mbedtls/include/psa/crypto_driver.h

/**
 * \file psa/crypto_driver.h
 * \brief Platform Security Architecture cryptographic driver module
 * 
 * This file describes an API for driver developers to implement to enable
 * hardware to be called in a standardized way by a PSA Cryptographic API
 * implementation. The API described is not intended to be called by
 * application developers.
 */

/*
 *  Copyright (C) 2018, ARM Limited, 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.
 */
#ifndef __PSA_CRYPTO_DRIVER_H__
#define __PSA_CRYPTO_DRIVER_H__

#include <stddef.h>
#include <stdint.h>

/** The following types are redefinitions from the psa/crypto.h file.
 * It is intended that these will be moved to a new common header file to 
 * avoid duplication. They are included here for expediency in publication.
 */
typedef uint32_t psa_status_t;
typedef uint32_t psa_algorithm_t;
typedef uint8_t encrypt_or_decrypt_t;
typedef uint32_t psa_key_slot_t;
typedef uint32_t psa_key_type_t;
typedef uint32_t psa_key_usage_t;

/** \defgroup opaque_mac Opaque Message Authentication Code
 * Generation and authentication of Message Authentication Codes (MACs) using
 * opaque keys can be done either as a single function call (via the 
 * `pcd_mac_opaque_generate_t` or `psa_mac_opaque_verify_t` functions), or in
 * parts using the following sequence:
 * - `psa_mac_opaque_setup_t`
 * - `psa_mac_opaque_update_t`
 * - `psa_mac_opaque_update_t`
 * - ...
 * - `psa_mac_opaque_finish_t` or `psa_mac_opaque_finish_verify_t`
 * 
 * If a previously started Opaque MAC operation needs to be terminated, it 
 * should be done so by the `psa_mac_opaque_abort_t`. Failure to do so may
 * result in allocated resources not being freed or in other undefined
 * behavior.
 */
/**@{*/
/** \brief A function that starts a MAC operation for a PSA Crypto Driver 
 * implementation using an opaque key
 * 
 * \param[in,out] p_context     A structure that will contain the 
 *                              hardware-specific MAC context
 * \param[in] key_slot          The slot of the key to be used for the
 *                              operation
 * \param[in] algorithm         The algorithm to be used to underly the MAC 
 *                              operation
 * 
 * \retval  PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_opaque_setup_t)(void *p_context,
                                               psa_key_slot_t key_slot,
                                               psa_algorithm_t algorithm);

/** \brief A function that continues a previously started MAC operation using
 * an opaque key
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously-established MAC operation to be
 *                              continued
 * \param[in] p_input           A buffer containing the message to be appended
 *                              to the MAC operation
 * \param[in] input_length  The size in bytes of the input message buffer
 */
typedef psa_status_t (*pcd_mac_opaque_update_t)(void *p_context,
                                                const uint8_t *p_input,
                                                size_t input_length);

/** \brief a function that completes a previously started MAC operation by
 * returning the resulting MAC using an opaque key
 * 
 * \param[in,out] p_context     A hardware-specific structure for the 
 *                              previously started MAC operation to be 
 *                              finished
 * \param[out] p_mac            A buffer where the generated MAC will be
 *                              placed
 * \param[in] mac_size          The size in bytes of the buffer that has been
 *                              allocated for the `output` buffer
 * \param[out] p_mac_length     After completion, will contain the number of
 *                              bytes placed in the `p_mac` buffer
 * 
 * \retval PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_opaque_finish_t)(void *p_context,
                                                uint8_t *p_mac,
                                                size_t mac_size,
                                                size_t *p_mac_length);

/** \brief A function that completes a previously started MAC operation by
 * comparing the resulting MAC against a known value using an opaque key
 * 
 * \param[in,out] p_context A hardware-specific structure for the previously
 *                          started MAC operation to be fiinished
 * \param[in] p_mac         The MAC value against which the resulting MAC will
 *                          be compared against
 * \param[in] mac_length    The size in bytes of the value stored in `p_mac`
 * 
 * \retval PSA_SUCCESS
 *         The operation completed successfully and the MACs matched each
 *         other
 * \retval PSA_ERROR_INVALID_SIGNATURE
 *         The operation completed successfully, but the calculated MAC did
 *         not match the provided MAC
 */
typedef psa_status_t (*pcd_mac_opaque_finish_verify_t)(void *p_context,
                                                       const uint8_t *p_mac,
                                                       size_t mac_length);

/** \brief A function that aborts a previous started opaque-key MAC operation

 * \param[in,out] p_context A hardware-specific structure for the previously
 *                          started MAC operation to be aborted
 */
typedef psa_status_t (*pcd_mac_opaque_abort_t)(void *p_context);

/** \brief A function that performs a MAC operation in one command and returns
 * the calculated MAC using an opaque key
 * 
 * \param[in] p_input           A buffer containing the message to be MACed
 * \param[in] input_length      The size in bytes of `p_input`
 * \param[in] key_slot          The slot of the key to be used
 * \param[in] alg               The algorithm to be used to underlie the MAC
 *                              operation
 * \param[out] p_mac            A buffer where the generated MAC will be
 *                              placed
 * \param[in] mac_size          The size in bytes of the `p_mac` buffer
 * \param[out] p_mac_length     After completion, will contain the number of
 *                              bytes placed in the `output` buffer
 * 
 * \retval PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*pcd_mac_opaque_generate_t)(const uint8_t *p_input,
                                                  size_t input_length,
                                                  psa_key_slot_t key_slot,
                                                  psa_algorithm_t alg,
                                                  uint8_t *p_mac,
                                                  size_t mac_size,
                                                  size_t *p_mac_length);

/** \brief A function that performs an MAC operation in one command and
 * compare the resulting MAC against a known value using an opaque key
 * 
 * \param[in] p_input       A buffer containing the message to be MACed
 * \param[in] input_length  The size in bytes of `input`
 * \param[in] key_slot      The slot of the key to be used
 * \param[in] alg           The algorithm to be used to underlie the MAC
 *                          operation
 * \param[in] p_mac         The MAC value against which the resulting MAC will
 *                          be compared against
 * \param[in] mac_length   The size in bytes of `mac`
 * 
 * \retval PSA_SUCCESS
 *         The operation completed successfully and the MACs matched each
 *         other
 * \retval PSA_ERROR_INVALID_SIGNATURE
 *         The operation completed successfully, but the calculated MAC did
 *         not match the provided MAC
 */
typedef psa_status_t (*pcd_mac_opaque_verify_t)(const uint8_t *p_input,
                                                size_t input_length,
                                                psa_key_slot_t key_slot,
                                                psa_algorithm_t alg,
                                                const uint8_t *p_mac,
                                                size_t mac_length);

/** \brief A struct containing all of the function pointers needed to
 * implement MAC operations using opaque keys.
 * 
 * PSA Crypto API implementations should populate the table as appropriate
 * upon startup.
 *
 * If one of the functions is not implemented (such as
 * `pcd_mac_opaque_generate_t`), it should be set to NULL.
 * 
 * Driver implementers should ensure that they implement all of the functions
 * that make sense for their hardware, and that they provide a full solution
 * (for example, if they support `p_setup`, they should also support
 * `p_update` and at least one of `p_finish` or `p_finish_verify`).
 * 
 */
struct pcd_mac_opaque_t {
    /**The size in bytes of the hardware-specific Opaque-MAC Context structure
    */
    size_t                          context_size;
    /** Function that performs the setup operation
     */
    pcd_mac_opaque_setup_t          *p_setup;
    /** Function that performs the update operation
     */
    pcd_mac_opaque_update_t         *p_update;
    /** Function that completes the operation
     */
    pcd_mac_opaque_finish_t         *p_finish;
    /** Function that completed a MAC operation with a verify check
     */
    pcd_mac_opaque_finish_verify_t  *p_finish_verify;
    /** Function that aborts a previoustly started operation
     */
    pcd_mac_opaque_abort_t          *p_abort;
    /** Function that performs the MAC operation in one call
     */
    pcd_mac_opaque_generate_t       *p_mac;
    /** Function that performs the MAC and verify operation in one call
     */
    pcd_mac_opaque_verify_t         *p_mac_verify;
};
/**@}*/

