Group se_cipher

group se_cipher

Encryption and Decryption using secure element keys in block modes other than ECB must be done in multiple parts, using the following flow:

psa_drv_se_cipher_setup_t
psa_drv_se_cipher_set_iv_t (optional depending upon block mode)
psa_drv_se_cipher_update_t
psa_drv_se_cipher_update_t
…
psa_drv_se_cipher_finish_t

If a previously started secure element Cipher operation needs to be terminated, it should be done so by the psa_drv_se_cipher_abort_t. Failure to do so may result in allocated resources not being freed or in other undefined behavior.

In situations where a PSA Cryptographic API implementation is using a block mode not-supported by the underlying hardware or driver, it can construct the block mode itself, while calling the psa_drv_se_cipher_ecb_t function for the cipher operations.

Typedefs

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

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.