Secure Element Symmetric Ciphers

Description

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.

Data Structures

struct psa_drv_se_cipher_t
A struct containing all of the function pointers needed to implement cipher operations using secure elements.

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.
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 an secure element cipher operation.
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.
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.
typedef psa_status_t (* psa_drv_se_cipher_abort_t ) (void *op_context)
A function that aborts a previously started secure element 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.

Typedef Documentation

◆ psa_drv_se_cipher_setup_t

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.

Parameters
[in,out] drv_context The driver context structure.
[in,out] op_context A structure that will contain the hardware-specific cipher context.
[in] key_slot The slot of the key to be used for the operation
[in] algorithm The algorithm to be used in the cipher operation
[in] direction Indicates whether the operation is an encrypt or decrypt
Return values
PSA_SUCCESS
PSA_ERROR_NOT_SUPPORTED

◆ psa_drv_se_cipher_set_iv_t

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 an 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.

Parameters
[in,out] op_context A structure that contains the previously set up hardware-specific cipher context
[in] p_iv A buffer containing the initialization vector
[in] iv_length The size (in bytes) of the p_iv buffer
Return values
PSA_SUCCESS

◆ psa_drv_se_cipher_update_t

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.

Parameters
[in,out] op_context A hardware-specific structure for the previously started cipher operation
[in] p_input A buffer containing the data to be encrypted/decrypted
[in] input_size The size in bytes of the buffer pointed to by p_input
[out] p_output The caller-allocated buffer where the output will be placed
[in] output_size The allocated size in bytes of the p_output buffer
[out] p_output_length After completion, will contain the number of bytes placed in the p_output buffer
Return values
PSA_SUCCESS

◆ psa_drv_se_cipher_finish_t

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.

Parameters
[in,out] op_context A hardware-specific structure for the previously started cipher operation
[out] p_output The caller-allocated buffer where the output will be placed
[in] output_size The allocated size in bytes of the p_output buffer
[out] p_output_length After completion, will contain the number of bytes placed in the p_output buffer
Return values
PSA_SUCCESS

◆ psa_drv_se_cipher_abort_t

typedef psa_status_t (* psa_drv_se_cipher_abort_t) (void *op_context)

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

Parameters
[in,out] op_context A hardware-specific structure for the previously started cipher operation

◆ psa_drv_se_cipher_ecb_t

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.

Parameters
[in,out] drv_context The driver context structure.
[in] key_slot The slot of the key to be used for the operation
[in] algorithm The algorithm to be used in the cipher operation
[in] direction Indicates whether the operation is an encrypt or decrypt
[in] p_input A buffer containing the data to be encrypted/decrypted
[in] input_size The size in bytes of the buffer pointed to by p_input
[out] p_output The caller-allocated buffer where the output will be placed
[in] output_size The allocated size in bytes of the p_output buffer
Return values
PSA_SUCCESS
PSA_ERROR_NOT_SUPPORTED