include/psa/crypto_se_driver.h

/**
 * \file psa/crypto_se_driver.h
 * \brief PSA external cryptoprocessor driver module
 *
 * This header declares types and function signatures for cryptography
 * drivers that access key material via opaque references.
 * This is meant for cryptoprocessors that have a separate key storage from the
 * space in which the PSA Crypto implementation runs, typically secure
 * elements (SEs).
 *
 * This file is part of the PSA Crypto Driver HAL (hardware abstraction layer),
 * containing functions for driver developers to implement to enable hardware
 * to be called in a standardized way by a PSA Cryptography API
 * implementation. The functions comprising the driver HAL, which driver
 * authors implement, are not intended to be called by application developers.
 */

/*
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 */
#ifndef PSA_CRYPTO_SE_DRIVER_H
#define PSA_CRYPTO_SE_DRIVER_H
#include "mbedtls/private_access.h"

#include "crypto_driver_common.h"

#ifdef __cplusplus
extern "C" {
#endif

/** \defgroup se_init Secure element driver initialization
 */
/**@{*/

/** \brief Driver context structure
 *
 * Driver functions receive a pointer to this structure.
 * Each registered driver has one instance of this structure.
 *
 * Implementations must include the fields specified here and
 * may include other fields.
 */
typedef struct {
    /** A read-only pointer to the driver's persistent data.
     *
     * Drivers typically use this persistent data to keep track of
     * which slot numbers are available. This is only a guideline:
     * drivers may use the persistent data for any purpose, keeping
     * in mind the restrictions on when the persistent data is saved
     * to storage: the persistent data is only saved after calling
     * certain functions that receive a writable pointer to the
     * persistent data.
     *
     * The core allocates a memory buffer for the persistent data.
     * The pointer is guaranteed to be suitably aligned for any data type,
     * like a pointer returned by `malloc` (but the core can use any
     * method to allocate the buffer, not necessarily `malloc`).
     *
     * The size of this buffer is in the \c persistent_data_size field of
     * this structure.
     *
     * Before the driver is initialized for the first time, the content of
     * the persistent data is all-bits-zero. After a driver upgrade, if the
     * size of the persistent data has increased, the original data is padded
     * on the right with zeros; if the size has decreased, the original data
     * is truncated to the new size.
     *
     * This pointer is to read-only data. Only a few driver functions are
     * allowed to modify the persistent data. These functions receive a
     * writable pointer. These functions are:
     * - psa_drv_se_t::p_init
     * - psa_drv_se_key_management_t::p_allocate
     * - psa_drv_se_key_management_t::p_destroy
     *
     * The PSA Cryptography core saves the persistent data from one
     * session to the next. It does this before returning from API functions
     * that call a driver method that is allowed to modify the persistent
     * data, specifically:
     * - psa_crypto_init() causes a call to psa_drv_se_t::p_init, and may call
     *   psa_drv_se_key_management_t::p_destroy to complete an action
     *   that was interrupted by a power failure.
     * - Key creation functions cause a call to
     *   psa_drv_se_key_management_t::p_allocate, and may cause a call to
     *   psa_drv_se_key_management_t::p_destroy in case an error occurs.
     * - psa_destroy_key() causes a call to
     *   psa_drv_se_key_management_t::p_destroy.
     */
    const void *const MBEDTLS_PRIVATE(persistent_data);

    /** The size of \c persistent_data in bytes.
     *
     * This is always equal to the value of the `persistent_data_size` field
     * of the ::psa_drv_se_t structure when the driver is registered.
     */
    const size_t MBEDTLS_PRIVATE(persistent_data_size);

    /** Driver transient data.
     *
     * The core initializes this value to 0 and does not read or modify it
     * afterwards. The driver may store whatever it wants in this field.
     */
    uintptr_t MBEDTLS_PRIVATE(transient_data);
} psa_drv_se_context_t;

/** \brief A driver initialization function.
 *
 * \param[in,out] drv_context       The driver context structure.
 * \param[in,out] persistent_data   A pointer to the persistent data
 *                                  that allows writing.
 * \param location                  The location value for which this driver
 *                                  is registered. The driver will be invoked
 *                                  for all keys whose lifetime is in this
 *                                  location.
 *
 * \retval #PSA_SUCCESS
 *         The driver is operational.
 *         The core will update the persistent data in storage.
 * \return
 *         Any other return value prevents the driver from being used in
 *         this session.
 *         The core will NOT update the persistent data in storage.
 */
typedef psa_status_t (*psa_drv_se_init_t)(psa_drv_se_context_t *drv_context,
                                          void *persistent_data,
                                          psa_key_location_t location);