/** \defgroup transparent_mac Transparent Message Authentication Code
 * Generation and authentication of Message Authentication Codes (MACs) using
 * transparent keys can be done either as a single function call (via the 
 * `pcd_mac_transparent_generate_t` or `psa_mac_transparent_verify_t`
 * functions), or in parts using the following sequence:
 * - `psa_mac_transparent_setup_t`
 * - `psa_mac_transparent_update_t`
 * - `psa_mac_transparent_update_t`
 * - ...
 * - `psa_mac_transparent_finish_t` or `psa_mac_transparent_finish_verify_t`
 * 
 * If a previously started Transparent MAC operation needs to be terminated, it 
 * should be done so by the `psa_mac_transparent_abort_t`. Failure to do so may
 * result in allocated resources not being freed or in other undefined
 * behavior.
 * 
 */
/**@{*/

/** \brief The hardware-specific transparent-key MAC context structure
 *
 * The contents of this structure are implementation dependent and are
 * therefore not described here.
 */
typedef struct pcd_mac_transparent_context_s pcd_mac_transparent_context_t;

/** \brief The function prototype for the setup operation of a
 * transparent-key MAC operation
 * 
 *  Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>_setup
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying primitive, and `MAC_VARIANT`
 * is the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in,out] p_context     A structure that will contain the 
 *                              hardware-specific MAC context
 * \param[in] p_key             A buffer containing the cleartext key material
 *                              to be used in the operation
 * \param[in] key_length        The size in bytes of the key material
 * 
 * \retval  PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_transparent_setup_t)(pcd_mac_transparent_context_t *p_context,
                                                    const uint8_t *p_key,
                                                    size_t key_length);

/** \brief The function prototype for the update operation of a
 * transparent-key MAC operation
 *
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>_update
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm, and `MAC_VARIANT`
 * is the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously-established MAC operation to be
 *                              continued
 * \param[in] p_input           A buffer containing the message to be appended
 *                              to the MAC operation
 * \param[in] input_length      The size in bytes of the input message buffer
 */
typedef psa_status_t (*pcd_mac_transparent_update_t)(pcd_mac_transparent_context_t *p_context,
                                                     const uint8_t *p_input,
                                                     size_t input_length);

/** \brief  The function prototype for the finish operation of a
 * transparent-key MAC operation
 * 
 * Functions that implement the prototype should be named in the following
 *  convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>_finish
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm, and `MAC_VARIANT` is
 * the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started MAC operation to be
 *                              finished
 * \param[out] p_mac            A buffer where the generated MAC will be placed
 * \param[in] mac_length        The size in bytes of the buffer that has been
 *                              allocated for the `p_mac` buffer
 * 
 * \retval PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_transparent_finish_t)(pcd_mac_transparent_context_t *p_context,
                                                     uint8_t *p_mac,
                                                     size_t mac_length);

/** \brief The function prototype for the finish and verify operation of a
 * transparent-key MAC operation
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>_finish_verify
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm, and `MAC_VARIANT` is
 * the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started MAC operation to be
 *                              verified and finished
 * \param[in] p_mac             A buffer containing the MAC that will be used
 *                              for verification
 * \param[in] mac_length        The size in bytes of the data in the `p_mac`
 *                              buffer
 * 
 * \retval PSA_SUCCESS
 *          The operation completed successfully and the comparison matched
 */
typedef psa_status_t (*pcd_mac_transparent_finish_verify_t)(pcd_mac_transparent_context_t *p_context,
                                                            const uint8_t *p_mac,
                                                            size_t mac_length);

/** \brief The function prototype for the abort operation for a previously
 * started transparent-key MAC operation
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>_abort
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm, and `MAC_VARIANT` is
 * the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started MAC operation to be
 *                              aborted
 * 
 */
typedef psa_status_t (*pcd_mac_transparent_abort_t)(pcd_mac_transparent_context_t *p_context);

/** \brief The function prototype for a one-shot operation of a transparent-key
 * MAC operation
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm, and `MAC_VARIANT` is 
 * the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in] p_input        A buffer containing the data to be MACed
 * \param[in] input_length   The length in bytes of the `p_input` data
 * \param[in] p_key          A buffer containing the key material to be used
 *                           for the MAC operation
 * \param[in] key_length     The length in bytes of the `p_key` data
 * \param[in] alg            The algorithm to be performed
 * \param[out] p_mac         The buffer where the resulting MAC will be placed
 *                           upon success
 * \param[in] mac_length     The length in bytes of the `p_mac` buffer
 */
typedef psa_status_t (*pcd_mac_transparent_t)(const uint8_t *p_input,
                                              size_t input_length,
                                              const uint8_t *p_key,
                                              size_t key_length,
                                              psa_algorithm_t alg,
                                              uint8_t *p_mac,
                                              size_t mac_length);

/** \brief The function prototype for a one-shot operation of a transparent-key
 * MAC Verify operation
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_mac_transparent_<ALGO>_<MAC_VARIANT>_verify
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm, and `MAC_VARIANT` is
 * the specific variant of a MAC operation (such as HMAC or CMAC)
 * 
 * \param[in] p_input        A buffer containing the data to be MACed
 * \param[in] input_length   The length in bytes of the `p_input` data
 * \param[in] p_key          A buffer containing the key material to be used
 *                           for the MAC operation
 * \param[in] key_length     The length in bytes of the `p_key` data
 * \param[in] alg            The algorithm to be performed
 * \param[in] p_mac          The MAC data to be compared
 * \param[in] mac_length     The length in bytes of the `p_mac` buffer
 * 
 * \retval PSA_SUCCESS
 *  The operation completed successfully and the comparison matched
 */
typedef psa_status_t (*pcd_mac_transparent_verify_t)(const uint8_t *p_input,
                                                     size_t input_length,
                                                     const uint8_t *p_key,
                                                     size_t key_length,
                                                     psa_algorithm_t alg,
                                                     const uint8_t *p_mac,
                                                     size_t mac_length);
/**@}*/

/** \defgroup opaque_cipher Opaque Symmetric Ciphers
 * 
 * Encryption and Decryption using opaque keys in block modes other than ECB
 * must be done in multiple parts, using the following flow:
 * - `pcd_cipher_opaque_setup_t`
 * - `pcd_cipher_opaque_set_iv_t` (optional depending upon block mode)
 * - `pcd_cipher_opaque_update_t`
 * - ...
 * - `pcd_cipher_opaque_finish_t`

 * If a previously started Opaque Cipher operation needs to be terminated, it 
 * should be done so by the `psa_cipher_opaque_abort_t`. Failure to do so may
 * result in allocated resources not being freed or in other undefined
 * behavior.
 * 
 * In situations where a PSA Cryptographic API implementation is using a block
 * mode not-supported by the underlying hardware or driver, it can construct
 * the block mode itself, while calling the `pcd_cipher_opaque_ecb_t` function
 * pointer for the cipher operations.
 */
/**@{*/

/** \brief A function pointer that provides the cipher setup function for
 * opaque-key operations
 *
 * \param[in,out] p_context     A structure that will contain the
 *                              hardware-specific cipher context.
 * \param[in] key_slot          The slot of the key to be used for the
 *                              operation
 * \param[in] algorithm         The algorithm to be used in the cipher
 *                              operation
 * \param[in] direction         Indicates whether the operation is an encrypt
 *                              or decrypt
 * 
 * \retval PSA_SUCCESS
 * \retval PSA_ERROR_NOT_SUPPORTED
 */
typedef psa_status_t (*pcd_cipher_opaque_setup_t)(void *p_context,
                                                  psa_key_slot_t key_slot,
                                                  psa_algorithm_t algorithm,
                                                  encrypt_or_decrypt_t direction);

