include/psa/crypto_driver.h

#ifndef __PSA_CRYPTO_DRIVER_H__
#define __PSA_CRYPTO_DRIVER_H__

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

typedef uint32_t psa_status_t;
typedef uint32_t psa_algorithm_t;
typedef uint32_t encrypt_or_decrypt_t;
typedef uint32_t psa_key_slot_t;
typedef uint32_t psa_key_type_t;

/** \defgroup opaque_mac Opaque Message Authentication Code
 * @{
 */
/** \brief A function that starts an MAC operation for a PSA Crypto Driver implementation using an opaque key
 * 
 * \param p_context     A structure that will contain the hardware-specific MAC context
 * \param key_slot      The slot of the key to be used for the operation
 * \param 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 p_context     A hardware-specific structure for the previously-established MAC operation to be continued
 * \param p_input       A buffer containing the message to be appended to the MAC operation
 * \param input_length  The size in bytes of the input message buffer
 */
typedef psa_status_t (*pcd_mac_opaque_update_t)( void *p_context,
                                                 const unsigned char *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 p_context         A hardware-specific structure for the previously started MAC operation to be fiinished
 * \param p_output          A buffer where the generated MAC will be placed
 * \param output_size       The size in bytes of the buffer that has been allocated for the `output` buffer
 * \param p_output_length   After completion, the address will contain the number of bytes placed in the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_opaque_finish_t)( void *p_ctx,
                                                 unsigned char *p_output,
                                                 size_t output_size,
                                                 size_t *p_output_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 p_context     A hardware-specific structure for the previously started MAC operation to be fiinished
 * \param p_mac         The MAC value against which the resulting MAC will be compared against
 * \param mac_length    The size in bytes of the value stored in `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 unsigned char *p_mac,
                                                        size_t mac_length );

/** \brief A funciton that performs an MAC operation in one command and return the calculated MAC using an opaque key
 * 
 * \param p_input           A buffer containing the message to be MACed
 * \param input_length      The size in bytes of `input`
 * \param key_slot          The slot of the key to be used
 * \param alg               The algorithm to be used to underlie the MAC operation
 * \param p_output          A buffer where the generated MAC will be placed
 * \param output_size       The size in bytes of the `output` buffer
 * \param p_output_length   After completion, the address will contain the number of bytes placed in the `output` buffer
 * 
 * \retval PSA_SUCCESS
 *         Success.
 */
typedef psa_status_t (*pcd_mac_opaque_t)( const unsigned char *p_input,
                                         size_t input_length,
                                         psa_key_slot_t key_slot,
                                         psa_algorithm_t alg,
                                         unsigned char *p_output,
                                         size_t output_size,
                                         size_t *p_output_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 p_input       A buffer containing the message to be MACed
 * \param input_length  The size in bytes of `input`
 * \param key_slot      The slot of the key to be used
 * \param alg           The algorithm to be used to underlie the MAC operation
 * \param p_mac         The MAC value against which the resulting MAC will be compared against
 * \param 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 unsigned char *p_input,
                                                size_t input_length,
                                                psa_key_slot_t key_slot,
                                                psa_algorithm_t alg,
                                                const unsigned char *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_t`), it should be set to NULL.
 * 
 */
struct pcd_mac_opaque_t {
    size_t                   context_size;  /**<The size in bytes of the hardware-specific Opaque-MAC Context structure */
    pcd_mac_opaque_setup_t  *p_setup;       /**< Function that performs the setup operation */
    pcd_mac_opaque_update_t *p_update;      /**< Function that performs the update operation */
    pcd_mac_opaque_finish_t *p_finish;      /**< Function that completes the operation */
    pcd_mac_opaque_t        *p_mac;         /**< Function that performs the MAC operation in one call */
    pcd_mac_opaque_verify_t *p_mac_verify;  /**<Function that performs the MAC and verify operation in one call */
};
/** @} */

