Quick Start Guide for AES - Callback

The supported board list:

• SAM L21 Xplained Pro
• SAM L22 Xplained Pro

This example demonstrates how to use the AES driver to perform:

• ECB encryption and decryption
• CBC encryption and decryption
• CFB128 encryption and decryption
• OFB encryption and decryption
• CTR encryption and decryption

Upon startup, the program uses the USART driver to display application output message from which several encryption/decryption modes can be tested.

Quick Start Callback

Prerequisites

There are no prerequisites for this use case.

Code

Add to the main application source file, outside of any functions:

#define AES_EXAMPLE_REFBUF_SIZE 4

/* @{ */
uint32_t ref_plain_text[AES_EXAMPLE_REFBUF_SIZE] = {
    0xe2bec16b,
    0x969f402e,
    0x117e3de9,
    0x2a179373
};

uint32_t ref_cipher_text_ecb[AES_EXAMPLE_REFBUF_SIZE] = {
    0xb47bd73a,
    0x60367a0d,
    0xf3ca9ea8,
    0x97ef6624
};

uint32_t ref_cipher_text_cbc[AES_EXAMPLE_REFBUF_SIZE] = {
    0xacab4976,
    0x46b21981,
    0x9b8ee9ce,
    0x7d19e912
};

uint32_t ref_cipher_text_cfb128[AES_EXAMPLE_REFBUF_SIZE] = {
    0x2ed93f3b,
    0x20ad2db7,
    0xf8493433,
    0x4afb3ce8
};

uint32_t ref_cipher_text_ofb[AES_EXAMPLE_REFBUF_SIZE] = {
    0x2ed93f3b,
    0x20ad2db7,
    0xf8493433,
    0x4afb3ce8
};

uint32_t ref_cipher_text_ctr[AES_EXAMPLE_REFBUF_SIZE] = {
    0x91614d87,
    0x26e320b6,
    0x6468ef1b,
    0xceb60d99
};

const uint32_t key128[4] = {
    0x16157e2b,
    0xa6d2ae28,
    0x8815f7ab,
    0x3c4fcf09
};

const uint32_t init_vector[4] = {
    0x03020100,
    0x07060504,
    0x0b0a0908,
    0x0f0e0d0c
};

const uint32_t init_vector_ctr[4] = {
    0xf3f2f1f0,
    0xf7f6f5f4,
    0xfbfaf9f8,
    0xfffefdfc
};

/* @} */

Add to the main application source file, outside of any functions:

/* Output data array */
static uint32_t output_data[AES_EXAMPLE_REFBUF_SIZE];
/* State indicate */
volatile bool state = false;

struct aes_config g_aes_cfg;
struct aes_module aes_instance;
struct usart_module usart_instance;

Copy-paste the following setup code to your user application:

static void configure_usart(void)
{

    struct usart_config config_usart;
    usart_get_config_defaults(&config_usart);
    config_usart.baudrate    = 38400;
    config_usart.mux_setting = EDBG_CDC_SERCOM_MUX_SETTING;
    config_usart.pinmux_pad0 = EDBG_CDC_SERCOM_PINMUX_PAD0;
    config_usart.pinmux_pad1 = EDBG_CDC_SERCOM_PINMUX_PAD1;
    config_usart.pinmux_pad2 = EDBG_CDC_SERCOM_PINMUX_PAD2;
    config_usart.pinmux_pad3 = EDBG_CDC_SERCOM_PINMUX_PAD3;
    stdio_serial_init(&usart_instance, EDBG_CDC_MODULE, &config_usart);
    usart_enable(&usart_instance);
}


static void aes_callback(void)
{
    /* Read the output. */
    aes_read_output_data(&aes_instance, output_data);
    state = true;
}

static void ecb_mode_test(void)
{
    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- ECB cipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_ENCRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_AUTO_START;
    g_aes_cfg.opmode = AES_ECB_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);
    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* The initialization vector is not used by the ECB cipher mode. */

    aes_set_new_message(&aes_instance);
    /* Write the data to be ciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_plain_text);
    aes_clear_new_message(&aes_instance);

    /* Wait for the end of the encryption process. */
    while (false == state) {
    }

    if ((ref_cipher_text_ecb[0] != output_data[0]) ||
            (ref_cipher_text_ecb[1] != output_data[1]) ||
            (ref_cipher_text_ecb[2] != output_data[2]) ||
            (ref_cipher_text_ecb[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }

    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- ECB decipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_DECRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_AUTO_START;
    g_aes_cfg.opmode = AES_ECB_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* The initialization vector is not used by the ECB cipher mode. */
    aes_set_new_message(&aes_instance);
    /* Write the data to be deciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_cipher_text_ecb);
    aes_clear_new_message(&aes_instance);
    /* Wait for the end of the decryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_plain_text[0] != output_data[0]) ||
            (ref_plain_text[1] != output_data[1]) ||
            (ref_plain_text[2] != output_data[2]) ||
            (ref_plain_text[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }
}

static void cbc_mode_test(void)
{
    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- CBC cipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_ENCRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_MANUAL_START;
    g_aes_cfg.opmode = AES_CBC_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector);