/** \brief A function pointer that sets the initialization vector (if
 * necessary) for an opaque cipher operation
 * 
 * Rationale: The `psa_cipher_*` function in the PSA Cryptographic API has two
 * IV functions: one to set the IV, and one to generate it internally. The
 * generate function is not necessary for the driver API as the PSA Crypto
 * implementation can do the generation using its RNG features.
 * 
 * \param[in,out] p_context     A structure that contains the previously set up
 *                              hardware-specific cipher context
 * \param[in] p_iv              A buffer containing the initialization vector
 * \param[in] iv_length         The size (in bytes) of the `p_iv` buffer
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_opaque_set_iv_t)(void *p_context,
                                                   const uint8_t *p_iv,
                                                   size_t iv_length);

/** \brief A function that continues a previously started opaque-key cipher
 * operation
 * 
 * \param[in,out] p_context         A hardware-specific structure for the
 *                                  previously started cipher operation
 * \param[in] p_input               A buffer containing the data to be
 *                                  encrypted/decrypted
 * \param[in] input_size            The size in bytes of the buffer pointed to
 *                                  by `p_input`
 * \param[out] p_output             The caller-allocated buffer where the
 *                                  output will be placed
 * \param[in] output_size           The allocated size in bytes of the
 *                                  `p_output` buffer
 * \param[out] p_output_length      After completion, will contain the number
 *                                  of bytes placed in the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_opaque_update_t)(void *p_context,
                                                   const uint8_t *p_input,
                                                   size_t input_size,
                                                   uint8_t *p_output,
                                                   size_t output_size,
                                                   size_t *p_output_length);

/** \brief A function that completes a previously started opaque-key cipher
 * operation
 *
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started cipher operation
 * \param[out] p_output         The caller-allocated buffer where the output
 *                              will be placed
 * \param[in] output_size       The allocated size in bytes of the `p_output`
 *                              buffer
 * \param[out] p_output_length  After completion, will contain the number of
 *                              bytes placed in the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_opaque_finish_t)(void *p_context,
                                                   uint8_t *p_output,
                                                   size_t output_size,
                                                   size_t *p_output_length);

/** \brief A function that aborts a previously started opaque-key cipher
 * operation
 *
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started cipher operation
 */
typedef psa_status_t (*pcd_cipher_opaque_abort_t)(void *p_context);

/** \brief A function that performs the ECB block mode for opaque-key cipher
 * operations
 * 
 * Note: this function should only be used with implementations that do not
 * provide a needed higher-level operation.
 * 
 * \param[in] key_slot      The slot of the key to be used for the operation
 * \param[in] algorithm     The algorithm to be used in the cipher operation
 * \param[in] direction     Indicates whether the operation is an encrypt or
 *                          decrypt
 * \param[in] p_input       A buffer containing the data to be
 *                          encrypted/decrypted
 * \param[in] input_size    The size in bytes of the buffer pointed to by
 *                          `p_input`
 * \param[out] p_output     The caller-allocated buffer where the output will
 *                          be placed
 * \param[in] output_size   The allocated size in bytes of the `p_output`
 *                          buffer
 * 
 * \retval PSA_SUCCESS
 * \retval PSA_ERROR_NOT_SUPPORTED
 */
typedef psa_status_t (*pcd_cipher_opaque_ecb_t)(psa_key_slot_t key_slot,
                                                psa_algorithm_t algorithm,
                                                encrypt_or_decrypt_t direction,
                                                const uint8_t *p_input,
                                                size_t input_size,
                                                uint8_t *p_output,
                                                size_t output_size);

/**
 * \brief A struct containing all of the function pointers needed to implement
 * cipher operations using opaque keys.
 * 
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup.
 * 
 * If one of the functions is not implemented (such as
 * `pcd_cipher_opaque_ecb_t`), it should be set to NULL.
 */
struct pcd_cipher_opaque_t {
    /** The size in bytes of the hardware-specific Opaque Cipher context
     * structure
     */
    size_t                      size;
    /** Function that performs the setup operation */
    pcd_cipher_opaque_setup_t  *p_setup;
    /** Function that sets the IV (if necessary) */
    pcd_cipher_opaque_set_iv_t *p_set_iv;
    /** Function that performs the update operation */
    pcd_cipher_opaque_update_t *p_update;
    /** Function that completes the operation */
    pcd_cipher_opaque_finish_t *p_finish;
    /** Function that aborts the operation */
    pcd_cipher_opaque_abort_t  *p_abort;
    /** Function that performs ECB mode for the cipher
     * (Danger: ECB mode should not be used directly by clients of the PSA
     * Crypto Client API)
     */
    pcd_cipher_opaque_ecb_t    *p_ecb;
};

/**@}*/

/** \defgroup transparent_cipher Transparent Block Cipher
 * Encryption and Decryption using transparent keys in block modes other than
 * ECB must be done in multiple parts, using the following flow:
 * - `pcd_cipher_transparent_setup_t`
 * - `pcd_cipher_transparent_set_iv_t` (optional depending upon block mode)
 * - `pcd_cipher_transparent_update_t`
 * - ...
 * - `pcd_cipher_transparent_finish_t`

 * If a previously started Transparent Cipher operation needs to be terminated,
 * it should be done so by the `psa_cipher_transparent_abort_t`. Failure to do
 * so may result in allocated resources not being freed or in other undefined
 * behavior.
 */
/**@{*/

/** \brief The hardware-specific transparent-key Cipher context structure
 * 
 * The contents of this structure are implementation dependent and are
 * therefore not described here.
 */
typedef struct pcd_cipher_transparent_context_s pcd_cipher_transparent_context_t;

/** \brief The function prototype for the setup operation of transparent-key
 * block cipher operations.
 *  Functions that implement the prototype should be named in the following
 * conventions:
 * ~~~~~~~~~~~~~{.c}
 * pcd_cipher_transparent_setup_<CIPHER_NAME>_<MODE>
 * ~~~~~~~~~~~~~
 * Where
 * - `CIPHER_NAME` is the name of the underlying block cipher (i.e. AES or DES)
 * - `MODE` is the block mode of the cipher operation (i.e. CBC or CTR)
 * or for stream ciphers:
 * ~~~~~~~~~~~~~{.c}
 * pcd_cipher_transparent_setup_<CIPHER_NAME>
 * ~~~~~~~~~~~~~
 * Where `CIPHER_NAME` is the name of a stream cipher (i.e. RC4)
 * 
 * \param[in,out] p_context     A structure that will contain the
 *                              hardware-specific cipher context
 * \param[in] direction         Indicates if the operation is an encrypt or a
 *                              decrypt
 * \param[in] p_key_data        A buffer containing the cleartext key material
 *                              to be used in the operation
 * \param[in] key_data_size     The size in bytes of the key material
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_transparent_setup_t)(pcd_cipher_transparent_context_t *p_context,
                                                       encrypt_or_decrypt_t direction,
                                                       const uint8_t *p_key_data,
                                                       size_t key_data_size);

