/**
* \brief AES interrupt handler
*
* \note AES interrupt subroutine in CBC decryption mode.
*
*/
static void aes_isr_cbc_decrypt_handler(void)
{
/* When CBC is used the answer must be xored with the previous cipher text
* or the initialization vector to reconstruct the plaintext. */
/* Set AES decryption of a single block in manual mode. */
aes_configure(AES_DECRYPT, AES_MANUAL, AES_XOR_ON);
if(byte_count == 0) {
aes_write_inputdata(init);
}else {
aes_write_inputdata((cipher_block_ans + byte_count -
BLOCK_LENGTH));
}
aes_read_outputdata((plain_block_ans + byte_count));
byte_count += BLOCK_LENGTH;
if(byte_count >= BLOCK_LENGTH * BLOCK_COUNT) {
int_end = true;
}else {
aes_configure(AES_DECRYPT, AES_AUTO, AES_XOR_OFF);
/* Load key into AES key memory. */
aes_set_key(lastsubkey);
/* Load data into AES state memory. */
aes_write_inputdata((cipher_block_ans + byte_count));
// NOTE: since we're in auto mode, the ciphering process will start as
// soon as the correct number of input data is written. In this case,
// the process should start when we write the sixteenth byte.
}
}
/**
* \brief Test AES decryption function.
*
* This test decrypts the pre-encrypted data and checks
* whether it is correct.
*
* \param test Current test case.
*/
static void run_aes_decryption_test(const struct test_case *test)
{
t_key decrypted_data;
bool success;
set_buffer(decrypted_data, 0x00);
set_buffer(lastsubkey, 0x00);
/* Call helper function to generate a last subkey for decryption */
if (!aes_lastsubkey_generate(encryption_key, lastsubkey)) {
success = false;
test_assert_true(test, !success,
"Could not generate last subkey");
} else {
/* Configure module for manual decryption */
aes_software_reset();
aes_set_key(lastsubkey);
aes_configure(AES_DECRYPT, AES_MANUAL, AES_XOR_OFF);
aes_write_inputdata(pre_encrypted_data);
aes_start();
do {
/* Wait until AES is finished or an error occurs. */
} while (aes_is_busy());
aes_read_outputdata(decrypted_data);
/* Verify that the decrypted data is correct */
success = compare_data_block(decrypted_data, encryption_data);
test_assert_true(test, success,
"Decrypted values do not match excepted values");
}
}
/**
* \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 Run encryption, then decryption. Announce end by interrupt.
*
* This test encrypts a data block, decrypts it, and checks if it's
* correct with respect to the input data block. Utilizes interrupts
* to let the software know when a encryption/decryption is done.
* AUTO mode will be used in this test.
*
* \param test Current test case.
*/
static void run_aes_encrypt_and_decrypt_test(const struct test_case *test)
{
bool success = true;
set_buffer(output_data, 0x00);
set_buffer(lastsubkey, 0x00);
aes_software_reset();
/* Configure AES for automatic mode, with XOR, and interrupt. */
aes_configure(AES_ENCRYPT, AES_AUTO, AES_XOR_ON);
aes_isr_configure(AES_INTLVL_LO);
aes_set_key(encryption_key);
aes_write_inputdata(encryption_data);
/*
* Wait for it to end, since we actually don't have
* anything better to do
*/
while (!aes_is_finished) {
/* Intentionally left empty */
}
/* output_data should now contain encrypted data */
/* Configure AES for automatic mode, XOR off. Last subkey
* is already in the module, so we don't need to load it
*/
aes_is_finished = false;
aes_configure(AES_DECRYPT, AES_AUTO, AES_XOR_OFF);
aes_write_inputdata(output_data);
while (!aes_is_finished) {
/* Intentionally left empty */
}
/* The AES module should be finished now, and output_data
* should contain our initial data. */
success = compare_data_block(output_data, encryption_data);
test_assert_true(test, success,
"End values do not match start values");
}
/**
* \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 AES interrupt handler
*
* \note AES interrupt subroutine in CBC encryption mode.
*
*/
static void aes_isr_cbc_encrypt_handler(void)
{
aes_read_outputdata((cipher_block_ans + byte_count));
byte_count += BLOCK_LENGTH;
if(byte_count >= BLOCK_LENGTH * BLOCK_COUNT) {
int_end = true;
}else {
/* Load key into AES key memory. */
aes_set_key(key);
/* Load data into AES state memory. */
aes_write_inputdata((data_block + byte_count));
// NOTE: since we're in auto mode, the ciphering process will start as
// soon as the correct number of input data is written. In this case,
// the process should start when we write the sixteenth byte.