/** \defgroup transparent_mac Transparent Message Authentication Code
 * @{
 */

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

/** \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>_start
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying hash function, and `MAC_VARIANT` is the specific variant of a 
 * MAC operation (such as HMAC or CMAC)
 * 
 * \param p_context     A structure that will contain the hardware-specific MAC context
 * \param p_key         A buffer containing the cleartext key material to be used in the operation
 * \param key_length    The size in bytes of the key material
 * 
 * \retval  PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_transparent_start_t)( struct pcd_mac_transparent_context_t *p_context,
                                                     const unsigned char *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 p_context     A hardware-specific structure for the previously-established MAC operation to be continued
 * \param p_input       A buffer containing the message to be appended to the MAC operation
 * \param input_length  The size in bytes of the input message buffer
 */
typedef psa_status_t (*pcd_mac_transparent_update_t)( struct pcd_mac_transparent_context_t *p_context,
                                                      const unsigned char *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 p_context         A hardware-specific structure for the previously started MAC operation to be fiinished
 * \param p_output          A buffer where the generated MAC will be placed
 * \param output_size       The size in bytes of the buffer that has been allocated for the `p_output` buffer
 * \param p_output_length   After completion, will contain the number of bytes placed in the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_mac_transparent_finish_t)( struct pcd_mac_transparent_context_t *p_context,
                                                     unsigned char *p_output,
                                                     size_t output_size,
                                                     size_t *p_output_length );

/** @}
 */

/** \defgroup opaque_cipher Opaque Symmetric Ciphers
 ** @{
 */

/** \brief A function pointer that provides the cipher setup function for opaque-key operations
 *
 * TBD: Since this is an opaque API (External, in Gilles nomeclature), shouldn't we be receiving a key handle/slot instead of key data? This is how I
 * will write it

 * \param p_context     A structure that will contain the hardware-specific cipher context.
 * \param key_slot      THe slot of the key to be used for the operation
 * \param algorithm     The algorithm to be used in the cipher operation
 * \param 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
 * 
 * Note that the psa_cipher_* function set 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 it's RNG features
 * 
 * \param p_context A structure that contains the previously set up hardware-specific cipher context
 * \param p_iv      A buffer containing the initialization vector
 * \param 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 p_context         A hardware-specific structure for the previously started cipher operation
 * \param p_input           A buffer containing the data to be encrypted/decrypted
 * \param input_size        The size in bytes of the buffer pointed to by `p_input`
 * \param p_output          The caller-allocated buffer where the output will be placed
 * \param output_size       The allocated size in bytes of the `p_output` buffer
 * \param 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 p_context         A hardware-specific structure for the previously started cipher operation
 * \param p_output          The caller-callocated buffer where the output will be placed
 * \param output_size       The allocated size in bytes of the `p_output` buffer
 * \param 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 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 key_slot      The slot of the key to be used for the operation
 * \param algorithm     The algorithm to be used in the cipher operation
 * \param direction     Indicates whether the operation is an encrypt or decrypt
 * \param p_input       A buffer containing the data to be encrypted/decrypted
 * \param input_size    The size in bytes of the buffer pointed to by `p_input`
 * \param p_output      The caller-allocated byffer where the output will be placed
 * \param 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 {
    size_t                      size;       /**<The size in bytes of the hardware-specific Opaque Cipher context structure */
    pcd_cipher_opaque_setup_t  *p_setup;    /**< Function that performs the setup operation */
    pcd_cipher_opaque_set_iv_t *p_set_iv;   /**< Function that sets the IV (if necessary) */
    pcd_cipher_opaque_update_t *p_update;   /**< Function that performs the update operation */
    pcd_cipher_opaque_finish_t *p_finish;   /**< Function that completes the operation */
    pcd_cipher_opaque_ecb_t    *p_ecb;      /**< Function that performs ECB mode for the cipher (Danger: ECB mode is insecure) */
};