/** \brief The function prototype for the set initialization vector operation
 * of transparent-key block cipher operations
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_cipher_transparent_set_iv_<CIPHER_NAME>_<MODE>
 * ~~~~~~~~~~~~~
 * Where
 * - `CIPHER_NAME` is the name of the underlying block cipher (i.e. AES or DES)
 * - `MODE` is the block mode of the cipher operation (i.e. CBC or CTR)
 * 
 * \param[in,out] p_context     A structure that contains the previously setup
 *                              hardware-specific cipher context
 * \param[in] p_iv              A buffer containing the initialization vecotr
 * \param[in] iv_length         The size in bytes of the contents of `p_iv`
 * 
 * \retval PSA_SUCCESS
*/
typedef psa_status_t (*pcd_cipher_transparent_set_iv_t)(pcd_cipher_transparent_context_t *p_context,
                                                        const uint8_t *p_iv,
                                                        size_t iv_length);

/** \brief The function prototype for the update operation of transparent-key
 * block cipher operations.
 *
 *  Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_cipher_transparent_update_<CIPHER_NAME>_<MODE>
 * ~~~~~~~~~~~~~
 * Where
 * - `CIPHER_NAME` is the name of the underlying block cipher (i.e. AES or DES)
 * - `MODE` is the block mode of the cipher operation (i.e. CBC or CTR)
 * 
 * \param[in,out] p_context         A hardware-specific structure for the
 *                                  previously started cipher operation
 * \param[in] p_input               A buffer containing the data to be
 *                                  encrypted or decrypted
 * \param[in] input_size            The size in bytes of the `p_input` buffer
 * \param[out] p_output             A caller-allocated buffer where the
 *                                  generated output will be placed
 * \param[in] output_size           The size in bytes of the `p_output` buffer
 * \param[out] p_output_length      After completion, will contain the number
 *                                  of bytes placed in the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_transparent_update_t)(pcd_cipher_transparent_context_t *p_context,
                                                        const uint8_t *p_input,
                                                        size_t input_size,
                                                        uint8_t *p_output,
                                                        size_t output_size,
                                                        size_t *p_output_length);

/** \brief The function prototype for the finish operation of transparent-key
 * block cipher operations.
*
 *  Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_cipher_transparent_finish_<CIPHER_NAME>_<MODE>
 * ~~~~~~~~~~~~~
 * Where
 * - `CIPHER_NAME` is the name of the underlying block cipher (i.e. AES or DES)
 * - `MODE` is the block mode of the cipher operation (i.e. CBC or CTR)
 *
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started cipher operation
 * \param[out] p_output         A caller-allocated buffer where the generated
 *                              output will be placed
 * \param[in] output_size       The size in bytes of the `p_output` buffer
 * \param[out] p_output_length  After completion, will contain the number of
 *                              bytes placed in the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_transparent_finish_t)(pcd_cipher_transparent_context_t *p_context,
                                                        uint8_t *p_output,
                                                        size_t output_size,
                                                        size_t *p_output_length);

/** \brief The function prototype for the abort operation of transparent-key
 * block cipher operations.
 * 
 *  Functions that implement the following prototype should be named in the
 * following convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_cipher_transparent_abort_<CIPHER_NAME>_<MODE>
 * ~~~~~~~~~~~~~
 * Where
 * - `CIPHER_NAME` is the name of the underlying block cipher (i.e. AES or DES)
 * - `MODE` is the block mode of the cipher operation (i.e. CBC or CTR)
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started cipher operation
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_transparent_abort_t)(pcd_cipher_transparent_context_t *p_context);

/**@}*/

/** \defgroup driver_digest Message Digests
 * 
 * Generation and authentication of Message Digests (aka hashes) must be done
 * in parts using the following sequence:
 * - `psa_hash_setup_t`
 * - `psa_hash_update_t`
 * - ...
 * - `psa_hash_finish_t`
 * 
 * If a previously started Message Digest operation needs to be terminated
 * before the `psa_hash_finish_t` operation is complete, it should be aborted
 * by the `psa_hash_abort_t`. Failure to do so may result in allocated
 * resources not being freed or in other undefined behavior.
 */
/**@{*/

/** \brief The hardware-specific hash context structure
 * 
 * The contents of this structure are implementation dependent and are
 * therefore not described here
 */
typedef struct pcd_hash_context_s pcd_hash_context_t;

/** \brief The function prototype for the start operation of a hash (message
 * digest) operation
 * 
 *  Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_hash_<ALGO>_setup
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying hash function
 * 
 * \param[in,out] p_context     A structure that will contain the
 * hardware-specific hash context
 * 
 * \retval  PSA_SUCCESS     Success.
 */
typedef psa_status_t (*pcd_hash_setup_t)(pcd_hash_context_t *p_context);

/** \brief The function prototype for the update operation of a hash (message
 * digest) operation
 *
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_hash_<ALGO>_update
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously-established hash operation to be
 *                              continued
 * \param[in] p_input           A buffer containing the message to be appended
 *                              to the hash operation
 * \param[in] input_length      The size in bytes of the input message buffer
 */
typedef psa_status_t (*pcd_hash_update_t)(pcd_hash_context_t *p_context,
                                          const uint8_t *p_input,
                                          size_t input_length);

/** \brief  The prototype for the finish operation of a hash (message digest)
 * operation
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_hash_<ALGO>_finish
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm
 * 
 * \param[in,out] p_context     A hardware-specific structure for the
 *                              previously started hash operation to be
 *                              fiinished
 * \param[out] p_output         A buffer where the generated digest will be
 *                              placed
 * \param[in] output_size       The size in bytes of the buffer that has been
 *                              allocated for the `p_output` buffer
 * \param[out] p_output_length  The number of bytes placed in `p_output` after
 *                              success
 * 
 * \retval PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_hash_finish_t)(pcd_hash_context_t *p_context,
                                          uint8_t *p_output,
                                          size_t output_size,
                                          size_t *p_output_length);

/** \brief The function prototype for the abort operation of a hash (message
 * digest) operation
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_hash_<ALGO>_abort
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying algorithm
 * 
 * \param[in,out] p_context A hardware-specific structure for the previously
 *                          started hash operation to be aborted
 */
typedef void (*pcd_hash_abort_t)(pcd_hash_context_t *p_context);

/**@}*/


/** \defgroup opaque_asymmetric Opaque Asymmetric Cryptography
 * 
 * Since the amount of data that can (or should) be encrypted or signed using
 * asymmetric keys is limited by the key size, asymmetric key operations using
 * opaque keys must be done in single function calls.
 */
/**@{*/

/**
 * \brief A function that signs a hash or short message with a private key
 *
 * \param[in] key_slot              Key slot of an asymmetric key pair
 * \param[in] alg                   A signature algorithm that is compatible
 *                                  with the type of `key`
 * \param[in] p_hash                The hash to sign
 * \param[in] hash_length           Size of the `p_hash` buffer in bytes
 * \param[out] p_signature          Buffer where the signature is to be written
 * \param[in] signature_size        Size of the `p_signature` buffer in bytes
 * \param[out] p_signature_length   On success, the number of bytes
 *                                  that make up the returned signature value
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_asymmetric_opaque_sign_t)(psa_key_slot_t key_slot,
                                                     psa_algorithm_t alg,
                                                     const uint8_t *p_hash,
                                                     size_t hash_length,
                                                     uint8_t *p_signature,
                                                     size_t signature_size,
                                                     size_t *p_signature_length);

/**
 * \brief A function that verifies the signature a hash or short message using
 * an asymmetric public key
 *
 * \param[in] key_slot          Key slot of a public key or an asymmetric key
 *                              pair
 * \param[in] alg               A signature algorithm that is compatible with
 *                              the type of `key`
 * \param[in] p_hash            The hash whose signature is to be verified
 * \param[in] hash_length       Size of the `p_hash` buffer in bytes
 * \param[in] p_signature       Buffer containing the signature to verify
 * \param[in] signature_length  Size of the `p_signature` buffer in bytes
 *
 * \retval PSA_SUCCESS
 *         The signature is valid.
 */
typedef psa_status_t (*pcd_asymmetric_opaque_verify_t)(psa_key_slot_t key_slot,
                                                       psa_algorithm_t alg,
                                                       const uint8_t *p_hash,
                                                       size_t hash_length,
                                                       const uint8_t *p_signature,
                                                       size_t signature_length);