}
}
/**
* \brief Test AES encryption function
*
* This test generates an encrypted byte string from a key and input,
* and compares it to a pre-encrypted value.
*
* \param test Current test case.
*/
static void run_aes_encryption_test(const struct test_case *test)
{
t_data encrypted_data;
bool success;
/* Zero out the output data storage */
set_buffer(encrypted_data, 0x00);
/* Reset the module */
aes_software_reset();
/*
* Configure AES module to encrypt, triggered by software,
* with no XOR
*/
aes_configure(AES_ENCRYPT, AES_MANUAL, AES_XOR_OFF);
aes_set_key(encryption_key);
aes_write_inputdata(encryption_data);
aes_start();
do {
/* Wait until AES is finished or an error occurs. */
} while (aes_is_busy());
aes_read_outputdata(encrypted_data);
/* Verify that this data is correct by comparing it
* to our pre-encrypted value
*/
success = compare_data_block(encrypted_data, pre_encrypted_data);
test_assert_true(test, success,
"Encrypted values do not match pre-encrypted"
" values");
}
int main( void )
{
uint8_t i;
board_init();
sysclk_init();
sleepmgr_init();
/* Assume that everything is ok */
success = true;
/* Enable the AES clock. */
sysclk_enable_module(SYSCLK_PORT_GEN, SYSCLK_AES);
/* Do AES encryption and decryption of a single block. */
//********************************************************
// CIPHER IN MANUAL MODE:
// - 128bit cryptographic key and data
// - ECB cipher mode
// - XOR disable
// - Polling AES State Ready Interrupt flag
//********************************************************
/* 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);
/* Disable the AES interrupt. */
aes_isr_configure(AES_INTLVL_OFF);
/* Load key into AES key memory. */
aes_set_key(key);
/* Load data into AES state memory. */
aes_write_inputdata(plain_text);
/* Start encryption. */
aes_start();
do {
/* Wait until AES is finished or an error occurs. */
} while (aes_is_busy());
/* Store the result if not error. */
if (!aes_is_error()) {
aes_read_outputdata(single_ans);
} else {
success = false;
}
/* Check if encrypted answer is equal to cipher result. */
for (i = 0; i < BLOCK_LENGTH ; i++ ) {
if (cipher_text[i] != single_ans[i]) {
success = false;
}
}
//********************************************************
// DECIPHER IN AUTO MODE:
// - 128bit cryptographic key and data
// - ECB cipher mode
// - XOR disable
// - Polling AES State Ready Interrupt flag
//********************************************************
/* Generate last subkey. */
if (!aes_lastsubkey_generate(key, lastsubkey)) {
success = false;
}
/* 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 decryption of a single block in auto mode. */
aes_configure(AES_DECRYPT, AES_AUTO, AES_XOR_OFF);
/* Disable the AES interrupt. */
aes_isr_configure(AES_INTLVL_OFF);
/* Load key into AES key memory. */
aes_set_key(lastsubkey);
/* Load data into AES state memory. */
aes_write_inputdata(cipher_text);
// NOTE: since we're in auto mode, the ciphering process will start as soon
// as the correct number of input data is written. In this case, the
// process should start when we write the sixteenth byte.
