File crypto_se_driver.h

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.

Defines

PSA_DRV_SE_HAL_VERSION

The current version of the secure element driver HAL.

Typedefs

typedef psa_status_t (*psa_drv_se_init_t)(psa_drv_se_context_t *drv_context, void *persistent_data, psa_key_location_t location)

A driver initialization function.

Param drv_context:

[inout] The driver context structure.

Param persistent_data:

[inout] 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_mac_setup_t)(psa_drv_se_context_t *drv_context, void *op_context, psa_key_slot_number_t key_slot, psa_algorithm_t algorithm)

A function that starts a secure element MAC operation for a PSA Crypto Driver implementation.

Param drv_context:

[inout] The driver context structure.

Param op_context:

[inout] A structure that will contain the hardware-specific MAC context

Param key_slot:

[in] The slot of the key to be used for the operation

Param algorithm:

[in] The algorithm to be used to underly the MAC operation

Retval PSA_SUCCESS:

Success.

typedef psa_status_t (*psa_drv_se_mac_update_t)(void *op_context, const uint8_t *p_input, size_t input_length)

A function that continues a previously started secure element MAC operation.

Param op_context:

[inout] A hardware-specific structure for the previously-established MAC operation to be updated

Param p_input:

[in] A buffer containing the message to be appended to the MAC operation

Param input_length:

[in] The size in bytes of the input message buffer

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)

a function that completes a previously started secure element MAC operation by returning the resulting MAC.

Param op_context:

[inout] A hardware-specific structure for the previously started MAC operation to be finished

Param p_mac:

[out] A buffer where the generated MAC will be placed

Param mac_size:

[in] The size in bytes of the buffer that has been allocated for the output buffer

Param p_mac_length:

[out] 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_verify_t)(void *op_context, const uint8_t *p_mac, size_t mac_length)

A function that completes a previously started secure element MAC operation by comparing the resulting MAC against a provided value.

Param op_context:

[inout] A hardware-specific structure for the previously started MAC operation to be finished

Param p_mac:

[in] The MAC value against which the resulting MAC will be compared against

Param mac_length:

[in] 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_abort_t)(void *op_context)

A function that aborts a previous started secure element MAC operation.

Param op_context:

[inout] A hardware-specific structure for the previously started MAC operation to be aborted

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)

A function that performs a secure element MAC operation in one command and returns the calculated MAC.

Param drv_context:

[inout] The driver context structure.

Param p_input:

[in] A buffer containing the message to be MACed

Param input_length:

[in] The size in bytes of p_input

Param key_slot:

[in] The slot of the key to be used

Param alg:

[in] The algorithm to be used to underlie the MAC operation

Param p_mac:

[out] A buffer where the generated MAC will be placed

Param mac_size:

[in] The size in bytes of the p_mac buffer

Param p_mac_length:

[out] 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_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)

A function that performs a secure element MAC operation in one command and compares the resulting MAC against a provided value.

Param drv_context:

[inout] The driver context structure.

Param p_input:

[in] A buffer containing the message to be MACed

Param input_length:

[in] The size in bytes of input

Param key_slot:

[in] The slot of the key to be used

Param alg:

[in] The algorithm to be used to underlie the MAC operation

Param p_mac:

[in] The MAC value against which the resulting MAC will be compared against

Param mac_length:

[in] 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_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)

A function that provides the cipher setup function for a secure element driver.

Param drv_context:

[inout] The driver context structure.

Param op_context:

[inout] A structure that will contain the hardware-specific cipher context.

Param key_slot:

[in] The slot of the key to be used for the operation

Param algorithm:

[in] The algorithm to be used in the cipher operation

Param direction:

[in] Indicates whether the operation is an encrypt or decrypt

Retval PSA_SUCCESS:

Retval PSA_ERROR_NOT_SUPPORTED:

typedef psa_status_t (*psa_drv_se_cipher_set_iv_t)(void *op_context, const uint8_t *p_iv, size_t iv_length)

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 op_context:

[inout] A structure that contains the previously set up hardware-specific cipher context

Param p_iv:

[in] A buffer containing the initialization vector

Param iv_length:

[in] The size (in bytes) of the p_iv buffer

Retval PSA_SUCCESS:

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)

A function that continues a previously started secure element cipher operation.