/**
 * \brief A function that encrypts a short message with an asymmetric public
 * key
 *
 * \param[in] key_slot          Key slot of a public key or an asymmetric key
 *                              pair
 * \param[in] alg               An asymmetric encryption algorithm that is
 *                              compatible with the type of `key`
 * \param[in] p_input           The message to encrypt
 * \param[in] input_length      Size of the `p_input` buffer in bytes
 * \param[in] p_salt            A salt or label, if supported by the
 *                              encryption algorithm
 *                              If the algorithm does not support a
 *                              salt, pass `NULL`.
 *                              If the algorithm supports an optional
 *                              salt and you do not want to pass a salt,
 *                              pass `NULL`.
 *                              For #PSA_ALG_RSA_PKCS1V15_CRYPT, no salt is
 *                              supported.
 * \param[in] salt_length       Size of the `p_salt` buffer in bytes
 *                              If `p_salt` is `NULL`, pass 0.
 * \param[out] p_output         Buffer where the encrypted message is to
 *                              be written
 * \param[in] output_size       Size of the `p_output` buffer in bytes
 * \param[out] p_output_length  On success, the number of bytes that make up
 *                              the returned output
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_asymmetric_opaque_encrypt_t)(psa_key_slot_t key_slot,
                                                        psa_algorithm_t alg,
                                                        const uint8_t *p_input,
                                                        size_t input_length,
                                                        const uint8_t *p_salt,
                                                        size_t salt_length,
                                                        uint8_t *p_output,
                                                        size_t output_size,
                                                        size_t *p_output_length);

/**
 * \brief Decrypt a short message with an asymmetric private key.
 *
 * \param[in] key_slot          Key slot of an asymmetric key pair
 * \param[in] alg               An asymmetric encryption algorithm that is
 *                              compatible with the type of `key`
 * \param[in] p_input           The message to decrypt
 * \param[in] input_length      Size of the `p_input` buffer in bytes
 * \param[in] p_salt            A salt or label, if supported by the
 *                              encryption algorithm
 *                              If the algorithm does not support a
 *                              salt, pass `NULL`.
 *                              If the algorithm supports an optional
 *                              salt and you do not want to pass a salt,
 *                              pass `NULL`.
 *                              For #PSA_ALG_RSA_PKCS1V15_CRYPT, no salt is
 *                              supported.
 * \param[in] salt_length       Size of the `p_salt` buffer in bytes
 *                              If `p_salt` is `NULL`, pass 0.
 * \param[out] p_output         Buffer where the decrypted message is to
 *                              be written
 * \param[in] output_size       Size of the `p_output` buffer in bytes
 * \param[out] p_output_length  On success, the number of bytes
 *                              that make up the returned output
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_asymmetric_opaque_decrypt_t)(psa_key_slot_t key_slot,
                                                        psa_algorithm_t alg,
                                                        const uint8_t *p_input,
                                                        size_t input_length,
                                                        const uint8_t *p_salt,
                                                        size_t salt_length,
                                                        uint8_t *p_output,
                                                        size_t output_size,
                                                        size_t *p_output_length);

/**
 * \brief A struct containing all of the function pointers needed to implement
 * asymmetric cryptographic operations using opaque keys.
 * 
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup.
 * 
 * If one of the functions is not implemented, it should be set to NULL.
 */
struct pcd_asymmetric_opaque_t {
    /** Function that performs the asymmetric sign operation */
    pcd_asymmetric_opaque_sign_t    *p_sign;
    /** Function that performs the asymmetric verify operation */
    pcd_asymmetric_opaque_verify_t  *p_verify;
    /** Function that performs the asymmetric encrypt operation */
    pcd_asymmetric_opaque_encrypt_t *p_encrypt;
    /** Function that performs the asymmetric decrypt operation */
    pcd_asymmetric_opaque_decrypt_t *p_decrypt;
};

/**@}*/

/** \defgroup transparent_asymmetric Transparent Asymmetric Cryptography
 *
 * Since the amount of data that can (or should) be encrypted or signed using
 * asymmetric keys is limited by the key size, asymmetric key operations using
 * transparent keys must be done in single function calls.
 */
/**@{*/


/**
 * \brief A function that signs a hash or short message with a transparent
 * asymmetric private key
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_asymmetric_<ALGO>_sign
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the signing algorithm
 * 
 * \param[in] p_key                 A buffer containing the private key
 *                                  material
 * \param[in] key_size              The size in bytes of the `p_key` data
 * \param[in] alg                   A signature algorithm that is compatible
 *                                  with the type of `p_key`
 * \param[in] p_hash                The hash or message to sign
 * \param[in] hash_length           Size of the `p_hash` buffer in bytes
 * \param[out] p_signature          Buffer where the signature is to be written
 * \param[in] signature_size        Size of the `p_signature` buffer in bytes
 * \param[out] p_signature_length   On success, the number of bytes
 *                                  that make up the returned signature value
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_asymmetric_transparent_sign_t)(const uint8_t *p_key,
                                                          size_t key_size,
                                                          psa_algorithm_t alg,
                                                          const uint8_t *p_hash,
                                                          size_t hash_length,
                                                          uint8_t *p_signature,
                                                          size_t signature_size,
                                                          size_t *p_signature_length);

/**
 * \brief A function that verifies the signature a hash or short message using
 * a transparent asymmetric public key
 *
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_asymmetric_<ALGO>_verify
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the signing algorithm 
 * 
 * \param[in] p_key             A buffer containing the public key material
 * \param[in] key_size          The size in bytes of the `p_key` data
 * \param[in] alg               A signature algorithm that is compatible with
 *                              the type of `key`
 * \param[in] p_hash            The hash or message whose signature is to be
 *                              verified
 * \param[in] hash_length       Size of the `p_hash` buffer in bytes
 * \param[in] p_signature       Buffer containing the signature to verify
 * \param[in] signature_length  Size of the `p_signature` buffer in bytes
 *
 * \retval PSA_SUCCESS
 *         The signature is valid.
 */
typedef psa_status_t (*pcd_asymmetric_transparent_verify_t)(const uint8_t *p_key,
                                                            size_t key_size,
                                                            psa_algorithm_t alg,
                                                            const uint8_t *p_hash,
                                                            size_t hash_length,
                                                            const uint8_t *p_signature,
                                                            size_t signature_length);

/**
 * \brief A function that encrypts a short message with a transparent
 * asymmetric public key
 *
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_asymmetric_<ALGO>_encrypt
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the encryption algorithm
 * 
 * \param[in] p_key             A buffer containing the public key material
 * \param[in] key_size          The size in bytes of the `p_key` data
 * \param[in] alg               An asymmetric encryption algorithm that is
 *                              compatible with the type of `key`
 * \param[in] p_input           The message to encrypt
 * \param[in] input_length      Size of the `p_input` buffer in bytes
 * \param[in] p_salt            A salt or label, if supported by the
 *                              encryption algorithm
 *                              If the algorithm does not support a
 *                              salt, pass `NULL`
 *                              If the algorithm supports an optional
 *                              salt and you do not want to pass a salt,
 *                              pass `NULL`.
 *                              For #PSA_ALG_RSA_PKCS1V15_CRYPT, no salt is
 *                              supported.
 * \param[in] salt_length       Size of the `p_salt` buffer in bytes
 *                              If `p_salt` is `NULL`, pass 0.
 * \param[out] p_output         Buffer where the encrypted message is to
 *                              be written
 * \param[in] output_size       Size of the `p_output` buffer in bytes
 * \param[out] p_output_length  On success, the number of bytes
 *                              that make up the returned output
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_asymmetric_transparent_encrypt_t)(const uint8_t *p_key,
                                                             size_t key_size,
                                                             psa_algorithm_t alg,
                                                             const uint8_t *p_input,
                                                             size_t input_length,
                                                             const uint8_t *p_salt,
                                                             size_t salt_length,
                                                             uint8_t *p_output,
                                                             size_t output_size,
                                                             size_t *p_output_length);

