diff --git a/include/mbedcrypto/gcm.h b/include/mbedcrypto/gcm.h
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+/**
+ * \file gcm.h
+ *
+ * \brief This file contains GCM definitions and functions.
+ *
+ * The Galois/Counter Mode (GCM) for 128-bit block ciphers is defined
+ * in <em>D. McGrew, J. Viega, The Galois/Counter Mode of Operation
+ * (GCM), Natl. Inst. Stand. Technol.</em>
+ *
+ * For more information on GCM, see <em>NIST SP 800-38D: Recommendation for
+ * Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC</em>.
+ *
+ */
+/*
+ *  Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  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.
+ *
+ *  This file is part of Mbed Crypto (https://tls.mbed.org)
+ */
+
+#ifndef MBEDCRYPTO_GCM_H
+#define MBEDCRYPTO_GCM_H
+
+#include "cipher.h"
+
+#include <stdint.h>
+
+#define MBEDCRYPTO_GCM_ENCRYPT     1
+#define MBEDCRYPTO_GCM_DECRYPT     0
+
+#define MBEDCRYPTO_ERR_GCM_AUTH_FAILED                       -0x0012  /**< Authenticated decryption failed. */
+#define MBEDCRYPTO_ERR_GCM_HW_ACCEL_FAILED                   -0x0013  /**< GCM hardware accelerator failed. */
+#define MBEDCRYPTO_ERR_GCM_BAD_INPUT                         -0x0014  /**< Bad input parameters to function. */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if !defined(MBEDCRYPTO_GCM_ALT)
+
+/**
+ * \brief          The GCM context structure.
+ */
+typedef struct {
+    mbedcrypto_cipher_context_t cipher_ctx;  /*!< The cipher context used. */
+    uint64_t HL[16];                      /*!< Precalculated HTable low. */
+    uint64_t HH[16];                      /*!< Precalculated HTable high. */
+    uint64_t len;                         /*!< The total length of the encrypted data. */
+    uint64_t add_len;                     /*!< The total length of the additional data. */
+    unsigned char base_ectr[16];          /*!< The first ECTR for tag. */
+    unsigned char y[16];                  /*!< The Y working value. */
+    unsigned char buf[16];                /*!< The buf working value. */
+    int mode;                             /*!< The operation to perform:
+                                               #MBEDCRYPTO_GCM_ENCRYPT or
+                                               #MBEDCRYPTO_GCM_DECRYPT. */
+}
+mbedcrypto_gcm_context;
+
+#else  /* !MBEDCRYPTO_GCM_ALT */
+#include "gcm_alt.h"
+#endif /* !MBEDCRYPTO_GCM_ALT */
+
+/**
+ * \brief           This function initializes the specified GCM context,
+ *                  to make references valid, and prepares the context
+ *                  for mbedcrypto_gcm_setkey() or mbedcrypto_gcm_free().
+ *
+ *                  The function does not bind the GCM context to a particular
+ *                  cipher, nor set the key. For this purpose, use
+ *                  mbedcrypto_gcm_setkey().
+ *
+ * \param ctx       The GCM context to initialize.
+ */
+void mbedcrypto_gcm_init( mbedcrypto_gcm_context *ctx );
+
+/**
+ * \brief           This function associates a GCM context with a
+ *                  cipher algorithm and a key.
+ *
+ * \param ctx       The GCM context to initialize.
+ * \param cipher    The 128-bit block cipher to use.
+ * \param key       The encryption key.
+ * \param keybits   The key size in bits. Valid options are:
+ *                  <ul><li>128 bits</li>
+ *                  <li>192 bits</li>
+ *                  <li>256 bits</li></ul>
+ *
+ * \return          \c 0 on success.
+ * \return          A cipher-specific error code on failure.
+ */
+int mbedcrypto_gcm_setkey( mbedcrypto_gcm_context *ctx,
+                        mbedcrypto_cipher_id_t cipher,
+                        const unsigned char *key,
+                        unsigned int keybits );
+
+/**
+ * \brief           This function performs GCM encryption or decryption of a buffer.
+ *
+ * \note            For encryption, the output buffer can be the same as the
+ *                  input buffer. For decryption, the output buffer cannot be
+ *                  the same as input buffer. If the buffers overlap, the output
+ *                  buffer must trail at least 8 Bytes behind the input buffer.
+ *
+ * \param ctx       The GCM context to use for encryption or decryption.
+ * \param mode      The operation to perform: #MBEDCRYPTO_GCM_ENCRYPT or
+ *                  #MBEDCRYPTO_GCM_DECRYPT.
+ * \param length    The length of the input data. This must be a multiple of
+ *                  16 except in the last call before mbedcrypto_gcm_finish().
+ * \param iv        The initialization vector.
+ * \param iv_len    The length of the IV.
+ * \param add       The buffer holding the additional data.
+ * \param add_len   The length of the additional data.
+ * \param input     The buffer holding the input data.
+ * \param output    The buffer for holding the output data.
+ * \param tag_len   The length of the tag to generate.
+ * \param tag       The buffer for holding the tag.