#if defined(__DOXYGEN_ONLY__) || !defined(MBEDTLS_PSA_CRYPTO_SE_C)
/* Mbed TLS with secure element support enabled defines this type in
 * crypto_types.h because it is also visible to applications through an
 * implementation-specific extension.
 * For the PSA Cryptography specification, this type is only visible
 * via crypto_se_driver.h. */
/** An internal designation of a key slot between the core part of the
 * PSA Crypto implementation and the driver. The meaning of this value
 * is driver-dependent. */
typedef uint64_t psa_key_slot_number_t;
#endif /* __DOXYGEN_ONLY__ || !MBEDTLS_PSA_CRYPTO_SE_C */

/**@}*/

/** \defgroup se_mac Secure Element Message Authentication Codes
 * Generation and authentication of Message Authentication Codes (MACs) using
 * a secure element can be done either as a single function call (via the
 * `psa_drv_se_mac_generate_t` or `psa_drv_se_mac_verify_t` functions), or in
 * parts using the following sequence:
 * - `psa_drv_se_mac_setup_t`
 * - `psa_drv_se_mac_update_t`
 * - `psa_drv_se_mac_update_t`
 * - ...
 * - `psa_drv_se_mac_finish_t` or `psa_drv_se_mac_finish_verify_t`
 *
 * If a previously started secure element MAC operation needs to be terminated,
 * it should be done so by the `psa_drv_se_mac_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 secure element  MAC operation for a PSA
 * Crypto Driver implementation
 *
 * \param[in,out] drv_context   The driver context structure.
 * \param[in,out] op_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 (*psa_drv_se_mac_setup_t)(psa_drv_se_context_t *drv_context,
                                               void *op_context,
                                               psa_key_slot_number_t key_slot,
                                               psa_algorithm_t algorithm);

/** \brief A function that continues a previously started secure element MAC
 * operation
 *
 * \param[in,out] op_context    A hardware-specific structure for the
 *                              previously-established MAC operation to be
 *                              updated
 * \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 (*psa_drv_se_mac_update_t)(void *op_context,
                                                const uint8_t *p_input,
                                                size_t input_length);

/** \brief a function that completes a previously started secure element MAC
 * operation by returning the resulting MAC.
 *
 * \param[in,out] op_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 (*psa_drv_se_mac_finish_t)(void *op_context,
                                                uint8_t *p_mac,
                                                size_t mac_size,
                                                size_t *p_mac_length);

/** \brief A function that completes a previously started secure element MAC
 * operation by comparing the resulting MAC against a provided value
 *
 * \param[in,out] op_context    A hardware-specific structure for the previously
 *                              started MAC operation to be finished
 * \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 (*psa_drv_se_mac_finish_verify_t)(void *op_context,
                                                       const uint8_t *p_mac,
                                                       size_t mac_length);

/** \brief A function that aborts a previous started secure element MAC
 * operation
 *
 * \param[in,out] op_context    A hardware-specific structure for the previously
 *                              started MAC operation to be aborted
 */
typedef psa_status_t (*psa_drv_se_mac_abort_t)(void *op_context);

/** \brief A function that performs a secure element MAC operation in one
 * command and returns the calculated MAC
 *
 * \param[in,out] drv_context   The driver context structure.
 * \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 (*psa_drv_se_mac_generate_t)(psa_drv_se_context_t *drv_context,
                                                  const uint8_t *p_input,
                                                  size_t input_length,
                                                  psa_key_slot_number_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 a secure element MAC operation in one
 * command and compares the resulting MAC against a provided value
 *
 * \param[in,out] drv_context       The driver context structure.
 * \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 (*psa_drv_se_mac_verify_t)(psa_drv_se_context_t *drv_context,
                                                const uint8_t *p_input,
                                                size_t input_length,
                                                psa_key_slot_number_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
 * perform secure element MAC operations
 *
 * PSA Crypto API implementations should populate the table as appropriate
 * upon startup.
 *
 * If one of the functions is not implemented (such as
 * `psa_drv_se_mac_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`).
 *
 */
typedef struct {
    /**The size in bytes of the hardware-specific secure element MAC context
     * structure
     */
    size_t                    MBEDTLS_PRIVATE(context_size);
    /** Function that performs a MAC setup operation
     */
    psa_drv_se_mac_setup_t          MBEDTLS_PRIVATE(p_setup);
    /** Function that performs a MAC update operation
     */
    psa_drv_se_mac_update_t         MBEDTLS_PRIVATE(p_update);
    /** Function that completes a MAC operation
     */
    psa_drv_se_mac_finish_t         MBEDTLS_PRIVATE(p_finish);
    /** Function that completes a MAC operation with a verify check
     */
    psa_drv_se_mac_finish_verify_t  MBEDTLS_PRIVATE(p_finish_verify);
    /** Function that aborts a previously started MAC operation
     */
    psa_drv_se_mac_abort_t          MBEDTLS_PRIVATE(p_abort);
    /** Function that performs a MAC operation in one call
     */
    psa_drv_se_mac_generate_t       MBEDTLS_PRIVATE(p_mac);
    /** Function that performs a MAC and verify operation in one call
     */
    psa_drv_se_mac_verify_t         MBEDTLS_PRIVATE(p_mac_verify);
} psa_drv_se_mac_t;
/**@}*/