    /* Write the data to be ciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_plain_text);
    aes_set_new_message(&aes_instance);
    aes_start(&aes_instance);
    aes_clear_new_message(&aes_instance);
    /* Wait for the end of the encryption process. */
    while (false == state) {
    }

    if ((ref_cipher_text_cbc[0] != output_data[0]) ||
            (ref_cipher_text_cbc[1] != output_data[1]) ||
            (ref_cipher_text_cbc[2] != output_data[2]) ||
            (ref_cipher_text_cbc[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }

    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- CBC decipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_DECRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_AUTO_START;
    g_aes_cfg.opmode = AES_CBC_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector);

    aes_set_new_message(&aes_instance);
    /* Write the data to be deciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_cipher_text_cbc);
    aes_clear_new_message(&aes_instance);

    /* Wait for the end of the decryption process. */
    while (false == state) {
    }

    if ((ref_plain_text[0] != output_data[0]) ||
            (ref_plain_text[1] != output_data[1]) ||
            (ref_plain_text[2] != output_data[2]) ||
            (ref_plain_text[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }
}

static void cfb128_mode_test(void)
{
    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- CFB128 cipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_ENCRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_MANUAL_START;
    g_aes_cfg.opmode = AES_CFB_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector);

    /* Write the data to be ciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_plain_text);
    aes_set_new_message(&aes_instance);
    aes_start(&aes_instance);
    aes_clear_new_message(&aes_instance);
    /* Wait for the end of the encryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_cipher_text_cfb128[0] != output_data[0]) ||
            (ref_cipher_text_cfb128[1] != output_data[1]) ||
            (ref_cipher_text_cfb128[2] != output_data[2]) ||
            (ref_cipher_text_cfb128[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }

    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- CFB128 decipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_DECRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_MANUAL_START;
    g_aes_cfg.opmode = AES_CFB_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector);

    /* Write the data to be deciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_cipher_text_cfb128);
    aes_set_new_message(&aes_instance);
    aes_start(&aes_instance);
    aes_clear_new_message(&aes_instance);
    /* Wait for the end of the decryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_plain_text[0] != output_data[0]) ||
            (ref_plain_text[1] != output_data[1]) ||
            (ref_plain_text[2] != output_data[2]) ||
            (ref_plain_text[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }
}

static void ofb_mode_test(void)
{
    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- OFB cipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_ENCRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_AUTO_START;
    g_aes_cfg.opmode = AES_OFB_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector);
    aes_set_new_message(&aes_instance);
    /* Write the data to be ciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_plain_text);
    aes_clear_new_message(&aes_instance);
    /* Wait for the end of the encryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_cipher_text_ofb[0] != output_data[0]) ||
            (ref_cipher_text_ofb[1] != output_data[1]) ||
            (ref_cipher_text_ofb[2] != output_data[2]) ||
            (ref_cipher_text_ofb[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }

    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- OFB decipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_DECRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_MANUAL_START;
    g_aes_cfg.opmode = AES_OFB_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector);

    /* Write the data to be deciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_cipher_text_ofb);

    aes_set_new_message(&aes_instance);
    aes_start(&aes_instance);
    aes_clear_new_message(&aes_instance);

    /* Wait for the end of the decryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_plain_text[0] != output_data[0]) ||
            (ref_plain_text[1] != output_data[1]) ||
            (ref_plain_text[2] != output_data[2]) ||
            (ref_plain_text[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }
}

static void ctr_mode_test(void)
{
    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- CTR cipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_ENCRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_AUTO_START;
    g_aes_cfg.opmode = AES_CTR_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector_ctr);
    aes_set_new_message(&aes_instance);
    /* Write the data to be ciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_plain_text);
    aes_clear_new_message(&aes_instance);

    /* Wait for the end of the encryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_cipher_text_ctr[0] != output_data[0]) ||
            (ref_cipher_text_ctr[1] != output_data[1]) ||
            (ref_cipher_text_ctr[2] != output_data[2]) ||
            (ref_cipher_text_ctr[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }

    printf("\r\n-----------------------------------\r\n");
    printf("- 128bit cryptographic key\r\n");
    printf("- CTR decipher mode\r\n");
    printf("- Auto start mode\r\n");
    printf("- 4 32bit words\r\n");
    printf("-----------------------------------\r\n");

    state = false;

    /* Configure the AES. */
    g_aes_cfg.encrypt_mode = AES_DECRYPTION;
    g_aes_cfg.key_size = AES_KEY_SIZE_128;
    g_aes_cfg.start_mode = AES_MANUAL_START;
    g_aes_cfg.opmode = AES_CTR_MODE;
    g_aes_cfg.cfb_size = AES_CFB_SIZE_128;
    g_aes_cfg.lod = false;
    aes_set_config(&aes_instance,AES, &g_aes_cfg);

    /* Set the cryptographic key. */
    aes_write_key(&aes_instance, key128);