+ *
+ * \return         \c 0 on success.
+ */
+int mbedcrypto_gcm_crypt_and_tag( mbedcrypto_gcm_context *ctx,
+                       int mode,
+                       size_t length,
+                       const unsigned char *iv,
+                       size_t iv_len,
+                       const unsigned char *add,
+                       size_t add_len,
+                       const unsigned char *input,
+                       unsigned char *output,
+                       size_t tag_len,
+                       unsigned char *tag );
+
+/**
+ * \brief           This function performs a GCM authenticated decryption of a
+ *                  buffer.
+ *
+ * \note            For decryption, the output buffer cannot be the same as
+ *                  input buffer. If the buffers overlap, the output buffer
+ *                  must trail at least 8 Bytes behind the input buffer.
+ *
+ * \param ctx       The GCM context.
+ * \param length    The length of the input data. This must be a multiple
+ *                  of 16 except in the last call before mbedcrypto_gcm_finish().
+ * \param iv        The initialization vector.
+ * \param iv_len    The length of the IV.
+ * \param add       The buffer holding the additional data.
+ * \param add_len   The length of the additional data.
+ * \param tag       The buffer holding the tag.
+ * \param tag_len   The length of the tag.
+ * \param input     The buffer holding the input data.
+ * \param output    The buffer for holding the output data.
+ *
+ * \return         0 if successful and authenticated.
+ * \return         #MBEDCRYPTO_ERR_GCM_AUTH_FAILED if the tag does not match.
+ */
+int mbedcrypto_gcm_auth_decrypt( mbedcrypto_gcm_context *ctx,
+                      size_t length,
+                      const unsigned char *iv,
+                      size_t iv_len,
+                      const unsigned char *add,
+                      size_t add_len,
+                      const unsigned char *tag,
+                      size_t tag_len,
+                      const unsigned char *input,
+                      unsigned char *output );
+
+/**
+ * \brief           This function starts a GCM encryption or decryption
+ *                  operation.
+ *
+ * \param ctx       The GCM context.
+ * \param mode      The operation to perform: #MBEDCRYPTO_GCM_ENCRYPT or
+ *                  #MBEDCRYPTO_GCM_DECRYPT.
+ * \param iv        The initialization vector.
+ * \param iv_len    The length of the IV.
+ * \param add       The buffer holding the additional data, or NULL
+ *                  if \p add_len is 0.
+ * \param add_len   The length of the additional data. If 0,
+ *                  \p add is NULL.
+ *
+ * \return          \c 0 on success.
+ */
+int mbedcrypto_gcm_starts( mbedcrypto_gcm_context *ctx,
+                int mode,
+                const unsigned char *iv,
+                size_t iv_len,
+                const unsigned char *add,
+                size_t add_len );
+
+/**
+ * \brief           This function feeds an input buffer into an ongoing GCM
+ *                  encryption or decryption operation.
+ *
+ *    `             The function expects input to be a multiple of 16
+ *                  Bytes. Only the last call before calling
+ *                  mbedcrypto_gcm_finish() can be less than 16 Bytes.
+ *
+ * \note            For decryption, the output buffer cannot be the same as
+ *                  input buffer. If the buffers overlap, the output buffer
+ *                  must trail at least 8 Bytes behind the input buffer.
+ *
+ * \param ctx       The GCM context.
+ * \param length    The length of the input data. This must be a multiple of
+ *                  16 except in the last call before mbedcrypto_gcm_finish().
+ * \param input     The buffer holding the input data.
+ * \param output    The buffer for holding the output data.
+ *
+ * \return         \c 0 on success.
+ * \return         #MBEDCRYPTO_ERR_GCM_BAD_INPUT on failure.
+ */
+int mbedcrypto_gcm_update( mbedcrypto_gcm_context *ctx,
+                size_t length,
+                const unsigned char *input,
+                unsigned char *output );
+
+/**
+ * \brief           This function finishes the GCM operation and generates
+ *                  the authentication tag.
+ *
+ *                  It wraps up the GCM stream, and generates the
+ *                  tag. The tag can have a maximum length of 16 Bytes.
+ *
+ * \param ctx       The GCM context.
+ * \param tag       The buffer for holding the tag.
+ * \param tag_len   The length of the tag to generate. Must be at least four.
+ *
+ * \return          \c 0 on success.
+ * \return          #MBEDCRYPTO_ERR_GCM_BAD_INPUT on failure.
+ */
+int mbedcrypto_gcm_finish( mbedcrypto_gcm_context *ctx,
+                unsigned char *tag,
+                size_t tag_len );
+
+/**
+ * \brief           This function clears a GCM context and the underlying
+ *                  cipher sub-context.
+ *
+ * \param ctx       The GCM context to clear.
+ */
+void mbedcrypto_gcm_free( mbedcrypto_gcm_context *ctx );
+
+/**
+ * \brief          The GCM checkup routine.
+ *
+ * \return         \c 0 on success.
+ * \return         \c 1 on failure.
+ */
+int mbedcrypto_gcm_self_test( int verbose );
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* gcm.h */