/** \defgroup se_cipher Secure Element Symmetric Ciphers
 *
 * Encryption and Decryption using secure element keys in block modes other
 * than ECB must be done in multiple parts, using the following flow:
 * - `psa_drv_se_cipher_setup_t`
 * - `psa_drv_se_cipher_set_iv_t` (optional depending upon block mode)
 * - `psa_drv_se_cipher_update_t`
 * - `psa_drv_se_cipher_update_t`
 * - ...
 * - `psa_drv_se_cipher_finish_t`
 *
 * If a previously started secure element Cipher operation needs to be
 * terminated, it should be done so by the `psa_drv_se_cipher_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 `psa_drv_se_cipher_ecb_t` function
 * for the cipher operations.
 */
/**@{*/

/** \brief A function that provides the cipher setup function for a
 * secure element driver
 *
 * \param[in,out] drv_context   The driver context structure.
 * \param[in,out] op_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 \emptydescription
 * \retval #PSA_ERROR_NOT_SUPPORTED \emptydescription
 */
typedef psa_status_t (*psa_drv_se_cipher_setup_t)(psa_drv_se_context_t *drv_context,
                                                  void *op_context,
                                                  psa_key_slot_number_t key_slot,
                                                  psa_algorithm_t algorithm,
                                                  psa_encrypt_or_decrypt_t direction);

/** \brief A function that sets the initialization vector (if
 * necessary) for a secure element cipher operation
 *
 * Rationale: The `psa_se_cipher_*` operation 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 drivers to implement as the PSA
 * Crypto implementation can do the generation using its RNG features.
 *
 * \param[in,out] op_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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_cipher_set_iv_t)(void *op_context,
                                                   const uint8_t *p_iv,
                                                   size_t iv_length);

/** \brief A function that continues a previously started secure element cipher
 * operation
 *
 * \param[in,out] op_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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_cipher_update_t)(void *op_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 secure element cipher
 * operation
 *
 * \param[in,out] op_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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_cipher_finish_t)(void *op_context,
                                                   uint8_t *p_output,
                                                   size_t output_size,
                                                   size_t *p_output_length);

/** \brief A function that aborts a previously started secure element cipher
 * operation
 *
 * \param[in,out] op_context    A hardware-specific structure for the
 *                              previously started cipher operation
 */
typedef psa_status_t (*psa_drv_se_cipher_abort_t)(void *op_context);

/** \brief A function that performs the ECB block mode for secure element
 * cipher operations
 *
 * Note: this function should only be used with implementations that do not
 * provide a needed higher-level operation.
 *
 * \param[in,out] drv_context   The driver context structure.
 * \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 \emptydescription
 * \retval #PSA_ERROR_NOT_SUPPORTED \emptydescription
 */
typedef psa_status_t (*psa_drv_se_cipher_ecb_t)(psa_drv_se_context_t *drv_context,
                                                psa_key_slot_number_t key_slot,
                                                psa_algorithm_t algorithm,
                                                psa_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 secure elements.
 *
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup or at build time.
 *
 * If one of the functions is not implemented (such as
 * `psa_drv_se_cipher_ecb_t`), it should be set to NULL.
 */
typedef struct {
    /** The size in bytes of the hardware-specific secure element cipher
     * context structure
     */
    size_t               MBEDTLS_PRIVATE(context_size);
    /** Function that performs a cipher setup operation */
    psa_drv_se_cipher_setup_t  MBEDTLS_PRIVATE(p_setup);
    /** Function that sets a cipher IV (if necessary) */
    psa_drv_se_cipher_set_iv_t MBEDTLS_PRIVATE(p_set_iv);
    /** Function that performs a cipher update operation */
    psa_drv_se_cipher_update_t MBEDTLS_PRIVATE(p_update);
    /** Function that completes a cipher operation */
    psa_drv_se_cipher_finish_t MBEDTLS_PRIVATE(p_finish);
    /** Function that aborts a cipher operation */
    psa_drv_se_cipher_abort_t  MBEDTLS_PRIVATE(p_abort);
    /** Function that performs ECB mode for a cipher operation
     * (Danger: ECB mode should not be used directly by clients of the PSA
     * Crypto Client API)
     */
    psa_drv_se_cipher_ecb_t    MBEDTLS_PRIVATE(p_ecb);
} psa_drv_se_cipher_t;

/**@}*/

/** \defgroup se_asymmetric Secure Element 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
 * keys in a secure element must be done in single function calls.
 */
/**@{*/

