Usage of CRYPTO LIBRARY

[ABatt.1]

I am trying to use the cryptographic library on a STM32F103, but I cannot find any documentation that is in line with the library and functions.

In UM1924 rev.8 we still speak of version 3, but I cannot find the mnual consideration of rev. 4.0.1 (there is no user manual on the cdocumentation page).

Where can I find the documentation for the correct management of the library functions?

Thank you all for your support

[Tesla DeLorean]

https://wiki.st.com/stm32mcu/wiki/Security:Getting_started_with_the_Cryptographic_Library

[ABatt.1]

Hi the wiki was useful, but i'm an implementation issue and I can't figure out where is the problem.

I started from example in ...\STM32CubeExpansion_Crypto_V4.0.1\Projects\NUCLEO-G071RB\Applications\Cipher\AES_CBC_EncryptDecrypt\Src

In order to keep main clear, I wrote an Crypto_Inizializzazione() function like this:

cmox_cbc_handle_t Cbc_Ctx;
cmox_cipher_retval_t retval;
 
const uint8_t Key[] = {'1','2','3','4','5','6','7','8','9','1','2','3','4','5','6','7'};
const uint8_t IV[] = {'1','2','3','4','5','6','7','8','9','1','2','3','4','5','6','7'};
 
 
uint8_t Crypto_Inizializzazione(cmox_cipher_handle_t * cipher_ctx ){
 
	/* Initialize cryptographic library */
	if (cmox_initialize(NULL) != CMOX_INIT_SUCCESS){
		return 1;
	}
 
	/* Cleanup the context */
	//retval = cmox_cipher_cleanup(cipher_ctx);
	//if (retval != CMOX_CIPHER_SUCCESS){
	//	return 2;
	//}
 
	cipher_ctx = cmox_cbc_construct(&Cbc_Ctx, CMOX_AESSMALL_CBC_ENC);
	if (cipher_ctx == NULL){
		return 3;
	}
 
	/* Initialize the cipher context */
	retval = cmox_cipher_init(cipher_ctx);
	if (retval != CMOX_CIPHER_SUCCESS){
		return 4;
	}
 
	/* Setup of the encryption key into the context */
	retval = cmox_cipher_setKey(cipher_ctx, Key, sizeof(Key)); /* AES key to use */
	if (retval != CMOX_CIPHER_SUCCESS){
		return 5;
	}
 
	/* Setup of the Initialization Vector (IV) into the context */
	retval = cmox_cipher_setIV(cipher_ctx, IV, sizeof(IV)); /* Initialization vector */
	if (retval != CMOX_CIPHER_SUCCESS){
		return 6;
	}
 
	return 0;
}

In main I read 16 bytes from SD, encrypt it, and I write encrypted 16 bytes on SD (in another file).

int main(void)
{
 /* USER CODE BEGIN 1 */
	FATFS StrutturaCtrFS;
	FIL File_RD, File_WD; /* File objects */
	FRESULT Risultato;
	uint8_t Risultato_tmp;
	FILINFO fno;
	cmox_cipher_handle_t * cryptoHandler;
	cmox_cipher_retval_t CRYRisultato;
	size_t computed_size;
	char NOME_FILE[13], buffer[13];
	uint8_t BufferTest_1[16], BufferTest_2[16];
 
 /* USER CODE END 1 */
 
 /* MCU Configuration--------------------------------------------------------*/
 
 /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
 HAL_Init();
 
 /* USER CODE BEGIN Init */
 
 /* USER CODE END Init */
 
 /* Configure the system clock */
 SystemClock_Config();
 
 /* USER CODE BEGIN SysInit */
 
 /* USER CODE END SysInit */
 
 /* Initialize all configured peripherals */
 MX_GPIO_Init();
 MX_DMA_Init();
 MX_SPI2_Init();
 MX_ADC1_Init();
 MX_USART1_UART_Init();
 MX_USART3_UART_Init();
 MX_CRC_Init();
 MX_FATFS_Init();
 /* USER CODE BEGIN 2 */
 
 //Accendo le periferiche
 BACKLIGHT_ON();
Risultato_tmp = Crypto_Inizializzazione(cryptoHandler);
 if(0 != Risultato_tmp){
	while(1);
 }
 
 Risultato = f_mount(&StrutturaCtrFS,"",1);
 if(FR_OK != Risultato){
	 while(1);
 }
 
 memcpy(NOME_FILE,"Upgrade.bin",12);
 Risultato = f_open(&File_RD,NOME_FILE, FA_READ);
 if(FR_OK != Risultato){
	 while(1);
 }
 
 memcpy(NOME_FILE,"Upgrade.out",12);
 Risultato = f_open(&File_WD,NOME_FILE, FA_CREATE_ALWAYS | FA_WRITE);
 if(FR_OK != Risultato){
	 f_close(&File_RD);
	 while(1);
 }
 
 numBytes = 16;
 while(numBytes > 15){
	 f_read(&File_RD,BufferTest_1, 16, &numBytes);
	 if(numBytes < 16){
		 memset(&BufferTest_1[numBytes],0xFF,(16-numBytes));
	 }
	 memset(BufferTest_2,0,16);
	 CRYRisultato = cmox_cipher_append(cryptoHandler,(const uint8_t *)BufferTest_1, (size_t)16,BufferTest_2, &computed_size);
	 f_write(&File_WD,BufferTest_2, computed_size, &numBytes);
 }
 
 f_close(&File_RD);
 f_close(&File_WD);
 BACKLIGHT_OFF();
 while(1);

Init of cypher is ok (return 0), but cmox_cipher_append return code 0x10003 (I thinks is CMOX_CIPHER_ERR_BAD_PARAMETER) and computed_size is 0.

I checked every input parameter (adding also a cast) but I don't fined the issue.

The only questionable point is the cmox_cipher_handle_t * cryptoHandler pointer: I do not make any memory allocation for this pointer. it's correct ? it is the task of the cmox_cbc_construct function ?

Where I can find futher information ?

[ABatt.1]

Has anyone ever had the same problem as me?

[Tesla DeLorean]

I'd wager money on it..

Problem solving typically revolves around finding what the problem is and fixing it, and doesn't necessarily require someone to have previously come up with a solution. Apply reason and logic.

You aren't going to get the assignment back into main() the way you've constructed this. You'd presumably need a pointer to a pointer