/** @}
 */

/** \defgroup transparent_cipher Transparent Block Cipher
 * @{
 */

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

/** \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 convention:
 * ~~~~~~~~~~~~~{.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)
 * 
 * \param p_context         A structure that will contain the hardware-specific cipher context
 * \param direction         Indicates if the operation is an encrypt or a decrypt
 * \param p_key_data        A buffer containing the cleartext key material to be used in the operation
 * \param key_data_size     The size in bytes of the key material
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_transparent_setup_t) ( struct 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 p_context     A structure that contains the previously setup hardware-specific cipher context
 * \param p_iv          A buffer containing the initialization vecotr
 * \param 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) ( struct 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)
 * 
 * TODO: Should the PSA Crypto API implementation calling these functions handle padding? What about hardware that handles padding?
 * 
 * \param p_context         A hardware-specific structure for the previously started cipher operation
 * \param p_input           A buffer containing the data to be encrypted or decrypted
 * \param input_size        The size in bytes of the `p_input` buffer
 * \param p_output          A caller-allocated buffer where the generated output will be placed
 * \param output_size       The size in bytes of the `p_output` buffer
 * \param 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) ( struct 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)
 * 
 * TODO: Should the PSA Crypto API implementation calling these functions handle padding? What about hardware that handles padding?
 * 
 * \param p_context         A hardware-specific structure for the previously started cipher operation
 * \param p_output          A caller-allocated buffer where the generated output will be placed
 * \param output_size       The size in bytes of the `p_output` buffer
 * \param 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) ( struct 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)
 * 
 * TODO: Should the PSA Crypto API implementation calling these functions handle padding? What about hardware that handles padding?
 * 
 * \param p_context         A hardware-specific structure for the previously started cipher operation
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_cipher_transparent_abort_t) ( struct pcd_cipher_transparent_context_t *p_context );

/** @}
 */

/** \defgroup digest Message Digests
 * @{
 */

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

/** \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>_start
 * ~~~~~~~~~~~~~
 * Where `ALGO` is the name of the underlying hash function
 * 
 * \param p_context     A structure that will contain the hardware-specific hash context
 * 
 * \retval  PSA_SUCCESS     Success.
 */
typedef psa_status_t (*pcd_hash_start_t)(struct 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 p_context     A hardware-specific structure for the previously-established hash operation to be continued
 * \param p_input       A buffer containing the message to be appended to the hash operation
 * \param input_length  The size in bytes of the input message buffer
 */
typedef psa_status_t (*pcd_hash_update_t)(struct pcd_hash_context_t *p_context, const unsigned char *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 p_context         A hardware-specific structure for the previously started hash operation to be fiinished
 * \param p_output          A buffer where the generated digest will be placed
 * \param output_size       The size in bytes of the buffer that has been allocated for the `p_output` buffer
 * 
 * \retval PSA_SUCCESS
 *          Success.
 */
typedef psa_status_t (*pcd_hash_finish_t)(struct pcd_hash_context_t *p_context, unsigned char *p_output, size_t output_size);

/** \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 p_context     A hardware-specific structure for the previously started hash operation to be aborted
 */
typedef void (*pcd_hash_abort_t)(struct pcd_hash_context_t *p_context);

/** @}
 */


/** \defgroup opaque_asymmetric Opaque Asymmetric Cryptography
 * @{
 */

/**
 * \brief A function that signs a hash or short message with a private key.
 *
 * \param key_slot                  Key slot of an asymmetric key pair.
 * \param alg                       A signature algorithm that is compatible with
 *                                  the type of `key`.
 * \param[in] p_hash                The hash or message to sign.
 * \param hash_length               Size of the `p_hash` buffer in bytes.
 * \param[out] p_signature          Buffer where the signature is to be written.
 * \param 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 a public key.
 *
  * \param key_slot         Key slot of a public key or an asymmetric key pair.
 * \param 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 hash_length       Size of the `p_hash` buffer in bytes.
 * \param[in] p_signature   Buffer containing the signature to verify.
 * \param 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 a public key.
 *
 * \param key_slot              Key slot of a public key or an asymmetric key pair.
 * \param alg                   An asymmetric encryption algorithm that is
 *                              compatible with the type of `key`.
 * \param[in] p_input           The message to encrypt.
 * \param 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 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 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 a private key.
 *
 * \param key_slot              Key slot of an asymmetric key pair.
 * \param alg                   An asymmetric encryption algorithm that is
 *                              compatible with the type of \p key.
 * \param[in] p_input           The message to decrypt.
 * \param 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 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 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 {
    pcd_asymmetric_opaque_sign_t    *p_sign;    /**< Function that performs the asymmetric sign operation */
    pcd_asymmetric_opaque_verify_t  *p_verify;  /**< Function that performs the asymmetric verify operation */
    pcd_asymmetric_opaque_encrypt_t *p_encrypt; /**< Function that performs the asymmetric encrypt operation */
    pcd_asymmetric_opaque_decrypt_t *p_decrypt; /**< Function that performs the asymmetric decrypt operation */
};