/**
 * \brief A function that signs a hash or short message with a private key in
 * a secure element
 *
 * \param[in,out] drv_context       The driver context structure.
 * \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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_asymmetric_sign_t)(psa_drv_se_context_t *drv_context,
                                                     psa_key_slot_number_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 in a secure element
 *
 * \param[in,out] drv_context   The driver context structure.
 * \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 (*psa_drv_se_asymmetric_verify_t)(psa_drv_se_context_t *drv_context,
                                                       psa_key_slot_number_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 in a secure element
 *
 * \param[in,out] drv_context   The driver context structure.
 * \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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_asymmetric_encrypt_t)(psa_drv_se_context_t *drv_context,
                                                        psa_key_slot_number_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 function that decrypts a short message with an asymmetric private
 * key in a secure element.
 *
 * \param[in,out] drv_context   The driver context structure.
 * \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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_asymmetric_decrypt_t)(psa_drv_se_context_t *drv_context,
                                                        psa_key_slot_number_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 secure elements.
 *
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup or at build time.
 *
 * If one of the functions is not implemented, it should be set to NULL.
 */
typedef struct {
    /** Function that performs an asymmetric sign operation */
    psa_drv_se_asymmetric_sign_t    MBEDTLS_PRIVATE(p_sign);
    /** Function that performs an asymmetric verify operation */
    psa_drv_se_asymmetric_verify_t  MBEDTLS_PRIVATE(p_verify);
    /** Function that performs an asymmetric encrypt operation */
    psa_drv_se_asymmetric_encrypt_t MBEDTLS_PRIVATE(p_encrypt);
    /** Function that performs an asymmetric decrypt operation */
    psa_drv_se_asymmetric_decrypt_t MBEDTLS_PRIVATE(p_decrypt);
} psa_drv_se_asymmetric_t;

/**@}*/

/** \defgroup se_aead Secure Element Authenticated Encryption with Additional Data
 * Authenticated Encryption with Additional Data (AEAD) operations with secure
 * elements 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 A function that performs a secure element authenticated encryption
 * operation
 *
 * \param[in,out] drv_context           The driver context structure.
 * \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_drv_se_aead_encrypt_t)(psa_drv_se_context_t *drv_context,
                                                  psa_key_slot_number_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);

/** A function that performs a secure element authenticated decryption operation
 *
 * \param[in,out] drv_context           The driver context structure.
 * \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_drv_se_aead_decrypt_t)(psa_drv_se_context_t *drv_context,
                                                  psa_key_slot_number_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
 * secure element Authenticated Encryption with Additional Data operations
 *
 * 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.
 */
typedef struct {
    /** Function that performs the AEAD encrypt operation */
    psa_drv_se_aead_encrypt_t MBEDTLS_PRIVATE(p_encrypt);
    /** Function that performs the AEAD decrypt operation */
    psa_drv_se_aead_decrypt_t MBEDTLS_PRIVATE(p_decrypt);
} psa_drv_se_aead_t;
/**@}*/

/** \defgroup se_key_management Secure Element 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.
 */
/**@{*/

/** An enumeration indicating how a key is created.
 */
typedef enum {
    PSA_KEY_CREATION_IMPORT, /**< During psa_import_key() */
    PSA_KEY_CREATION_GENERATE, /**< During psa_generate_key() */
    PSA_KEY_CREATION_DERIVE, /**< During psa_key_derivation_output_key() */
    PSA_KEY_CREATION_COPY, /**< During psa_copy_key() */

#ifndef __DOXYGEN_ONLY__
    /** A key is being registered with mbedtls_psa_register_se_key().
     *
     * The core only passes this value to
     * psa_drv_se_key_management_t::p_validate_slot_number, not to
     * psa_drv_se_key_management_t::p_allocate. The call to
     * `p_validate_slot_number` is not followed by any other call to the
     * driver: the key is considered successfully registered if the call to
     * `p_validate_slot_number` succeeds, or if `p_validate_slot_number` is
     * null.
     *
     * With this creation method, the driver must return #PSA_SUCCESS if
     * the given attributes are compatible with the existing key in the slot,
     * and #PSA_ERROR_DOES_NOT_EXIST if the driver can determine that there
     * is no key with the specified slot number.
     *
     * This is an Mbed TLS extension.
     */
    PSA_KEY_CREATION_REGISTER,
#endif
} psa_key_creation_method_t;