/**
 * \brief Decrypt a short message with a transparent asymmetric private key
 *
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_asymmetric_<ALGO>_decrypt
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the encryption algorithm
 * 
 * \param[in] p_key             A buffer containing the private key material
 * \param[in] key_size          The size in bytes of the `p_key` data
 * \param[in] alg               An asymmetric encryption algorithm that is
 *                              compatible with the type of `key`
 * \param[in] p_input           The message to decrypt
 * \param[in] input_length      Size of the `p_input` buffer in bytes
 * \param[in] p_salt            A salt or label, if supported by the
 *                              encryption algorithm
 *                              If the algorithm does not support a
 *                              salt, pass `NULL`.
 *                              If the algorithm supports an optional
 *                              salt and you do not want to pass a salt,
 *                              pass `NULL`.
 *                              For #PSA_ALG_RSA_PKCS1V15_CRYPT, no salt is
 *                              supported
 * \param[in] salt_length       Size of the `p_salt` buffer in bytes
 *                              If `p_salt` is `NULL`, pass 0
 * \param[out] p_output         Buffer where the decrypted message is to
 *                              be written
 * \param[in] output_size       Size of the `p_output` buffer in bytes
 * \param[out] p_output_length  On success, the number of bytes
 *                              that make up the returned output
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_asymmetric_transparent_decrypt_t)(const uint8_t *p_key,
                                                             size_t key_size,
                                                             psa_algorithm_t alg,
                                                             const uint8_t *p_input,
                                                             size_t input_length,
                                                             const uint8_t *p_salt,
                                                             size_t salt_length,
                                                             uint8_t *p_output,
                                                             size_t output_size,
                                                             size_t *p_output_length);

/**@}*/

/** \defgroup aead_opaque AEAD Opaque
 * Authenticated Encryption with Additional Data (AEAD) operations with opaque
 * keys must be done in one function call. While this creates a burden for 
 * implementers as there must be sufficient space in memory for the entire
 * message, it prevents decrypted data from being made available before the
 * authentication operation is complete and the data is known to be authentic.
 */
/**@{*/

/** \brief Process an authenticated encryption operation using an opaque key
 *
 * \param[in] key_slot                  Slot containing the key to use.
 * \param[in] algorithm                 The AEAD algorithm to compute
 *                                      (\c PSA_ALG_XXX value such that
 *                                      #PSA_ALG_IS_AEAD(`alg`) is true)
 * \param[in] p_nonce                   Nonce or IV to use
 * \param[in] nonce_length              Size of the `p_nonce` buffer in bytes
 * \param[in] p_additional_data         Additional data that will be
 *                                      authenticated but not encrypted
 * \param[in] additional_data_length    Size of `p_additional_data` in bytes
 * \param[in] p_plaintext               Data that will be authenticated and
 *                                      encrypted
 * \param[in] plaintext_length          Size of `p_plaintext` in bytes
 * \param[out] p_ciphertext             Output buffer for the authenticated and
 *                                      encrypted data. The additional data is
 *                                      not part of this output. For algorithms
 *                                      where the encrypted data and the
 *                                      authentication tag are defined as
 *                                      separate outputs, the authentication
 *                                      tag is appended to the encrypted data.
 * \param[in] ciphertext_size           Size of the `p_ciphertext` buffer in
 *                                      bytes
 * \param[out] p_ciphertext_length      On success, the size of the output in
 *                                      the `p_ciphertext` buffer
 *
 * \retval #PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*psa_aead_opaque_encrypt_t)(psa_key_slot_t key_slot,
                                                  psa_algorithm_t algorithm,
                                                  const uint8_t *p_nonce,
                                                  size_t nonce_length,
                                                  const uint8_t *p_additional_data,
                                                  size_t additional_data_length,
                                                  const uint8_t *p_plaintext,
                                                  size_t plaintext_length,
                                                  uint8_t *p_ciphertext,
                                                  size_t ciphertext_size,
                                                  size_t *p_ciphertext_length);

/** Process an authenticated decryption operation using an opaque key
 *
 * \param[in] key_slot                  Slot containing the key to use
 * \param[in] algorithm                 The AEAD algorithm to compute
 *                                      (\c PSA_ALG_XXX value such that
 *                                      #PSA_ALG_IS_AEAD(`alg`) is true)
 * \param[in] p_nonce                   Nonce or IV to use
 * \param[in] nonce_length              Size of the `p_nonce` buffer in bytes
 * \param[in] p_additional_data         Additional data that has been
 *                                      authenticated but not encrypted
 * \param[in] additional_data_length    Size of `p_additional_data` in bytes
 * \param[in] p_ciphertext              Data that has been authenticated and
 *                                      encrypted.
 *                                      For algorithms where the encrypted data
 *                                      and the authentication tag are defined
 *                                      as separate inputs, the buffer must
 *                                      contain the encrypted data followed by
 *                                      the authentication tag.
 * \param[in] ciphertext_length         Size of `p_ciphertext` in bytes
 * \param[out] p_plaintext              Output buffer for the decrypted data
 * \param[in] plaintext_size            Size of the `p_plaintext` buffer in
 *                                      bytes
 * \param[out] p_plaintext_length       On success, the size of the output in
 *                                      the `p_plaintext` buffer
 *
 * \retval #PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*psa_aead_opaque_decrypt_t)(psa_key_slot_t key_slot,
                                                  psa_algorithm_t algorithm,
                                                  const uint8_t *p_nonce,
                                                  size_t nonce_length,
                                                  const uint8_t *p_additional_data,
                                                  size_t additional_data_length,
                                                  const uint8_t *p_ciphertext,
                                                  size_t ciphertext_length,
                                                  uint8_t *p_plaintext,
                                                  size_t plaintext_size,
                                                  size_t *p_plaintext_length);

/**
 * \brief A struct containing all of the function pointers needed to implement
 * Authenticated Encryption with Additional Data operations using opaque keys
 * 
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup.
 * 
 * If one of the functions is not implemented, it should be set to NULL.
 */
struct psa_aead_opaque_t {
    /** Function that performs the AEAD encrypt operation */
    psa_aead_opaque_encrypt_t *p_encrypt;
    /** Function that performs the AEAD decrypt operation */
    psa_aead_opaque_decrypt_t *p_decrypt;
};
/**@}*/

/** \defgroup aead_transparent AEAD Transparent
 * 
 * Authenticated Encryption with Additional Data (AEAD) operations with
 * transparent keys must be done in one function call. While this creates a
 * burden for implementers as there must be sufficient space in memory for the
 * entire message, it prevents decrypted data from being made available before
 * the authentication operation is complete and the data is known to be
 * authentic.
 */
/**@{*/

/** Process an authenticated encryption operation using an opaque key.
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_aead_<ALGO>_encrypt
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the AEAD algorithm
 *
 * \param[in] p_key                     A pointer to the key material
 * \param[in] key_length                The size in bytes of the key material
 * \param[in] alg                       The AEAD algorithm to compute
 *                                      (\c PSA_ALG_XXX value such that
 *                                      #PSA_ALG_IS_AEAD(`alg`) is true)
 * \param[in] nonce                     Nonce or IV to use
 * \param[in] nonce_length              Size of the `nonce` buffer in bytes
 * \param[in] additional_data           Additional data that will be MACed
 *                                      but not encrypted.
 * \param[in] additional_data_length    Size of `additional_data` in bytes
 * \param[in] plaintext                 Data that will be MACed and
 *                                      encrypted.
 * \param[in] plaintext_length          Size of `plaintext` in bytes
 * \param[out] ciphertext               Output buffer for the authenticated and
 *                                      encrypted data. The additional data is
 *                                      not part of this output. For algorithms
 *                                      where the encrypted data and the
 *                                      authentication tag are defined as
 *                                      separate outputs, the authentication
 *                                      tag is appended to the encrypted data.
 * \param[in] ciphertext_size           Size of the `ciphertext` buffer in
 *                                      bytes
 *                                      This must be at least
 *                                      #PSA_AEAD_ENCRYPT_OUTPUT_SIZE(`alg`,
 *                                      `plaintext_length`).
 * \param[out] ciphertext_length        On success, the size of the output in
 *                                      the `ciphertext` buffer
 *
 * \retval #PSA_SUCCESS
 
