Security of External Flash DA16200

Hi, 

thank you for your support! I have seen the documentation UM-WI-046 chap. 9 and as wrote in the previous reply I understand that the NVRAM writes is item oriented.                                                              

Now I have found in the code that there are two list of items (INT and STRING) defined as enums.

typedef enum {

     /// DA16200 MAC Address in NVRAM (set only)

     DA16X_CONF_STR_MAC_NVRAM,

     /// DA16200 MAC Spoofing (set only)

     DA16X_CONF_STR_MAC_SPOOFING,

     /// DA16200 MAC in OTP (set only)

    ................................                                                                                                                                              }

1) e.g. if I want to save my AES key, should I add an enum such as DA16X_CUSTOM_AES_UART_128BIT_KEY to the STRING list?

And then I use the setenv command :

nvram.setenv DA16X_CUSTOM_AES_UART_128BIT_KEY 01-02-03-04-05-06-07-08-09-AA-BB-CC-DD-EE-FF

2) Does the firmware automatically store my key at the right address so that I see the NVRAM as a black box?

3) For instance I want to to store a key of 128 bit , how I could know if there is enough space in the NVRAM?                                         

Best Regards

Hi There,

Thank you for the reply.
Please find below the answers to your questions:

1. If I want to save my AES key, should I add an enum such as DA16X_CUSTOM_AES_UART_128BIT_KEY to the STRING list?
And then I use the setenv command.

-> An tsetenv command can be used to store user data in NVRAM without adding Items.
      tsetenv : tsetenv [temporary var] [string]
      ex) tsetenv DA16X_CUSTOM_AES_UART_128BIT_KEY 01-02-03-04-05-06-07-08-09-AA-BB-CC-DD-EE-FF

2. Does the firmware automatically store my key at the right address so that I see the NVRAM as a black box?
   -> The user key can be stored encrypted in the NVRAM area after applying secure NVRAM.

3. For instance I want to to store a key of 128 bit , how I could know if there is enough space in the NVRAM?   

   -> Available max NVRAM space is 4KB and can check the current usage size through getenv command.

      
Best Regards,
OV_Renesas

Hi,

Thank you for your feedback.

I have followed this procedure:

1) As First step, in the firmware I  get my secret key with this API. 

- Secret_key = char *read_nvram_string(DA16X_CUSTOM_AES_UART_128BIT_KEY).  

I have added API function in user_main.c, as you can seen in the image below:

int user_main(char init_state)
{
    int	status = 0;
    char aes_key[70];
	char *p = aes_key;
	......................
	......................
	......................
    PRINTF("Loading AES Key from NVRAM...\n");
    
	p = read_nvram_string("DA16X_CUSTOM_AES_UART_128BIT_KEY");

	if (p == NULL) {
			PRINTF("ERROR: AES Key Read Failed! Using Default Key\n");
			memset(aes_key, 0, sizeof(aes_key));  // Clear memory
	} else {
		PRINTF("AES Key Read from NVRAM: ");
		for (int i = 0; i < 70; i++) {
		    PRINTF("%c ", aes_key[i]);
		}
		PRINTF("\n");

		PRINTF("AES Key Loaded Successfully!\n");
	}
    ..............
    ..............
    ..............
    return status;
}

2) Build project with with the changes made and Flashing images firmware using tera term console;

3) Open UART0 and From debug console send the command tsetenv :

4) reset, and reboot and AES Key Read from NVRAM is shown in the following capture :

The result is not expected output. how does this happen?

5) I have used the command getenv and I verify that effectivly i read the right string that temporary set with tsetenv command.

I have tried also using known ITEM in your project, but is the same error output after reading nvram  .

Furthermore I think there is an error in your UM-WI-046: in the description of char * read_nvram_string()

you mention “Read an integer” while I suppose the right sentence should be “Read a string”

Best regards

Hi There,

Thank you for the reply.

The user can read the key data in NVRAM using the read_nvram_string().

Thank you for checking the error in UM-WI-046 and we will fix it with "Read a string value".


Best Regards,
OV_Renesas

Hi,

I am tried to read AES key from NVRAM using char *read_nvram_string as showed in the following code . I have added API function in the following file of SDK project (da16200/customer_aap/src/user_main/user_main.c).

int user_main(char init_state)
{
    int	status = 0;
    char aes_key[70];
	char *p = aes_key;
	.....................
    .....................

    PRINTF("Loading AES Key from NVRAM...\n");

	p = read_nvram_string("DA16X_CUSTOM_AES_UART_128BIT_KEY");

	if (p == NULL) {
			PRINTF("ERROR: AES Key Read Failed! Using Default Key\n");
			memset(aes_key, 0, sizeof(aes_key));  // Clear memory
	} else {
		//PRINTF("AES Key Read from NVRAM: %s\n", aes_key);
		PRINTF("AES Key Read from NVRAM: ");
		for (int i = 0; i < 70; i++) {
		    PRINTF("%c ", aes_key[i]);
		}
		PRINTF("\n");

		PRINTF("AES Key Loaded Successfully!\n");
	}
.................

    return status;
}

The output in the tera term console is not as expected. The characters are mismatched, they do not display correctly ! 

How solve this mismatching?

Hi There,

Thank you for the reply and apologies for the delay.
There were some mismatches in the example code.
We provide an example to write and read a custom key in NVRAM.
Please find attached the Secure_NVRAM.zip file.
It contains
- ReadMe
- Example code
- Console Log.

Please let us know if you have any other questions or requests.

Best Regards,
OV_Renesas
 Secure_NVRAM.zip