/** \brief A function that allocates a slot for a key.
 *
 * To create a key in a specific slot in a secure element, the core
 * first calls this function to determine a valid slot number,
 * then calls a function to create the key material in that slot.
 * In nominal conditions (that is, if no error occurs),
 * the effect of a call to a key creation function in the PSA Cryptography
 * API with a lifetime that places the key in a secure element is the
 * following:
 * -# The core calls psa_drv_se_key_management_t::p_allocate
 *    (or in some implementations
 *    psa_drv_se_key_management_t::p_validate_slot_number). The driver
 *    selects (or validates) a suitable slot number given the key attributes
 *    and the state of the secure element.
 * -# The core calls a key creation function in the driver.
 *
 * The key creation functions in the PSA Cryptography API are:
 * - psa_import_key(), which causes
 *   a call to `p_allocate` with \p method = #PSA_KEY_CREATION_IMPORT
 *   then a call to psa_drv_se_key_management_t::p_import.
 * - psa_generate_key(), which causes
 *   a call to `p_allocate` with \p method = #PSA_KEY_CREATION_GENERATE
 *   then a call to psa_drv_se_key_management_t::p_import.
 * - psa_key_derivation_output_key(), which causes
 *   a call to `p_allocate` with \p method = #PSA_KEY_CREATION_DERIVE
 *   then a call to psa_drv_se_key_derivation_t::p_derive.
 * - psa_copy_key(), which causes
 *   a call to `p_allocate` with \p method = #PSA_KEY_CREATION_COPY
 *   then a call to psa_drv_se_key_management_t::p_export.
 *
 * In case of errors, other behaviors are possible.
 * - If the PSA Cryptography subsystem dies after the first step,
 *   for example because the device has lost power abruptly,
 *   the second step may never happen, or may happen after a reset
 *   and re-initialization. Alternatively, after a reset and
 *   re-initialization, the core may call
 *   psa_drv_se_key_management_t::p_destroy on the slot number that
 *   was allocated (or validated) instead of calling a key creation function.
 * - If an error occurs, the core may call
 *   psa_drv_se_key_management_t::p_destroy on the slot number that
 *   was allocated (or validated) instead of calling a key creation function.
 *
 * Errors and system resets also have an impact on the driver's persistent
 * data. If a reset happens before the overall key creation process is
 * completed (before or after the second step above), it is unspecified
 * whether the persistent data after the reset is identical to what it
 * was before or after the call to `p_allocate` (or `p_validate_slot_number`).
 *
 * \param[in,out] drv_context       The driver context structure.
 * \param[in,out] persistent_data   A pointer to the persistent data
 *                                  that allows writing.
 * \param[in] attributes            Attributes of the key.
 * \param method                    The way in which the key is being created.
 * \param[out] 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.
 *
 * \retval #PSA_SUCCESS
 *         Success.
 *         The core will record \c *key_slot as the key slot where the key
 *         is stored and will update the persistent data in storage.
 * \retval #PSA_ERROR_NOT_SUPPORTED \emptydescription
 * \retval #PSA_ERROR_INSUFFICIENT_STORAGE \emptydescription
 */
typedef psa_status_t (*psa_drv_se_allocate_key_t)(
    psa_drv_se_context_t *drv_context,
    void *persistent_data,
    const psa_key_attributes_t *attributes,
    psa_key_creation_method_t method,
    psa_key_slot_number_t *key_slot);

/** \brief A function that determines whether a slot number is valid
 * for a key.
 *
 * To create a key in a specific slot in a secure element, the core
 * first calls this function to validate the choice of slot number,
 * then calls a function to create the key material in that slot.
 * See the documentation of #psa_drv_se_allocate_key_t for more details.
 *
 * As of the PSA Cryptography API specification version 1.0, there is no way
 * for applications to trigger a call to this function. However some
 * implementations offer the capability to create or declare a key in
 * a specific slot via implementation-specific means, generally for the
 * sake of initial device provisioning or onboarding. Such a mechanism may
 * be added to a future version of the PSA Cryptography API specification.
 *
 * This function may update the driver's persistent data through
 * \p persistent_data. The core will save the updated persistent data at the
 * end of the key creation process. See the description of
 * ::psa_drv_se_allocate_key_t for more information.
 *
 * \param[in,out] drv_context   The driver context structure.
 * \param[in,out] persistent_data   A pointer to the persistent data
 *                                  that allows writing.
 * \param[in] attributes        Attributes of the key.
 * \param method                The way in which the key is being created.
 * \param[in] key_slot          Slot where the key is to be stored.
 *
 * \retval #PSA_SUCCESS
 *         The given slot number is valid for a key with the given
 *         attributes.
 * \retval #PSA_ERROR_INVALID_ARGUMENT
 *         The given slot number is not valid for a key with the
 *         given attributes. This includes the case where the slot
 *         number is not valid at all.
 * \retval #PSA_ERROR_ALREADY_EXISTS
 *         There is already a key with the specified slot number.
 *         Drivers may choose to return this error from the key
 *         creation function instead.
 */
typedef psa_status_t (*psa_drv_se_validate_slot_number_t)(
    psa_drv_se_context_t *drv_context,
    void *persistent_data,
    const psa_key_attributes_t *attributes,
    psa_key_creation_method_t method,
    psa_key_slot_number_t key_slot);

/** \brief A function that imports a key into a secure element 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,out] drv_context   The driver context structure.
 * \param 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] attributes        The key attributes, including the lifetime,
 *                              the key type and the usage policy.
 *                              Drivers should not access the key size stored
 *                              in the attributes: it may not match the
 *                              data passed in \p data.
 *                              Drivers can call psa_get_key_lifetime(),
 *                              psa_get_key_type(),
 *                              psa_get_key_usage_flags() and
 *                              psa_get_key_algorithm() to access this
 *                              information.
 * \param[in] data              Buffer containing the key data.
 * \param[in] data_length       Size of the \p data buffer in bytes.
 * \param[out] bits             On success, the key size in bits. The driver
 *                              must determine this value after parsing the
 *                              key according to the key type.
 *                              This value is not used if the function fails.
 *
 * \retval #PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*psa_drv_se_import_key_t)(
    psa_drv_se_context_t *drv_context,
    psa_key_slot_number_t key_slot,
    const psa_key_attributes_t *attributes,
    const uint8_t *data,
    size_t data_length,
    size_t *bits);