 */
typedef psa_status_t (*psa_aead_transparent_encrypt_t)(const uint8_t *p_key,
                                                       size_t key_length,
                                                       psa_algorithm_t alg,
                                                       const uint8_t *nonce,
                                                       size_t nonce_length,
                                                       const uint8_t *additional_data,
                                                       size_t additional_data_length,
                                                       const uint8_t *plaintext,
                                                       size_t plaintext_length,
                                                       uint8_t *ciphertext,
                                                       size_t ciphertext_size,
                                                       size_t *ciphertext_length);

/** Process an authenticated decryption operation using an opaque key.
 * 
 * Functions that implement the prototype should be named in the following
 * convention:
 * ~~~~~~~~~~~~~{.c}
 * pcd_aead_<ALGO>_decrypt
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the AEAD algorithm
 * \param[in] p_key                     A pointer to the key material
 * \param[in] key_length                The size in bytes of the key material
 * \param[in] alg                       The AEAD algorithm to compute
 *                                      (\c PSA_ALG_XXX value such that
 *                                      #PSA_ALG_IS_AEAD(`alg`) is true)
 * \param[in] nonce                     Nonce or IV to use
 * \param[in] nonce_length              Size of the `nonce` buffer in bytes
 * \param[in] additional_data           Additional data that has been MACed
 *                                      but not encrypted
 * \param[in] additional_data_length    Size of `additional_data` in bytes
 * \param[in] ciphertext                Data that has been MACed and
 *                                      encrypted
 *                                      For algorithms where the encrypted data
 *                                      and the authentication tag are defined
 *                                      as separate inputs, the buffer must
 *                                      contain the encrypted data followed by
 *                                      the authentication tag.
 * \param[in] ciphertext_length         Size of `ciphertext` in bytes
 * \param[out] plaintext                Output buffer for the decrypted data
 * \param[in] plaintext_size            Size of the `plaintext` buffer in
 *                                      bytes
 *                                      This must be at least
 *                                      #PSA_AEAD_DECRYPT_OUTPUT_SIZE(`alg`,
 *                                      `ciphertext_length`).
 * \param[out] plaintext_length         On success, the size of the output
 *                                      in the \b plaintext buffer
 *
 * \retval #PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*psa_aead_transparent_decrypt_t)(const uint8_t *p_key,
                                                       size_t key_length,
                                                       psa_algorithm_t alg,
                                                       const uint8_t *nonce,
                                                       size_t nonce_length,
                                                       const uint8_t *additional_data,
                                                       size_t additional_data_length,
                                                       const uint8_t *ciphertext,
                                                       size_t ciphertext_length,
                                                       uint8_t *plaintext,
                                                       size_t plaintext_size,
                                                       size_t *plaintext_length);

/**@}*/


/** \defgroup driver_rng Entropy Generation
 */
/**@{*/

/** \brief A hardware-specific structure for a entropy providing hardware
 */
typedef struct pcd_entropy_context_s pcd_entropy_context_t;

/** \brief Initialize an entropy driver
 *
 * 
 * \param[in,out] p_context             A hardware-specific structure
 *                                      containing any context information for
 *                                      the implementation
 *
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_entropy_init_t)(pcd_entropy_context_t *p_context);

/** \brief Get a specified number of bytes from the entropy source
 * 
 * It retrives `buffer_size` bytes of data from the entropy source. The entropy
 * source will always fill the provided buffer to its full size, however, most
 * entropy sources have biases, and the actual amount of entropy contained in
 * the buffer will be less than the number of bytes.
 * The driver will return the actual number of bytes of entropy placed in the
 * buffer in `p_received_entropy_bytes`.
 * A PSA Crypto API implementation will likely feed the output of this function
 * into a Digital Random Bit Generator (DRBG), and typically has a minimum
 * amount of entropy that it needs.
 * To accomplish this, the PSA Crypto implementation should be designed to call
 * this function multiple times until it has received the required amount of
 * entropy from the entropy source.
 * 
 * \param[in,out] p_context                 A hardware-specific structure
 *                                          containing any context information
 *                                          for the implementation
 * \param[out] p_buffer                     A caller-allocated buffer for the
 *                                          retrieved bytes to be placed in
 * \param[in] buffer_size                   The allocated size of `p_buffer`
 * \param[out] p_received_entropy_bytes     The amount of entropy (in bytes)
 *                                          actually provided in `p_buffer`
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_entropy_get_bytes_t)(pcd_entropy_context_t *p_context,
                                                uint8_t *p_buffer,
                                                uint32_t buffer_size,
                                                uint32_t *p_received_entropy_bytes);

/**
 * \brief A struct containing all of the function pointers needed to interface
 * to an entropy source
 * 
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup.
 * 
 * If one of the functions is not implemented, it should be set to NULL.
 */
struct pcd_entropy_t {
    /** Function that performs initialization for the entropy source */
    pcd_entropy_init_t *p_init;
    /** Function that performs the get_bytes operation for the entropy source
    */
    pcd_entropy_get_bytes_t *p_get_bytes;
};
/**@}*/

/** \defgroup driver_key_management Key Management
 * Currently, key management is limited to importing keys in the clear,
 * destroying keys, and exporting keys in the clear.
 * Whether a key may be exported is determined by the key policies in place
 * on the key slot.
 */
/**@{*/

/** \brief Import a key in binary format
 *
 * This function can support any output from psa_export_key(). Refer to the
 * documentation of psa_export_key() for the format for each key type.
 *
 * \param[in] key_slot      Slot where the key will be stored
 *                          This must be a valid slot for a key of the chosen
 *                          type. It must be unoccupied.
 * \param[in] type          Key type (a \c PSA_KEY_TYPE_XXX value)
 * \param[in] algorithm     Key algorithm (a \c PSA_ALG_XXX value)
 * \param[in] usage         The allowed uses of the key
 * \param[in] p_data        Buffer containing the key data
 * \param[in] data_length   Size of the `data` buffer in bytes
 *
 * \retval #PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*pcd_opaque_import_key_t)(psa_key_slot_t key_slot,
                                                psa_key_type_t type,
                                                psa_algorithm_t algorithm,
                                                psa_key_usage_t usage,
                                                const uint8_t *p_data,
                                                size_t data_length);

/**
 * \brief Destroy a key and restore the slot to its default state
 *
 * This function destroys the content of the key slot from both volatile
 * memory and, if applicable, non-volatile storage. Implementations shall
 * make a best effort to ensure that any previous content of the slot is
 * unrecoverable.
 *
 * This function also erases any metadata such as policies. It returns the
 * specified slot to its default state.
 *
 * \param[in] key_slot        The key slot to erase.
 *
 * \retval #PSA_SUCCESS
 *         The slot's content, if any, has been erased.
 */
typedef psa_status_t (*pcd_destroy_key_t)(psa_key_slot_t key);

/**
 * \brief Export a key in binary format
 *
 * The output of this function can be passed to psa_import_key() to
 * create an equivalent object.
 *
 * If a key is created with `psa_import_key()` and then exported with
 * this function, it is not guaranteed that the resulting data is
 * identical: the implementation may choose a different representation
 * of the same key if the format permits it.
 *
 * For standard key types, the output format is as follows:
 *
 * - For symmetric keys (including MAC keys), the format is the
 *   raw bytes of the key.
 * - For DES, the key data consists of 8 bytes. The parity bits must be
 *   correct.