    /* Set the initialization vector. */
    aes_write_init_vector(&aes_instance, init_vector_ctr);

    /* Write the data to be deciphered to the input data registers. */
    aes_write_input_data(&aes_instance, ref_cipher_text_ctr);

    aes_set_new_message(&aes_instance);
    aes_start(&aes_instance);
    aes_clear_new_message(&aes_instance);
    /* Wait for the end of the decryption process. */
    while (false == state) {
    }

    /* check the result. */
    if ((ref_plain_text[0] != output_data[0]) ||
            (ref_plain_text[1] != output_data[1]) ||
            (ref_plain_text[2] != output_data[2]) ||
            (ref_plain_text[3] != output_data[3])) {
        printf("\r\nKO!!!\r\n");
    } else {
        printf("\r\nOK!!!\r\n");
    }
}

Add to user application initialization (typically the start of main()):

    /* Initialize the system and console*/
    system_init();
    configure_usart();

    aes_get_config_defaults(&g_aes_cfg);
    aes_init(&aes_instance,AES, &g_aes_cfg);

    aes_enable(&aes_instance);

    /* Enable AES interrupt. */
    aes_register_callback(aes_callback,AES_CALLBACK_ENCRYPTION_COMPLETE);
    aes_enable_callback(&aes_instance,AES_CALLBACK_ENCRYPTION_COMPLETE);

Workflow

1. Define sample data from NIST-800-38A appendix F for ECB mode.

   #define AES_EXAMPLE_REFBUF_SIZE 4
   
   /* @{ */
   uint32_t ref_plain_text[AES_EXAMPLE_REFBUF_SIZE] = {
       0xe2bec16b,
       0x969f402e,
       0x117e3de9,
       0x2a179373
   };
   
   uint32_t ref_cipher_text_ecb[AES_EXAMPLE_REFBUF_SIZE] = {
       0xb47bd73a,
       0x60367a0d,
       0xf3ca9ea8,
       0x97ef6624
   };
   
   uint32_t ref_cipher_text_cbc[AES_EXAMPLE_REFBUF_SIZE] = {
       0xacab4976,
       0x46b21981,
       0x9b8ee9ce,
       0x7d19e912
   };
   
   uint32_t ref_cipher_text_cfb128[AES_EXAMPLE_REFBUF_SIZE] = {
       0x2ed93f3b,
       0x20ad2db7,
       0xf8493433,
       0x4afb3ce8
   };
   
   uint32_t ref_cipher_text_ofb[AES_EXAMPLE_REFBUF_SIZE] = {
       0x2ed93f3b,
       0x20ad2db7,
       0xf8493433,
       0x4afb3ce8
   };
   
   uint32_t ref_cipher_text_ctr[AES_EXAMPLE_REFBUF_SIZE] = {
       0x91614d87,
       0x26e320b6,
       0x6468ef1b,
       0xceb60d99
   };
   
   const uint32_t key128[4] = {
       0x16157e2b,
       0xa6d2ae28,
       0x8815f7ab,
       0x3c4fcf09
   };
   
   const uint32_t init_vector[4] = {
       0x03020100,
       0x07060504,
       0x0b0a0908,
       0x0f0e0d0c
   };
   
   const uint32_t init_vector_ctr[4] = {
       0xf3f2f1f0,
       0xf7f6f5f4,
       0xfbfaf9f8,
       0xfffefdfc
   };
   
   /* @} */

2. Create related module variable and software instance structure.

   /* Output data array */
   static uint32_t output_data[AES_EXAMPLE_REFBUF_SIZE];
   /* State indicate */
   volatile bool state = false;
   
   struct aes_config g_aes_cfg;
   struct aes_module aes_instance;
   struct usart_module usart_instance;

3. Configure, initialize, and enable AES module.
   1. Configuration AES struct, which can be filled out to adjust the configuration of a physical AES peripheral.

          aes_get_config_defaults(&g_aes_cfg);

   2. Initialize the AES configuration struct with the module's default values.

          aes_init(&aes_instance,AES, &g_aes_cfg);

   3. Enable the AES module.

          aes_enable(&aes_instance);

   4. Register and enable the AES module callback.

          /* Enable AES interrupt. */
          aes_register_callback(aes_callback,AES_CALLBACK_ENCRYPTION_COMPLETE);
          aes_enable_callback(&aes_instance,AES_CALLBACK_ENCRYPTION_COMPLETE);

Use Case

Code

Copy-paste the following code to your user application:

    ecb_mode_test();
    cbc_mode_test();
    cfb128_mode_test();
    ofb_mode_test();
    ctr_mode_test();

Workflow

1. Configure ECB mode encryption and decryption and run test.

       ecb_mode_test();

2. Configure CBC mode encryption and decryption and run test.

       cbc_mode_test();

3. Configure CFB mode encryption and decryption and run test.

       cfb128_mode_test();

4. Configure OFB mode encryption and decryption and run test.

       ofb_mode_test();

5. Configure CTR mode encryption and decryption and run test.

       ctr_mode_test();