/**
 * \brief A function that destroys a secure element key and restore the slot to
 * its default state
 *
 * This function destroys the content of the key from a secure element.
 * Implementations shall make a best effort to ensure that any previous content
 * of the slot is unrecoverable.
 *
 * This function returns the specified slot to its default state.
 *
 * \param[in,out] drv_context       The driver context structure.
 * \param[in,out] persistent_data   A pointer to the persistent data
 *                                  that allows writing.
 * \param key_slot                  The key slot to erase.
 *
 * \retval #PSA_SUCCESS
 *         The slot's content, if any, has been erased.
 */
typedef psa_status_t (*psa_drv_se_destroy_key_t)(
    psa_drv_se_context_t *drv_context,
    void *persistent_data,
    psa_key_slot_number_t key_slot);

/**
 * \brief A function that exports a secure element 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.
 *
 * This function should generate output in the same format that
 * `psa_export_key()` does. Refer to the
 * documentation of `psa_export_key()` for the format for each key type.
 *
 * \param[in,out] drv_context   The driver context structure.
 * \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 \emptydescription
 * \retval #PSA_ERROR_DOES_NOT_EXIST \emptydescription
 * \retval #PSA_ERROR_NOT_PERMITTED \emptydescription
 * \retval #PSA_ERROR_NOT_SUPPORTED \emptydescription
 * \retval #PSA_ERROR_COMMUNICATION_FAILURE \emptydescription
 * \retval #PSA_ERROR_HARDWARE_FAILURE \emptydescription
 * \retval #PSA_ERROR_CORRUPTION_DETECTED \emptydescription
 */
typedef psa_status_t (*psa_drv_se_export_key_t)(psa_drv_se_context_t *drv_context,
                                                psa_key_slot_number_t key,
                                                uint8_t *p_data,
                                                size_t data_size,
                                                size_t *p_data_length);

/**
 * \brief A function that generates a symmetric or asymmetric key on a secure
 * element
 *
 * If the key type \c type recorded in \p attributes
 * is asymmetric (#PSA_KEY_TYPE_IS_ASYMMETRIC(\c type) = 1),
 * the driver may export the public key at the time of generation,
 * in the format documented for psa_export_public_key() by writing it
 * to the \p pubkey buffer.
 * This is optional, intended for secure elements that output the
 * public key at generation time and that cannot export the public key
 * later. Drivers that do not need this feature should leave
 * \p *pubkey_length set to 0 and should
 * implement the psa_drv_key_management_t::p_export_public function.
 * Some implementations do not support this feature, in which case
 * \p pubkey is \c NULL and \p pubkey_size is 0.
 *
 * \param[in,out] drv_context   The driver context structure.
 * \param 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] attributes        The key attributes, including the lifetime,
 *                              the key type and size, and the usage policy.
 *                              Drivers can call psa_get_key_lifetime(),
 *                              psa_get_key_type(), psa_get_key_bits(),
 *                              psa_get_key_usage_flags() and
 *                              psa_get_key_algorithm() to access this
 *                              information.
 * \param[out] pubkey           A buffer where the driver can write the
 *                              public key, when generating an asymmetric
 *                              key pair.
 *                              This is \c NULL when generating a symmetric
 *                              key or if the core does not support
 *                              exporting the public key at generation time.
 * \param pubkey_size           The size of the `pubkey` buffer in bytes.
 *                              This is 0 when generating a symmetric
 *                              key or if the core does not support
 *                              exporting the public key at generation time.
 * \param[out] pubkey_length    On entry, this is always 0.
 *                              On success, the number of bytes written to
 *                              \p pubkey. If this is 0 or unchanged on return,
 *                              the core will not read the \p pubkey buffer,
 *                              and will instead call the driver's
 *                              psa_drv_key_management_t::p_export_public
 *                              function to export the public key when needed.
 */
typedef psa_status_t (*psa_drv_se_generate_key_t)(
    psa_drv_se_context_t *drv_context,
    psa_key_slot_number_t key_slot,
    const psa_key_attributes_t *attributes,
    uint8_t *pubkey, size_t pubkey_size, size_t *pubkey_length);