 * - For Triple-DES, the format is the concatenation of the
 *   two or three DES keys.
 * - For RSA key pairs (#PSA_KEY_TYPE_RSA_KEYPAIR), the format
 *   is the non-encrypted DER representation defined by PKCS\#1 (RFC 8017)
 *   as RSAPrivateKey.
 * - For RSA public keys (#PSA_KEY_TYPE_RSA_PUBLIC_KEY), the format
 *   is the DER representation defined by RFC 5280 as SubjectPublicKeyInfo.
 *
 * \param[in] key               Slot whose content is to be exported. This must
 *                              be an occupied key slot.
 * \param[out] p_data           Buffer where the key data is to be written.
 * \param[in] data_size         Size of the `p_data` buffer in bytes.
 * \param[out] p_data_length    On success, the number of bytes
 *                              that make up the key data.
 *
 * \retval #PSA_SUCCESS
 * \retval #PSA_ERROR_EMPTY_SLOT
 * \retval #PSA_ERROR_NOT_PERMITTED
 * \retval #PSA_ERROR_NOT_SUPPORTED
 * \retval #PSA_ERROR_COMMUNICATION_FAILURE
 * \retval #PSA_ERROR_HARDWARE_FAILURE
 * \retval #PSA_ERROR_TAMPERING_DETECTED
 */
typedef psa_status_t (*pcd_export_key_t)(psa_key_slot_t key,
                                         uint8_t *p_data,
                                         size_t data_size,
                                         size_t *p_data_length);

/**
 * \brief Export a public key or the public part of a key pair in binary format
 *
 * The output of this function can be passed to psa_import_key() to
 * create an object that is equivalent to the public key.
 *
 * For standard key types, the output format is as follows:
 *
 * - For RSA keys (#PSA_KEY_TYPE_RSA_KEYPAIR or #PSA_KEY_TYPE_RSA_PUBLIC_KEY),
 *   the format is the DER representation of the public key defined by RFC 5280
 *   as SubjectPublicKeyInfo.
 *
 * \param[in] key_slot          Slot whose content is to be exported. This must
 *                              be an occupied key slot.
 * \param[out] p_data           Buffer where the key data is to be written.
 * \param[in] data_size         Size of the `data` buffer in bytes.
 * \param[out] p_data_length    On success, the number of bytes
 *                              that make up the key data.
 *
 * \retval #PSA_SUCCESS
 */
typedef psa_status_t (*pcd_export_public_key_t)(psa_key_slot_t key,
                                                uint8_t *p_data,
                                                size_t data_size,
                                                size_t *p_data_length);

/**
 * \brief A struct containing all of the function pointers needed to for key
 * management using opaque keys
 * 
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup.
 * 
 * If one of the functions is not implemented, it should be set to NULL.
 */
struct pcd_key_management_t {
    /** Function that performs the key import operation */
    pcd_opaque_import_key_t *p_import;
    /** Function that performs the key destroy operation */
    pcd_destroy_key_t       *p_destroy;
    /** Function that performs the key export operation */
    pcd_export_key_t        *p_export;
    /** Function that perforsm the public key export operation */
    pcd_export_public_key_t *p_export_public;
};

/**@}*/

/** \defgroup driver_derivation Key Derivation and Agreement
 * Key derivation is the process of generating new key material using an
 * existing key and additional parameters, iterating through a basic
 * cryptographic function, such as a hash.
 * Key agreement is a part of cryptographic protocols that allows two parties
 * to agree on the same key value, but starting from different original key
 * material.
 * The flows are similar, and the PSA Crypto Driver API uses the same functions
 * for both of the flows.
 * 
 * There are two different final functions for the flows,
 * `pcd_key_derivation_derive` and `pcd_key_derivation_export`.
 * `pcd_key_derivation_derive` is used when the key material should be placed
 * in a slot on the hardware and not exposed to the caller.
 * `pcd_key_derivation_export` is used when the key material should be returned
 * to the PSA Cryptographic API implementation.
 * 
 * Different key derivation algorithms require a different number of inputs.
 * Instead of having an API that takes as input variable length arrays, which
 * can be problemmatic to manage on embedded platforms, the inputs are passed
 * to the driver via a function, `pcd_key_derivation_collateral`, that is
 * called multiple times with different `collateral_id`s. Thus, for a key
 * derivation algorithm that required 3 paramter inputs, the flow would look
 * something like:
 * ~~~~~~~~~~~~~{.c}
 * pcd_key_derivation_setup(kdf_algorithm, source_key, dest_key_size_bytes);
 * pcd_key_derivation_collateral(kdf_algorithm_collateral_id_0,
 *                               p_collateral_0,
 *                               collateral_0_size);
 * pcd_key_derivation_collateral(kdf_algorithm_collateral_id_1,
 *                               p_collateral_1,
 *                               collateral_1_size);
 * pcd_key_derivation_collateral(kdf_algorithm_collateral_id_2,
 *                               p_collateral_2,
 *                               collateral_2_size);
 * pcd_key_derivation_derive();
 * ~~~~~~~~~~~~~
 * 
 * key agreement example:
 * ~~~~~~~~~~~~~{.c}
 * pcd_key_derivation_setup(alg, source_key. dest_key_size_bytes);
 * pcd_key_derivation_collateral(DHE_PUBKEY, p_pubkey, pubkey_size);
 * pcd_key_derivation_export(p_session_key,
 *                           session_key_size,
 *                           &session_key_length);
 * ~~~~~~~~~~~~~
 */
/**@{*/

/** \brief The hardware-specific key derivation context structure
 * 
 * The contents of this structure are implementation dependent and are
 * therefore not described here
 */
typedef struct pcd_key_derivation_context_s pcd_key_derivation_context_t;

/** \brief Set up a key derivation operation by specifying the algorithm and
 * the source key sot
 * 
 * \param[in,out] p_context A hardware-specific structure containing any
 *                          context information for the implementation
 * \param[in] kdf_alg       The algorithm to be used for the key derivation
 * \param[in] souce_key     The key to be used as the source material for the
 *                          key derivation
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_key_derivation_setup_t)(pcd_key_derivation_context_t *p_context,
                                                   psa_algorithm_t kdf_alg,
                                                   psa_key_slot_t source_key);

/** \brief Provide collateral (parameters) needed for a key derivation or key
 * agreement operation
 * 
 * Since many key derivation algorithms require multiple parameters, it is
 * expeced that this function may be called multiple times for the same
 * operation, each with a different algorithm-specific `collateral_id`
 * 
 * \param[in,out] p_context     A hardware-specific structure containing any
 *                              context information for the implementation
 * \param[in] collateral_id     An ID for the collateral being provided
 * \param[in] p_collateral      A buffer containing the collateral data
 * \param[in] collateral_size   The size in bytes of the collateral
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_key_derivation_collateral_t)(pcd_key_derivation_context_t *p_context,
                                                         uint32_t collateral_id,
                                                         const uint8_t *p_collateral,
                                                         size_t collateral_size);

/** \brief Perform the final key derivation step and place the generated key
 * material in a slot
 * \param[in,out] p_context     A hardware-specific structure containing any
 *                              context information for the implementation
 * \param[in] dest_key          The slot where the generated key material
 *                              should be placed
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_key_derivation_derive_t)(pcd_key_derivation_context_t *p_context,
                                                    psa_key_slot_t dest_key);

/** \brief Perform the final step of a key agreement and place the generated
 * key material in a buffer
 * 
 * \param[out] p_output         Buffer in which to place the generated key
 *                              material
 * \param[in] output_size       The size in bytes of `p_output`
 * \param[out] p_output_length  Upon success, contains the number of bytes of
 *                              key material placed in `p_output`
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_key_derivation_export_t)(uint8_t *p_output,
                                                    size_t output_size,
                                                    size_t *p_output_length);

/**
 * \brief A struct containing all of the function pointers needed to for key
 * derivation and agreement
 * 
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup.
 * 
 * If one of the functions is not implemented, it should be set to NULL.
 */
struct pcd_key_derivation_t {
    /** Function that performs the key derivation setup */
    pcd_key_derivation_setup_t      *p_setup;
    /** Function that sets the key derivation collateral */
    pcd_key_derivation_collateral_t *p_collateral;
    /** Function that performs the final key derivation step */
    pcd_key_derivation_derive_t     *p_derive;
    /** Function that perforsm the final key derivation or agreement and
     * exports the key */
    pcd_key_derivation_export_t     *p_export;
};

/**@}*/

#endif // __PSA_CRYPTO_DRIVER_H__