do {
/* Wait until AES is finished or an error occurs. */
} while (aes_is_busy());
/* Store the result if not error. */
if (!aes_is_error()) {
aes_read_outputdata(single_ans);
} else {
success = false;
}
/* Check if decrypted answer is equal to plaintext. */
for (i = 0; i < BLOCK_LENGTH ; i++ ) {
if (plain_text[i] != single_ans[i]) {
success = false;
}
}
/* Disable the AES clock. */
sysclk_disable_module(SYSCLK_PORT_GEN, SYSCLK_AES);
/* Indicate final result by lighting LED. */
if (success) {
/* If the example ends up here every thing is ok. */
ioport_set_pin_low(LED0_GPIO);
} else {
/* If the example ends up here something is wrong. */
ioport_set_pin_low(LED1_GPIO);
}
while (true) {
/* Go to sleep. */
sleepmgr_enter_sleep();
}
}
int main( void )
{
uint16_t i;
/* Enable all three interrupt levels of the PMIC. */
pmic_init();
board_init();
sysclk_init();
sleepmgr_init();
/* Assume that everything is ok*/
success = true;
/* Enable the AES clock. */
sysclk_enable_module(SYSCLK_PORT_GEN, SYSCLK_AES);
/* Do AES decryption of a single block with AES interrupt handler. */
//********************************************************
// DECIPHER IN MANUAL MODE:
// - 128bit cryptographic key and data
// - ECB cipher mode
// - XOR disable
// - Interrupt call back handler
//********************************************************
/* Generate last subkey. */
if (!aes_lastsubkey_generate(key, lastsubkey)) {
success = false;
}
/* Enable global interrupts. */
cpu_irq_enable();
/* Assume no interrupt is finished. */
int_end = false;
byte_count = 0;
/* Set AES interrupt call back function. */
aes_set_callback(&aes_isr_handler);
/* 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_DECRYPT, AES_MANUAL, AES_XOR_OFF);
/* Enable the AES low level interrupt. */
aes_isr_configure(AES_INTLVL_LO);
/* Load key into AES key memory. */
aes_set_key(lastsubkey);
/* Load data into AES state memory. */
aes_write_inputdata(cipher_text);
/* Start encryption. */
aes_start();
do{
/* Wait until the AES interrupt is finished. */
} while (!int_end);
/* Do AES encryption and decryption of multi blocks. */
//********************************************************
// CIPHER IN AUTO MODE:
// - 128bit cryptographic key and data
// - CBC cipher mode
// - XOR on
// - Interrupt call back handler
//********************************************************
/* Assume no interrupt is finished. */
int_end = false;
byte_count = 0;
/* Set AES interrupt call back function. */
aes_set_callback(&aes_isr_cbc_encrypt_handler);
/* 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();
/* Load initial vector into AES state memory. */
aes_write_inputdata(init);
/* Set AES encryption of a single block in auto mode. */
aes_configure(AES_ENCRYPT, AES_AUTO, AES_XOR_ON);
/* Enable the AES low level interrupt. */
aes_isr_configure(AES_INTLVL_LO);
/* Load key into AES key memory. */
aes_set_key(key);
/* Load data into AES state memory. */
aes_write_inputdata(data_block);
// NOTE: since we're in auto mode, the ciphering process will start as soon
// as the correct number of input data is written. In this case, the
// process should start when we write the sixteenth byte.
do{
/* Wait until the AES interrupt is finished. */
} while (!int_end);
//********************************************************
// DECIPHER IN AUTO MODE:
// - 128bit cryptographic key and data
// - CBC cipher mode
// - XOR off
// - Interrupt call back handler
//********************************************************
/* Generate last subkey. */
if (!aes_lastsubkey_generate(key, lastsubkey)) {
success = false;
}
/* Assume no interrupt is finished. */
int_end = false;
byte_count = 0;
/* Set AES interrupt call back function. */
aes_set_callback(&aes_isr_cbc_decrypt_handler);
/* 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 decryption of a single block in auto mode. */
aes_configure(AES_DECRYPT, AES_AUTO, AES_XOR_OFF);
/* Enable the AES low level interrupt. */
aes_isr_configure(AES_INTLVL_LO);
/* Load key into AES key memory. */
aes_set_key(lastsubkey);
/* Load data into AES state memory. */
aes_write_inputdata(cipher_block_ans);
// NOTE: since we're in auto mode, the ciphering process will start as soon
// as the correct number of input data is written. In this case, the
// process should start when we write the sixteenth byte.
do{
/* Wait until the AES interrupt is finished. */
} while (!int_end);
/* Check if decrypted answer is equal to plaintext. */
for (i = 0; i < BLOCK_LENGTH * BLOCK_COUNT ; i++) {
if (data_block[i] != plain_block_ans[i]){
success = false;
}
}
/* Disable the AES clock. */
sysclk_disable_module(SYSCLK_PORT_GEN, SYSCLK_AES);
/* Indicate final result by lighting LED. */
if (success) {
/* If the example ends up here every thing is ok. */
ioport_set_pin_low(LED0_GPIO);
} else {
/* If the example ends up here something is wrong. */
ioport_set_pin_low(LED1_GPIO);
}
while (true) {
/* Go to sleep. */
sleepmgr_enter_sleep();
}
}