/**
 * \brief A struct containing all of the function pointers needed to for secure
 * element key management
 *
 * PSA Crypto API implementations should populate instances of the table as
 * appropriate upon startup or at build time.
 *
 * If one of the functions is not implemented, it should be set to NULL.
 */
typedef struct {
    /** Function that allocates a slot for a key. */
    psa_drv_se_allocate_key_t   MBEDTLS_PRIVATE(p_allocate);
    /** Function that checks the validity of a slot for a key. */
    psa_drv_se_validate_slot_number_t MBEDTLS_PRIVATE(p_validate_slot_number);
    /** Function that performs a key import operation */
    psa_drv_se_import_key_t     MBEDTLS_PRIVATE(p_import);
    /** Function that performs a generation */
    psa_drv_se_generate_key_t   MBEDTLS_PRIVATE(p_generate);
    /** Function that performs a key destroy operation */
    psa_drv_se_destroy_key_t    MBEDTLS_PRIVATE(p_destroy);
    /** Function that performs a key export operation */
    psa_drv_se_export_key_t     MBEDTLS_PRIVATE(p_export);
    /** Function that performs a public key export operation */
    psa_drv_se_export_key_t     MBEDTLS_PRIVATE(p_export_public);
} psa_drv_se_key_management_t;

/**@}*/

/** \defgroup driver_derivation Secure Element 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 Model uses the same functions
 * for both of the flows.
 *
 * There are two different final functions for the flows,
 * `psa_drv_se_key_derivation_derive` and `psa_drv_se_key_derivation_export`.
 * `psa_drv_se_key_derivation_derive` is used when the key material should be
 * placed in a slot on the hardware and not exposed to the caller.
 * `psa_drv_se_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 problematic to manage on embedded platforms, the inputs are passed
 * to the driver via a function, `psa_drv_se_key_derivation_collateral`, that
 * is called multiple times with different `collateral_id`s. Thus, for a key
 * derivation algorithm that required 3 parameter inputs, the flow would look
 * something like:
 * ~~~~~~~~~~~~~{.c}
 * psa_drv_se_key_derivation_setup(kdf_algorithm, source_key, dest_key_size_bytes);
 * psa_drv_se_key_derivation_collateral(kdf_algorithm_collateral_id_0,
 *                                      p_collateral_0,
 *                                      collateral_0_size);
 * psa_drv_se_key_derivation_collateral(kdf_algorithm_collateral_id_1,
 *                                      p_collateral_1,
 *                                      collateral_1_size);
 * psa_drv_se_key_derivation_collateral(kdf_algorithm_collateral_id_2,
 *                                      p_collateral_2,
 *                                      collateral_2_size);
 * psa_drv_se_key_derivation_derive();
 * ~~~~~~~~~~~~~
 *
 * key agreement example:
 * ~~~~~~~~~~~~~{.c}
 * psa_drv_se_key_derivation_setup(alg, source_key. dest_key_size_bytes);
 * psa_drv_se_key_derivation_collateral(DHE_PUBKEY, p_pubkey, pubkey_size);
 * psa_drv_se_key_derivation_export(p_session_key,
 *                                  session_key_size,
 *                                  &session_key_length);
 * ~~~~~~~~~~~~~
 */
/**@{*/

/** \brief A function that Sets up a secure element key derivation operation by
 * specifying the algorithm and the source key sot
 *
 * \param[in,out] drv_context   The driver context structure.
 * \param[in,out] op_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] source_key        The key to be used as the source material for
 *                              the key derivation
 *
 * \retval #PSA_SUCCESS \emptydescription
 */
typedef psa_status_t (*psa_drv_se_key_derivation_setup_t)(psa_drv_se_context_t *drv_context,
                                                          void *op_context,
                                                          psa_algorithm_t kdf_alg,
                                                          psa_key_slot_number_t source_key);

/** \brief A function that provides collateral (parameters) needed for a secure
 * element key derivation or key agreement operation
 *
 * Since many key derivation algorithms require multiple parameters, it is
 * expected that this function may be called multiple times for the same
 * operation, each with a different algorithm-specific `collateral_id`
 *
 * \param[in,out] op_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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_key_derivation_collateral_t)(void *op_context,
                                                               uint32_t collateral_id,
                                                               const uint8_t *p_collateral,
                                                               size_t collateral_size);

/** \brief A function that performs the final secure element key derivation
 * step and place the generated key material in a slot
 *
 * \param[in,out] op_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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_key_derivation_derive_t)(void *op_context,
                                                           psa_key_slot_number_t dest_key);

/** \brief A function that performs the final step of a secure element 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 \emptydescription
 */
typedef psa_status_t (*psa_drv_se_key_derivation_export_t)(void *op_context,
                                                           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 secure
 * element 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.
 */
typedef struct {
    /** The driver-specific size of the key derivation context */
    size_t                           MBEDTLS_PRIVATE(context_size);
    /** Function that performs a key derivation setup */
    psa_drv_se_key_derivation_setup_t      MBEDTLS_PRIVATE(p_setup);
    /** Function that sets key derivation collateral */
    psa_drv_se_key_derivation_collateral_t MBEDTLS_PRIVATE(p_collateral);
    /** Function that performs a final key derivation step */
    psa_drv_se_key_derivation_derive_t     MBEDTLS_PRIVATE(p_derive);
    /** Function that performs a final key derivation or agreement and
     * exports the key */
    psa_drv_se_key_derivation_export_t     MBEDTLS_PRIVATE(p_export);
} psa_drv_se_key_derivation_t;

