Hi,
I was trying to decrypt an encrypted message I send form my phone using the psa/crypto library. I managed to send the encrypted message over to my board by ble correctly, however when I tried to decrypt the message, I was meet with an error (status -135). I was unable to find any information with regards to this error code. The picture below explains my issue:
As seen from the image, I am able to send the encrypted data from my phone correctly to the board but I am unable decrypt it. I am quite sure I have implemented the decryption process correctly as I did not run into the error log I have set for debugging until the decryption process. Below is the segment of the code I wrote for the decryption:
static size_t received_data_len = 0;
static void bt_receive_cb(struct bt_conn *conn, const uint8_t *const data, uint16_t len)
{
int err;
char addr[BT_ADDR_LE_STR_LEN] = { 0 };
bt_addr_le_to_str(bt_conn_get_dst(conn), addr, ARRAY_SIZE(addr));
LOG_INF("Received data from: %s", addr);
// Assuming the received data is encrypted using AES-CCM
uint8_t nonce[12] = { 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B};
uint8_t aad[8] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
uint8_t plaintext[CONFIG_BT_NUS_UART_BUFFER_SIZE] = { 0 };
size_t plaintext_len = sizeof(plaintext);
psa_status_t status;
// Initialize the PSA crypto API
status = psa_crypto_init();
if (status != PSA_SUCCESS) {
LOG_ERR("Failed to initialize PSA crypto API");
return;
}
// Import the AES key into the PSA keystore
psa_key_attributes_t key_attributes = PSA_KEY_ATTRIBUTES_INIT;
psa_set_key_type(&key_attributes, PSA_KEY_TYPE_AES);
psa_set_key_bits(&key_attributes, 128);
psa_set_key_usage_flags(&key_attributes, PSA_KEY_USAGE_DECRYPT);
psa_set_key_algorithm(&key_attributes, PSA_ALG_CCM);
psa_key_id_t key_id;
uint8_t aes_key[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10 };
status = psa_import_key(&key_attributes, aes_key, sizeof(aes_key), &key_id);
if (status != PSA_SUCCESS) {
LOG_ERR("Failed to import AES key");
return;
}
// Decrypt the received data using AES-CCM
status = psa_aead_decrypt(key_id, PSA_ALG_CCM, nonce, sizeof(nonce),
aad, sizeof(aad),
data, sizeof(data),
plaintext, sizeof(plaintext),
&plaintext_len);
LOG_INF("Decryption in progress......");
if (status == PSA_SUCCESS) {
LOG_INF("Decryption successful");
LOG_INF("Decrypted plaintext (hex): ");
for (size_t i = 0; i < plaintext_len; i++) {
LOG_INF("%02X", plaintext[i]);
}
// Process the decrypted plaintext data
// ...
} else {
LOG_ERR("Decryption failed (status %d)", status);
}
if ((received_data_len + len) <= sizeof(received_data)) {
memcpy(&received_data[received_data_len], data, len);
received_data_len += len;
// Log the received data
LOG_INF("Received data (hex):");
for (size_t i = 0; i < received_data_len; i++) {
LOG_INF("0x%02X", received_data[i]);
}
} else {
LOG_ERR("Received data exceeds the buffer size");
}
for (uint16_t pos = 0; pos != len;) {
struct uart_data_t *tx = k_malloc(sizeof(*tx));
if (!tx) {
LOG_WRN("Not able to allocate UART send data buffer");
return;
}
/* Keep the last byte of TX buffer for potential LF char. */
size_t tx_data_size = sizeof(tx->data) - 1;
if ((len - pos) > tx_data_size) {
tx->len = tx_data_size;
} else {
tx->len = (len - pos);
}
memcpy(tx->data, &data[pos], tx->len);
pos += tx->len;
/* Append the LF character when the CR character triggered
* transmission from the peer.
*/
if ((pos == len) && (data[len - 1] == '\r')) {
tx->data[tx->len] = '\n';
tx->len++;
}
/* STEP 8.3 - Forward the data received over Bluetooth LE to the UART peripheral */
err = uart_tx(uart, tx->data, tx->len, SYS_FOREVER_MS);
if (err) {
k_fifo_put(&fifo_uart_tx_data, tx);
}
}
}
This is how I formuate my key, aad and nonce in flutter, i make sure to check that its the same as in the code for the board:
final key = KeyParameter(Uint8List.fromList([0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10]));
final nonce = Uint8List.fromList([0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B]);
final aad = Uint8List.fromList([0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07]);
final nonce = Uint8List.fromList([0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B]);
final aad = Uint8List.fromList([0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07]);
I was wondering if you have any idea as to what is causing this error?
Thanks and regards,
Johan
