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diff --git a/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h b/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h
new file mode 100644
index 0000000000..682a8f7e7a
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+++ b/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h
@@ -0,0 +1,114 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * 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 GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_RECORD_PROTOCOL_CRYPTER_COMMON_H
+#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_RECORD_PROTOCOL_CRYPTER_COMMON_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/grpc.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+
+/**
+ * This file contains common implementation that will be used in both seal and
+ * unseal operations.
+ */
+
+/**
+ * Main struct for alts_record_protocol_crypter that will be used in both
+ * seal and unseal operations.
+ */
+typedef struct alts_record_protocol_crypter {
+  alts_crypter base;
+  gsec_aead_crypter* crypter;
+  alts_counter* ctr;
+} alts_record_protocol_crypter;
+
+/**
+ * This method performs input sanity checks on a subset of inputs to
+ * alts_crypter_process_in_place() for both seal and unseal operations.
+ *
+ * - rp_crypter: an alts_record_protocol_crypter instance.
+ * - data: it represents raw data that needs to be sealed in a seal operation or
+ *   protected data that needs to be unsealed in an unseal operation.
+ * - output_size: size of data written to the data buffer after a seal or
+ *   unseal operation.
+ * - error_details: a buffer containing an error message if any of checked
+ *   inputs is nullptr. It is legal to pass nullptr into error_details and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code input_sanity_check(
+    const alts_record_protocol_crypter* rp_crypter, const unsigned char* data,
+    size_t* output_size, char** error_details);
+
+/**
+ * This method increments the counter within an alts_record_protocol_crypter
+ * instance.
+ *
+ * - rp_crypter: an alts_record_protocol_crypter instance.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly or the counter is wrapped. It is legal to pass nullptr
+ *   into error_details and otherwise, the parameter should be freed with
+ *   gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code increment_counter(alts_record_protocol_crypter* rp_crypter,
+                                   char** error_details);
+
+/**
+ * This method creates an alts_crypter instance, and populates the fields
+ * that are common to both seal and unseal operations.
+ *
+ * - crypter: a gsec_aead_crypter instance used to perform AEAD decryption. The
+ *   function does not take ownership of crypter.
+ * - is_client: a flag indicating if the alts_crypter instance will be
+ *   used at the client (is_client = true) or server (is_client =
+ *   false) side.
+ * - overflow_size: overflow size of counter in bytes.
+ * - error_details: a buffer containing an error message if the method does
+ *   not function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success of creation, the method returns alts_record_protocol_crypter
+ * instance. Otherwise, it returns nullptr with its details specified in
+ * error_details (if error_details is not nullptr).
+ *
+ */
+alts_record_protocol_crypter* alts_crypter_create_common(
+    gsec_aead_crypter* crypter, bool is_client, size_t overflow_size,
+    char** error_details);
+
+/**
+ * For the following two methods, please refer to the corresponding API in
+ * alts_crypter.h for detailed specifications.
+ */
+size_t alts_record_protocol_crypter_num_overhead_bytes(const alts_crypter* c);
+
+void alts_record_protocol_crypter_destruct(alts_crypter* c);
+
+#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_RECORD_PROTOCOL_CRYPTER_COMMON_H \
+        */