/**@}*/

/** \defgroup se_registration Secure element driver registration
 */
/**@{*/

/** A structure containing pointers to all the entry points of a
 * secure element driver.
 *
 * Future versions of this specification may add extra substructures at
 * the end of this structure.
 */
typedef struct {
    /** The version of the driver HAL that this driver implements.
     * This is a protection against loading driver binaries built against
     * a different version of this specification.
     * Use #PSA_DRV_SE_HAL_VERSION.
     */
    uint32_t MBEDTLS_PRIVATE(hal_version);

    /** The size of the driver's persistent data in bytes.
     *
     * This can be 0 if the driver does not need persistent data.
     *
     * See the documentation of psa_drv_se_context_t::persistent_data
     * for more information about why and how a driver can use
     * persistent data.
     */
    size_t MBEDTLS_PRIVATE(persistent_data_size);

    /** The driver initialization function.
     *
     * This function is called once during the initialization of the
     * PSA Cryptography subsystem, before any other function of the
     * driver is called. If this function returns a failure status,
     * the driver will be unusable, at least until the next system reset.
     *
     * If this field is \c NULL, it is equivalent to a function that does
     * nothing and returns #PSA_SUCCESS.
     */
    psa_drv_se_init_t MBEDTLS_PRIVATE(p_init);

    const psa_drv_se_key_management_t *MBEDTLS_PRIVATE(key_management);
    const psa_drv_se_mac_t *MBEDTLS_PRIVATE(mac);
    const psa_drv_se_cipher_t *MBEDTLS_PRIVATE(cipher);
    const psa_drv_se_aead_t *MBEDTLS_PRIVATE(aead);
    const psa_drv_se_asymmetric_t *MBEDTLS_PRIVATE(asymmetric);
    const psa_drv_se_key_derivation_t *MBEDTLS_PRIVATE(derivation);
} psa_drv_se_t;

/** The current version of the secure element driver HAL.
 */
/* 0.0.0 patchlevel 5 */
#define PSA_DRV_SE_HAL_VERSION 0x00000005

/** Register an external cryptoprocessor (secure element) driver.
 *
 * This function is only intended to be used by driver code, not by
 * application code. In implementations with separation between the
 * PSA cryptography module and applications, this function should
 * only be available to callers that run in the same memory space as
 * the cryptography module, and should not be exposed to applications
 * running in a different memory space.
 *
 * This function may be called before psa_crypto_init(). It is
 * implementation-defined whether this function may be called
 * after psa_crypto_init().
 *
 * \note Implementations store metadata about keys including the lifetime
 *       value, which contains the driver's location indicator. Therefore,
 *       from one instantiation of the PSA Cryptography
 *       library to the next one, if there is a key in storage with a certain
 *       lifetime value, you must always register the same driver (or an
 *       updated version that communicates with the same secure element)
 *       with the same location value.
 *
 * \param location      The location value through which this driver will
 *                      be exposed to applications.
 *                      This driver will be used for all keys such that
 *                      `location == #PSA_KEY_LIFETIME_GET_LOCATION( lifetime )`.
 *                      The value #PSA_KEY_LOCATION_LOCAL_STORAGE is reserved
 *                      and may not be used for drivers. Implementations
 *                      may reserve other values.
 * \param[in] methods   The method table of the driver. This structure must
 *                      remain valid for as long as the cryptography
 *                      module keeps running. It is typically a global
 *                      constant.
 *
 * \return #PSA_SUCCESS
 *         The driver was successfully registered. Applications can now
 *         use \p location to access keys through the methods passed to
 *         this function.
 * \return #PSA_ERROR_BAD_STATE
 *         This function was called after the initialization of the
 *         cryptography module, and this implementation does not support
 *         driver registration at this stage.
 * \return #PSA_ERROR_ALREADY_EXISTS
 *         There is already a registered driver for this value of \p location.
 * \return #PSA_ERROR_INVALID_ARGUMENT
 *         \p location is a reserved value.
 * \return #PSA_ERROR_NOT_SUPPORTED
 *         `methods->hal_version` is not supported by this implementation.
 * \return #PSA_ERROR_INSUFFICIENT_MEMORY
 * \return #PSA_ERROR_NOT_PERMITTED
 * \return #PSA_ERROR_STORAGE_FAILURE
 * \return #PSA_ERROR_DATA_CORRUPT
 */
psa_status_t psa_register_se_driver(
    psa_key_location_t location,
    const psa_drv_se_t *methods);

/**@}*/

#ifdef __cplusplus
}
#endif

#endif /* PSA_CRYPTO_SE_DRIVER_H */