Param op_context:

[inout] A hardware-specific structure for the previously started cipher operation

Param p_input:

[in] A buffer containing the data to be encrypted/decrypted

Param input_size:

[in] The size in bytes of the buffer pointed to by p_input

Param p_output:

[out] The caller-allocated buffer where the output will be placed

Param output_size:

[in] The allocated size in bytes of the p_output buffer

Param p_output_length:

[out] After completion, will contain the number of bytes placed in the p_output buffer

Retval PSA_SUCCESS:

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)

A function that completes a previously started secure element cipher operation.

Param op_context:

[inout] A hardware-specific structure for the previously started cipher operation

Param p_output:

[out] The caller-allocated buffer where the output will be placed

Param output_size:

[in] The allocated size in bytes of the p_output buffer

Param p_output_length:

[out] After completion, will contain the number of bytes placed in the p_output buffer

Retval PSA_SUCCESS:

typedef psa_status_t (*psa_drv_se_cipher_abort_t)(void *op_context)

A function that aborts a previously started secure element cipher operation.

Param op_context:

[inout] A hardware-specific structure for the previously started cipher operation

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)

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 drv_context:

[inout] The driver context structure.

Param key_slot:

[in] The slot of the key to be used for the operation

Param algorithm:

[in] The algorithm to be used in the cipher operation

Param direction:

[in] Indicates whether the operation is an encrypt or decrypt

Param p_input:

[in] A buffer containing the data to be encrypted/decrypted

Param input_size:

[in] The size in bytes of the buffer pointed to by p_input

Param p_output:

[out] The caller-allocated buffer where the output will be placed

Param output_size:

[in] The allocated size in bytes of the p_output buffer

Retval PSA_SUCCESS:

Retval PSA_ERROR_NOT_SUPPORTED:

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)

A function that signs a hash or short message with a private key in a secure element.

Param drv_context:

[inout] The driver context structure.

Param key_slot:

[in] Key slot of an asymmetric key pair

Param alg:

[in] A signature algorithm that is compatible with the type of key

Param p_hash:

[in] The hash to sign

Param hash_length:

[in] Size of the p_hash buffer in bytes

Param p_signature:

[out] Buffer where the signature is to be written

Param signature_size:

[in] Size of the p_signature buffer in bytes

Param p_signature_length:

[out] On success, the number of bytes that make up the returned signature value

Retval PSA_SUCCESS:

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)

A function that verifies the signature a hash or short message using an asymmetric public key in a secure element.

Param drv_context:

[inout] The driver context structure.

Param key_slot:

[in] Key slot of a public key or an asymmetric key pair

Param alg:

[in] A signature algorithm that is compatible with the type of key

Param p_hash:

[in] The hash whose signature is to be verified

Param hash_length:

[in] Size of the p_hash buffer in bytes

Param p_signature:

[in] Buffer containing the signature to verify

Param signature_length:

[in] Size of the p_signature buffer in bytes

Retval PSA_SUCCESS:

The signature is valid.

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)

A function that encrypts a short message with an asymmetric public key in a secure element.

Param drv_context:

[inout] The driver context structure.

Param key_slot:

[in] Key slot of a public key or an asymmetric key pair

Param alg:

[in] An asymmetric encryption algorithm that is compatible with the type of key

Param p_input:

[in] The message to encrypt

Param input_length:

[in] Size of the p_input buffer in bytes

Param p_salt:

[in] 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:

[in] Size of the p_salt buffer in bytes If p_salt is NULL, pass 0.

Param p_output:

[out] Buffer where the encrypted message is to be written

Param output_size:

[in] Size of the p_output buffer in bytes

Param p_output_length:

[out] On success, the number of bytes that make up the returned output

Retval PSA_SUCCESS:

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)

A function that decrypts a short message with an asymmetric private key in a secure element.

Param drv_context:

[inout] The driver context structure.

