/**
* \brief Generate AES sub key
*
* Get AES sub key by encryption of dummy data.
*
* \param key Pointer to AES key input.
* \param last_sub_key Pointer to AES sub key output.
*
*/
static bool aes_lastsubkey_generate(t_key key, t_key last_sub_key)
{
bool keygen_ok;
aes_software_reset();
/* Set AES encryption of a single block in manual mode. */
aes_configure(AES_ENCRYPT, AES_MANUAL, AES_XOR_OFF);
/* Load key into AES key memory. */
aes_set_key(key);
/* Load dummy data into AES state memory. It isn't important what is
* written, just that a write cycle occurs. */
aes_write_inputdata(dummy_data);
/* Start encryption. */
aes_start();
do {
/* Wait until AES is finished or an error occurs. */
} while (aes_is_busy());
/* If not error. */
if (!aes_is_error()) {
/* Store the last subkey. */
aes_get_key(last_sub_key);
aes_clear_interrupt_flag();
keygen_ok = true;
} else {
aes_clear_error_flag();
keygen_ok = false;
}
return keygen_ok;
}
/**
* \brief Test AES state interface functions
*
* This test verifies that the functions used to check the state of the module
* are working, and that the clear functions work correctly.
*
* \param test Current test case
*/
static void run_aes_state_interface_test(const struct test_case *test)
{
/* We first reset the module */
aes_software_reset();
/* The module should not be busy or in error */
test_assert_true(test, aes_is_busy(), "Module should not be busy!");
test_assert_true(test, !aes_is_error(), "Module should not be in error!");
/* Get the module into error by trying to start the module before loading
* values into state memory */
aes_start();
/* Module should now be in error */
test_assert_true(test, aes_is_error(), "Module should be in error!");
/* Clear the flag and check that it has been cleared */
aes_clear_error_flag();
test_assert_true(test, !aes_is_error(),
"Module error flag should have been cleared!");
/* Load up dummy data into the module and do a cycle, then check that
* the aes_is_busy() function actually works */
aes_software_reset();
aes_configure(AES_ENCRYPT, AES_MANUAL, AES_XOR_OFF);
aes_set_key(encryption_key);
aes_write_inputdata(dummy_data);
aes_start();
/* Check that the module is busy, the module uses more CPU cycles to
* complete than it takes to see if it is busy */
test_assert_true(test, aes_is_busy(), "AES module should be busy!");
do {
/* Wait until the module is finished */
} while(aes_is_busy());
/* The module now has data in the status register. We want to clear the
* flag without reading the data. First verify that the flag is set */
test_assert_true(test, AES.STATUS & AES_SRIF_bm,
"State ready interrupt flag is not set!");
aes_clear_interrupt_flag();
/* Now, check that we have cleared the flag */
test_assert_true(test, !(AES.STATUS & AES_SRIF_bm),
"State ready interrupt flag should not be set!");
}
/**
* \brief Generate AES sub key
*
* \note Get AES sub key by encryption of dummy data.
*
* \param key Pointer to AES key input.
* \param last_sub_key Pointer to AES sub key output.
*
*/
static bool aes_lastsubkey_generate(t_key key, t_key last_sub_key)
{
bool keygen_ok;
uint8_t i;
/* Before using the AES it is recommended to do an AES software reset to
* put the module in known state, in case other parts of your code has
* accessed the AES module. */
aes_software_reset();
/* Set AES encryption of a single block in manual mode. */
aes_configure(AES_ENCRYPT, AES_MANUAL, AES_XOR_OFF);
/* Load key into AES key memory. */
aes_set_key(key);
/* Load dummy data into AES state memory. */
for (i = 0; i < BLOCK_LENGTH; i++) {
AES.STATE = 0x00;
}
/* Start encryption. */
aes_start();
do {
/* Wait until AES is finished or an error occurs. */
} while (aes_is_busy());
/* If not error. */
if (!aes_is_error()) {
/* Store the last subkey. */
aes_get_key(last_sub_key);
aes_clear_interrupt_flag();
keygen_ok = true;
} else {
aes_clear_error_flag();
keygen_ok = false;
}
return keygen_ok;
}