/** @}
 */

/** \defgroup transparent_asymmetric Transparent Asymmetric Cryptography
 * @{
 */


/**
 * \brief A function that signs a hash or short message with a transparent 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 p_key                     A buffer containing the private key material.
 * \param key_size                  The size in bytes of the `p_key` data
 * \param alg                       A signature algorithm that is compatible with
 *                                  the type of `p_key`.
 * \param[in] p_hash                The hash or message to sign.
 * \param hash_length               Size of the `p_hash` buffer in bytes.
 * \param[out] p_signature          Buffer where the signature is to be written.
 * \param 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 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 p_key             A buffer containing the public key material.
 * \param key_size          The size in bytes of the `p_key` data
 * \param 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 hash_length       Size of the `p_hash` buffer in bytes.
 * \param[in] p_signature   Buffer containing the signature to verify.
 * \param 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 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 p_key                 A buffer containing the public key material
 * \param key_size              The size in bytes of the `p_key` data
 * \param alg                   An asymmetric encryption algorithm that is
 *                              compatible with the type of `key`.
 * \param[in] p_input           The message to encrypt.
 * \param 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 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 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 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 p_key                 A buffer containing the private key material
 * \param key_size              The size in bytes of the `p_key` data
 * \param alg                   An asymmetric encryption algorithm that is
 *                              compatible with the type of \p key.
 * \param[in] p_input           The message to decrypt.
 * \param 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 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 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
 * * @{
 */

/** Process an authenticated encryption operation using an opaque key.
 *
 * \param key_slot                  Slot containing the key to use.
 * \param algorithm                 The AEAD algorithm to compute
 *                                  (\c PSA_ALG_XXX value such that
 *                                  #PSA_ALG_IS_AEAD(\p alg) is true).
 * \param[in] p_nonce               Nonce or IV to use.
 * \param 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 additional_data_length    Size of `p_additional_data` in bytes.
 * \param[in] p_plaintext           Data that will be authenticated and
 *                                  encrypted.
 * \param 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 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 key_slot                  Slot containing the key to use.
 * \param algorithm                 The AEAD algorithm to compute
 *                                  (\c PSA_ALG_XXX value such that
 *                                  #PSA_ALG_IS_AEAD(\p alg) is true).
 * \param[in] p_nonce               Nonce or IV to use.
 * \param 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 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 ciphertext_length         Size of `p_ciphertext` in bytes.
 * \param[out] p_plaintext          Output buffer for the decrypted data.
 * \param 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 {
    psa_aead_opaque_encrypt_t *p_encrypt;   /**< Function that performs the AEAD encrypt operation */
    psa_aead_opaque_decrypt_t *p_decrypt;   /**< Function that performs the AEAD decrypt operation */
};
/** @} 
 */

