Function to encrypt all data to be sent

[codebreaker176]

Hi,

Based on other discussions of encryption etc , I created a function to encrypt all the data, so that whenever I call the function It encrypts.

static   nrf_ecb_hal_data_t aes_struct;

static  uint8_t aes_data[16];

static   uint8_t aes_data_decrypted[16];

//Initializing arrays

memset (&aes_struct, 0, sizeof(aes_struct));

memset (aes_data, 0, sizeof(aes_data));

memset (aes_data_decrypted, 0, sizeof(aes_data_decrypted));

uint8_t* encrypt(uint8_t* p_data)
 {



        //Initializing key

        for (int i = 0; i < 16; i++)

        {
            aes_struct.key [i] = i;
        }

        //Initializing nouncence

        memset (aes_struct.cleartext, 0xaa, sizeof(aes_struct.cleartext)); //todo: use more random data and add counter

        //Creating chipertext

        sd_ecb_block_encrypt(&aes_struct); 

        //Encrypt -> XOR chipertext with p_data:



        for (int i = 0; i < length; i++)

        {  
            aes_data[i] = p_data [i] ^ aes_struct.ciphertext[i];
        }


        //decrypt -> XOR chipertext with Encrypted data:

        return (aes_data);

 }

 uint8_t* decrypt(uint8_t* p_data)
 {
    for (int i = 0; i < length; i++)

        {  
            aes_data[i] = p_data [i] ^ aes_struct.ciphertext[i];
        }


        //decrypt -> XOR chipertext with Encrypted data:

        return (aes_data);
 }

But I am not able to call the function, there's always an error

uint8_t vib_cnt_buf[5];
Convert_to_ascii(right,(&vib_cnt_buf[0]),8);
&vib_cnt_buf = encrypt(&vib_cnt_buf); //Encrypting this data

Can you please help

[ovrebekk]

Hi

Are you able to provide some more information on the error you are seeing?

Is it the Convert_to_ascii(..) function that returns the error?

Are you able to share the implementation of this function with me?

Best regards
Torbjørn

[codebreaker176]

Hi again,

Error : lvalue required as left operand of assignment

this error is at this lilne : &vib_cnt_buf = encrypt(&vib_cnt_buf);

I can't seem to get rid of it at all

the convert_to_ascii() function works well and converts the same variable to ascii values 

[ovrebekk]

Hi 

Sorry, I didn't notice that line earlier, it is clearly an illegal operation. 

You are taking a pointer to a pointer to the vib_cnt_buf array and trying to assign a pointer to it, this will not work. 

Instead I would suggest doing something like this:

uint8_t *encrypted_data_ptr = encrypt(&vib_cnt_buf);
memcpy(vib_cnt_buf, encrypted_data_ptr, length);

Best regards
Torbjørn

[codebreaker176]

Hello,

There is another error in the above mentioned code at line 9 : memset (&aes_struct, 0, sizeof(aes_struct));

Error : expected declaration specifiers or '...' before '&' token.

Thanks for the support

[codebreaker176]

Hello,

I am now using ECB mode of AES, there were lot of errors in previous one.

Now in the below code for ECB mode I have just one error : which I can't figure out the meaning,

static void nus_data_handler(ble_nus_evt_t * p_evt)
{   
    //some codes over here

    Convert_to_ascii(Battery_voltage,(&vib_cnt_buf[0]),4);
    uint32_t *encrypted_data_ptr = ctr_encrypt(&vib_cnt_buf);
    memcpy(vib_cnt_buf, encrypted_data_ptr, length);
    err_code = ble_nus_data_send(&m_nus, (&vib_cnt_buf), &thi, m_conn_handle);
}
/* 
.
.
.
.   
.
.
.
 */
static uint32_t crypt(uint8_t * buf)
{
    uint8_t  i;
    uint32_t err_code;

    if (!m_initialized)
    {
	    return NRF_ERROR_INVALID_STATE;
    }

    err_code = sd_ecb_block_encrypt(&m_ecb_data);
    if (NRF_SUCCESS != err_code)
    {
	    return err_code;
    }

    for (i=0; i < ECB_KEY_LEN; i++)
    {
	    buf[i] ^= m_ecb_data.ciphertext[i];
    }

    // Increment the counter.
    (*((uint32_t*) m_ecb_data.cleartext))++;

    return NRF_SUCCESS;
}


uint32_t ctr_encrypt(uint8_t * p_clear_text)
{
    return crypt(p_clear_text);
}


uint32_t ctr_decrypt(uint8_t * p_cipher_text)
{
    return crypt(p_cipher_text);
}

The following line has error (line 47 in above snippet) : 

uint32_t ctr_encrypt(uint8_t * p_clear_text)

{

}

Error : conflicting types for 'ctr_encrypt'