diff --git a/quic/core/handshaker_delegate_interface.h b/quic/core/handshaker_delegate_interface.h
new file mode 100644
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+++ b/quic/core/handshaker_delegate_interface.h
@@ -0,0 +1,53 @@
+// Copyright (c) 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef QUICHE_QUIC_CORE_HANDSHAKER_DELEGATE_INTERFACE_H_
+#define QUICHE_QUIC_CORE_HANDSHAKER_DELEGATE_INTERFACE_H_
+
+#include "net/third_party/quiche/src/quic/core/quic_types.h"
+
+namespace quic {
+
+class QuicDecrypter;
+class QuicEncrypter;
+
+// Pure virtual class to get notified when particular handshake events occurred.
+class QUIC_EXPORT_PRIVATE HandshakerDelegateInterface {
+ public:
+  virtual ~HandshakerDelegateInterface() {}
+
+  // Called when new keys are available.
+  virtual void OnNewKeysAvailable(EncryptionLevel level,
+                                  std::unique_ptr<QuicDecrypter> decrypter,
+                                  bool set_alternative_decrypter,
+                                  bool latch_once_used,
+                                  std::unique_ptr<QuicEncrypter> encrypter) = 0;
+
+  // Called to set default encryption level to |level|.
+  virtual void SetDefaultEncryptionLevel(EncryptionLevel level) = 0;
+
+  // Called to discard old decryption keys to stop processing packets of
+  // encryption |level|.
+  virtual void DiscardOldDecryptionKey(EncryptionLevel level) = 0;
+
+  // Called to discard old encryption keys (and neuter obsolete data).
+  // TODO(fayang): consider to combine this with DiscardOldDecryptionKey.
+  virtual void DiscardOldEncryptionKey(EncryptionLevel level) = 0;
+
+  // Called to neuter ENCRYPTION_INITIAL data (without discarding initial keys).
+  virtual void NeuterUnencryptedData() = 0;
+
+  // Called to neuter data of HANDSHAKE_DATA packet number space. In QUIC
+  // crypto, this is called 1) when a client switches to forward secure
+  // encryption level and 2) a server successfully processes a forward secure
+  // packet. Temporarily use this method in TLS handshake when both endpoints
+  // switch to forward secure encryption level.
+  // TODO(fayang): use DiscardOldEncryptionKey instead of this method in TLS
+  // handshake when handshake key discarding settles down.
+  virtual void NeuterHandshakeData() = 0;
+};
+
+}  // namespace quic
+
+#endif  // QUICHE_QUIC_CORE_HANDSHAKER_DELEGATE_INTERFACE_H_