Param key_slot:

[in] Key slot of an asymmetric key pair

Param alg:

[in] An asymmetric encryption algorithm that is compatible with the type of key

Param p_input:

[in] The message to decrypt

Param input_length:

[in] Size of the p_input buffer in bytes

Param p_salt:

[in] 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:

[in] Size of the p_salt buffer in bytes If p_salt is NULL, pass 0.

Param p_output:

[out] Buffer where the decrypted message is to be written

Param output_size:

[in] Size of the p_output buffer in bytes

Param p_output_length:

[out] On success, the number of bytes that make up the returned output

Retval PSA_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 encryption operation.

Param drv_context:

[inout] The driver context structure.

Param key_slot:

[in] Slot containing the key to use.

Param algorithm:

[in] The AEAD algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true)

Param p_nonce:

[in] Nonce or IV to use

Param nonce_length:

[in] Size of the p_nonce buffer in bytes

Param p_additional_data:

[in] Additional data that will be authenticated but not encrypted

Param additional_data_length:

[in] Size of p_additional_data in bytes

Param p_plaintext:

[in] Data that will be authenticated and encrypted

Param plaintext_length:

[in] Size of p_plaintext in bytes

Param p_ciphertext:

[out] 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:

[in] Size of the p_ciphertext buffer in bytes

Param p_ciphertext_length:

[out] On success, the size of the output in the p_ciphertext 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)

A function that performs a secure element authenticated decryption operation

Param drv_context:

[inout] The driver context structure.

Param key_slot:

[in] Slot containing the key to use

Param algorithm:

[in] The AEAD algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true)

Param p_nonce:

[in] Nonce or IV to use

Param nonce_length:

[in] Size of the p_nonce buffer in bytes

Param p_additional_data:

[in] Additional data that has been authenticated but not encrypted

Param additional_data_length:

[in] Size of p_additional_data in bytes

Param p_ciphertext:

[in] 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:

[in] Size of p_ciphertext in bytes

Param p_plaintext:

[out] Output buffer for the decrypted data

Param plaintext_size:

[in] Size of the p_plaintext buffer in bytes

Param p_plaintext_length:

[out] On success, the size of the output in the p_plaintext buffer

Retval PSA_SUCCESS:

Success.

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)

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:

  1. 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.

  2. The core calls a key creation function in the driver.

The key creation functions in the PSA Cryptography API are:

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 drv_context:

[inout] The driver context structure.

Param persistent_data:

[inout] A pointer to the persistent data that allows writing.

Param attributes:

[in] Attributes of the key.

Param method:

The way in which the key is being created.

Param key_slot:

[out] 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 *key_slot as the key slot where the key is stored and will update the persistent data in storage.

Retval PSA_ERROR_NOT_SUPPORTED:

Retval PSA_ERROR_INSUFFICIENT_STORAGE:

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)

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 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 drv_context:

[inout] The driver context structure.

Param persistent_data:

[inout] A pointer to the persistent data that allows writing.

Param attributes:

[in] Attributes of the key.

Param method:

The way in which the key is being created.

Param key_slot:

[in] 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_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)

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 drv_context:

[inout] 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 attributes:

[in] 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 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 data:

[in] Buffer containing the key data.

Param data_length:

[in] Size of the data buffer in bytes.

Param bits:

[out] 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_destroy_key_t)(psa_drv_se_context_t *drv_context, void *persistent_data, psa_key_slot_number_t key_slot)

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 drv_context:

[inout] The driver context structure.

Param persistent_data:

[inout] 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_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)

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 drv_context:

[inout] The driver context structure.

Param key:

[in] Slot whose content is to be exported. This must be an occupied key slot.

Param p_data:

[out] Buffer where the key data is to be written.

Param data_size:

[in] Size of the p_data buffer in bytes.

Param p_data_length:

[out] On success, the number of bytes that make up the key data.

