' or
+  // '0x01<big endian key id>'.
+  virtual std::string GetOutputPrefix() const = 0;
+
+  const AeadParameters& GetParameters() const override = 0;
+
+  bool operator==(const Key& other) const override = 0;
+};
+
+}  // namespace tink
+}  // namespace crypto
+
+#endif  // TINK_AEAD_AEAD_KEY_H_