/** \defgroup aead_transparent AEAD Transparent
 */

/** Process an authenticated encryption operation.
 * 
 * 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 p_key                   A pointer to the key material
 * \param key_length              The size in bytes of the key material
 * \param alg                     The AEAD algorithm to compute
 *                                (\c PSA_ALG_XXX value such that
 *                                #PSA_ALG_IS_AEAD(\p alg) is true).
 * \param[in] nonce               Nonce or IV to use.
 * \param nonce_length            Size of the \p nonce buffer in bytes.
 * \param[in] additional_data     Additional data that will be MACed
 *                                but not encrypted.
 * \param additional_data_length  Size of \p additional_data in bytes.
 * \param[in] plaintext           Data that will be MACed and
 *                                encrypted.
 * \param plaintext_length        Size of \p 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 ciphertext_size         Size of the \p ciphertext buffer in bytes.
 *                                This must be at least
 *                                #PSA_AEAD_ENCRYPT_OUTPUT_SIZE(\p alg,
 *                                \p plaintext_length).
 * \param[out] ciphertext_length  On success, the size of the output
 *                                in the \b 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.
 * 
 * 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 p_key                   A pointer to the key material
 * \param key_length              The size in bytes of the key material
 * \param alg                     The AEAD algorithm to compute
 *                                (\c PSA_ALG_XXX value such that
 *                                #PSA_ALG_IS_AEAD(\p alg) is true).
 * \param[in] nonce               Nonce or IV to use.
 * \param nonce_length            Size of the \p nonce buffer in bytes.
 * \param[in] additional_data     Additional data that has been MACed
 *                                but not encrypted.
 * \param additional_data_length  Size of \p 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 ciphertext_length       Size of \p ciphertext in bytes.
 * \param[out] plaintext          Output buffer for the decrypted data.
 * \param plaintext_size          Size of the \p plaintext buffer in bytes.
 *                                This must be at least
 *                                #PSA_AEAD_DECRYPT_OUTPUT_SIZE(\p alg,
 *                                \p 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 rng Entropy Generation
 * @{
 */

/** \brief A hardware-specific structure for a entropy providing hardware
 */
struct pcd_entropy_context_t {
    // Implementation specific
};

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

/** \brief Get a specified number of bytes from the entropy source
 * 
 * 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 p_context                 A hardware-specific structure containing any context information for the implementation
 * \param p_buffer                  A caller-allocated buffer for the retrieved bytes to be placed in
 * \param buffer_size               The allocated size of `p_buffer`
 * \param 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)( struct 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 {
    pcd_entropy_init_t *p_init;            /**< Function that performs initialization for the entropy source */
    pcd_entropy_get_bytes_t *p_get_bytes;  /**< Function that performs the get_bytes operation for the entropy source */
};
/** @}
 */

/** \defgroup key_management Key Management
 * @{
 */

/** \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 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 type          Key type (a \c PSA_KEY_TYPE_XXX value).
 * \param[in] p_data    Buffer containing the key data.
 * \param data_length   Size of the \p 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,
                                                  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 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 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 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 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 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
 */
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 {
    pcd_opaque_import_key_t *p_import;          /**< Function that performs the key import operation */
    pcd_destroy_key_t       *p_destroy;         /**< Function that performs the key destroy operation */
    pcd_export_key_t        *p_export;          /**< Function that performs the key export operation */
    pcd_export_public_key_t *p_export_public;   /**< Function that perforsm the public key export operation */
};

/** @}
 */

/** \defgroup 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 Set up a key derivation operation by specifying the algorithm and the source key sot
 * 
 * \param kdf_alg       The algorithm to be used for the key derivation
 * \param 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 )( 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 collateral_id
 * \param p_collateral
 * \param collateral_size
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t (*pcd_key_derivation_collateral_t ) ( uint32_t collateral_id, const uint8_t p_collateral, uint32_t collateral_size );

/** \brief Perform the final key derivation step and place the generated key material in a slot
 * 
 * param dest_key       The slot where the generated key material should be placed
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t ( *pcd_key_derivation_derive_t )( psa_key_slot_t dest_key );

/** \brief Pefform the final step of a key agreement and place the generated key material in a buffer
 * 
 * \param p_output
 * \param output_size
 * \param p_output_length
 * 
 * \retval PSA_SUCCESS
 */
typedef psa_status_t ( *pcd_key_derivation_export_t )( uint8_t *p_output, uint32_t output_size, uint32_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 {
    pcd_key_derivation_setup_t      *p_setup;       /**< Function that performs the key derivation setup */
    pcd_key_derivation_collateral_t *p_collateral;  /**< Function that sets the key derivation collateral */
    pcd_key_derivation_derive_t     *p_derive;      /**< Function that performs the final key derivation step */
    pcd_key_derivation_export_t     *p_export;      /**< Function that perforsm the final key derivation or agreement and exports the key */
};

/** @}
 */

#endif // __PSA_CRYPTO_DRIVER_H__