Retval PSA_SUCCESS:

Retval PSA_ERROR_DOES_NOT_EXIST:

Retval PSA_ERROR_NOT_PERMITTED:

Retval PSA_ERROR_NOT_SUPPORTED:

Retval PSA_ERROR_COMMUNICATION_FAILURE:

Retval PSA_ERROR_HARDWARE_FAILURE:

Retval PSA_ERROR_CORRUPTION_DETECTED:

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)

A function that generates a symmetric or asymmetric key on a secure element.

If the key type type recorded in attributes is asymmetric (PSA_KEY_TYPE_IS_ASYMMETRIC(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 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 *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 pubkey is NULL and pubkey_size is 0.

Param drv_context:

[inout] 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 attributes:

[in] 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 pubkey:

[out] A buffer where the driver can write the public key, when generating an asymmetric key pair. This is 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 pubkey_length:

[out] On entry, this is always 0. On success, the number of bytes written to pubkey. If this is 0 or unchanged on return, the core will not read the 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_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)

A function that Sets up a secure element key derivation operation by specifying the algorithm and the source key sot.

Param drv_context:

[inout] The driver context structure.

Param op_context:

[inout] A hardware-specific structure containing any context information for the implementation

Param kdf_alg:

[in] The algorithm to be used for the key derivation

Param source_key:

[in] The key to be used as the source material for the key derivation

Retval PSA_SUCCESS:

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)

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 op_context:

[inout] A hardware-specific structure containing any context information for the implementation

Param collateral_id:

[in] An ID for the collateral being provided

Param p_collateral:

[in] A buffer containing the collateral data

Param collateral_size:

[in] The size in bytes of the collateral

Retval PSA_SUCCESS:

typedef psa_status_t (*psa_drv_se_key_derivation_derive_t)(void *op_context, psa_key_slot_number_t dest_key)

A function that performs the final secure element key derivation step and place the generated key material in a slot.

Param op_context:

[inout] A hardware-specific structure containing any context information for the implementation

Param dest_key:

[in] The slot where the generated key material should be placed

Retval PSA_SUCCESS:

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)

A function that performs the final step of a secure element key agreement and place the generated key material in a buffer.

Param p_output:

[out] Buffer in which to place the generated key material

Param output_size:

[in] The size in bytes of p_output

Param p_output_length:

[out] Upon success, contains the number of bytes of key material placed in p_output

Retval PSA_SUCCESS:

Enums

enum psa_key_creation_method_t

An enumeration indicating how a key is created.

Values:

enumerator PSA_KEY_CREATION_IMPORT

During psa_import_key()

enumerator PSA_KEY_CREATION_GENERATE

During psa_generate_key()

enumerator PSA_KEY_CREATION_DERIVE

During psa_key_derivation_output_key()

enumerator PSA_KEY_CREATION_COPY

During psa_copy_key()

enumerator PSA_KEY_CREATION_REGISTER

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.

Functions

psa_status_t psa_register_se_driver(psa_key_location_t location, const psa_drv_se_t *methods)

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.

Parameters:

  • 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.

  • methods – [in] 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.

Returns:

PSA_SUCCESS The driver was successfully registered. Applications can now use location to access keys through the methods passed to this function.

Returns:

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.

Returns:

PSA_ERROR_ALREADY_EXISTS There is already a registered driver for this value of location.

Returns:

PSA_ERROR_INVALID_ARGUMENT location is a reserved value.

Returns:

PSA_ERROR_NOT_SUPPORTED methods->hal_version is not supported by this implementation.

Returns:

PSA_ERROR_INSUFFICIENT_MEMORY

Returns:

PSA_ERROR_NOT_PERMITTED

Returns:

PSA_ERROR_STORAGE_FAILURE

Returns:

PSA_ERROR_DATA_CORRUPT

struct psa_drv_se_context_t
#include <crypto_se_driver.h>

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.

Public Members

const void *const private_persistent_data

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 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 size_t private_persistent_data_size

The size of 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.

uintptr_t private_transient_data

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.

struct psa_drv_se_mac_t
#include <crypto_se_driver.h>

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).

Public Members

size_t private_context_size

The size in bytes of the hardware-specific secure element MAC context structure

psa_drv_se_mac_setup_t private_p_setup

Function that performs a MAC setup operation

psa_drv_se_mac_update_t private_p_update

Function that performs a MAC update operation

psa_drv_se_mac_finish_t private_p_finish

Function that completes a MAC operation

psa_drv_se_mac_finish_verify_t private_p_finish_verify

Function that completes a MAC operation with a verify check

psa_drv_se_mac_abort_t private_p_abort

Function that aborts a previously started MAC operation

psa_drv_se_mac_generate_t private_p_mac

Function that performs a MAC operation in one call

psa_drv_se_mac_verify_t private_p_mac_verify

Function that performs a MAC and verify operation in one call

struct psa_drv_se_cipher_t
#include <crypto_se_driver.h>

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.

Public Members

size_t private_context_size

The size in bytes of the hardware-specific secure element cipher context structure

psa_drv_se_cipher_setup_t private_p_setup

Function that performs a cipher setup operation

psa_drv_se_cipher_set_iv_t private_p_set_iv

Function that sets a cipher IV (if necessary)

psa_drv_se_cipher_update_t private_p_update

Function that performs a cipher update operation

psa_drv_se_cipher_finish_t private_p_finish

Function that completes a cipher operation

psa_drv_se_cipher_abort_t private_p_abort

Function that aborts a cipher operation

psa_drv_se_cipher_ecb_t private_p_ecb

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)

struct psa_drv_se_asymmetric_t
#include <crypto_se_driver.h>

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.

Public Members

psa_drv_se_asymmetric_sign_t private_p_sign

Function that performs an asymmetric sign operation

psa_drv_se_asymmetric_verify_t private_p_verify

Function that performs an asymmetric verify operation

psa_drv_se_asymmetric_encrypt_t private_p_encrypt

Function that performs an asymmetric encrypt operation

psa_drv_se_asymmetric_decrypt_t private_p_decrypt

Function that performs an asymmetric decrypt operation

struct psa_drv_se_aead_t
#include <crypto_se_driver.h>

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.

Public Members

psa_drv_se_aead_encrypt_t private_p_encrypt

Function that performs the AEAD encrypt operation

psa_drv_se_aead_decrypt_t private_p_decrypt

Function that performs the AEAD decrypt operation

struct psa_drv_se_key_management_t
#include <crypto_se_driver.h>

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.

Public Members

psa_drv_se_allocate_key_t private_p_allocate

Function that allocates a slot for a key.

psa_drv_se_validate_slot_number_t private_p_validate_slot_number

Function that checks the validity of a slot for a key.

psa_drv_se_import_key_t private_p_import

Function that performs a key import operation

psa_drv_se_generate_key_t private_p_generate

Function that performs a generation

psa_drv_se_destroy_key_t private_p_destroy

Function that performs a key destroy operation

psa_drv_se_export_key_t private_p_export

Function that performs a key export operation

psa_drv_se_export_key_t private_p_export_public

Function that performs a public key export operation

struct psa_drv_se_key_derivation_t
#include <crypto_se_driver.h>

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.

Public Members

size_t private_context_size

The driver-specific size of the key derivation context

psa_drv_se_key_derivation_setup_t private_p_setup

Function that performs a key derivation setup

psa_drv_se_key_derivation_collateral_t private_p_collateral

Function that sets key derivation collateral

psa_drv_se_key_derivation_derive_t private_p_derive

Function that performs a final key derivation step

psa_drv_se_key_derivation_export_t private_p_export

Function that performs a final key derivation or agreement and exports the key

struct psa_drv_se_t
#include <crypto_se_driver.h>

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.

Public Members

uint32_t private_hal_version

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.

size_t private_persistent_data_size

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.

psa_drv_se_init_t private_p_init

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 NULL, it is equivalent to a function that does nothing and returns PSA_SUCCESS.

const psa_drv_se_key_management_t *private_key_management
const psa_drv_se_mac_t *private_mac
const psa_drv_se_cipher_t *private_cipher
const psa_drv_se_aead_t *private_aead
const psa_drv_se_asymmetric_t *private_asymmetric
const psa_drv_se_key_derivation_t *private_derivation