encryption and decryption of advertising data

[Naralasetty Praneeth]

Hii nordic;

I need to encrypt and decrypt my advertising data i.e;UUID,Major,Minor,etc.;  of my nrf52832

So it cannot be seen by third parties

my sdk version is 15.2 and softdevice is 132

[Naralasetty Praneeth]

bjorn-spockeli:

I think i had done the same that you told in the above code then also i am not getting the values 

Please help me to write that code

[bjorn-spockeli]

You can start by modifying the BLE peripheral code so that the nounce that you generate is placed in the Scan response packet. This is done by populating the ble_advdata_t srdata struct in the ble_advertising_init_t init struct in advertising_init() in main.c

/**@brief Function for initializing the Advertising functionality.
 */
static void advertising_init(void)
{
    ret_code_t             err_code;
    ble_advertising_init_t init;

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

    init.advdata.name_type               = BLE_ADVDATA_FULL_NAME;
    init.advdata.include_appearance      = true;
    init.advdata.flags                   = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;
    init.advdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
    init.advdata.uuids_complete.p_uuids  = m_adv_uuids;
    
    // Populate Scan Response Data struct
    ble_advdata_manuf_data_t sr_advdata;

    memset(&sr_advdata,0, sizeof(sr_advdata));
    sr_advdata.data.p_data = nounce;
    sr_advdata.data.size = sizeof(nounce);
    sr_advdata.company_identifier = 0x0059; // Nordic Semiconductor Company ID, should be replaced with own company ID. 

    init.srdata.p_manuf_specific_data = &sr_advdata;


    init.config.ble_adv_fast_enabled  = true;
    init.config.ble_adv_fast_interval = APP_ADV_INTERVAL;
    init.config.ble_adv_fast_timeout  = APP_ADV_DURATION;

    init.evt_handler = on_adv_evt;

    err_code = ble_advertising_init(&m_advertising, &init);
    APP_ERROR_CHECK(err_code);

    ble_advertising_conn_cfg_tag_set(&m_advertising, APP_BLE_CONN_CFG_TAG);
}

[Naralasetty Praneeth]

bjorn-spockeli:

yes its done i had added nounce to the scan response.

now what is the code that i should add in the central side i.e., Scanning side

this code is for peripheral side usinf ble_app_proximity_beacon:

encryption peripheral.rar

decryption central.rar

this is code i wrote using ble_app_uart_c example for decryption.Please check i am getting garbage values not getting the encrypted values

[Naralasetty Praneeth]

Hi  bjorn-spockeli

Please respond 

[bjorn-spockeli]

I did not see any reference any code that added the nounce to the scan response data in the ble_app_proximity_beacon example that was attached. I added this the following way.

static void advertising_init(void)
{
    uint32_t      err_code;
    ble_advdata_t advdata;
    ble_advdata_t scandata;
    uint8_t       flags = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;

    ble_advdata_manuf_data_t manuf_specific_data;

    manuf_specific_data.company_identifier = APP_COMPANY_IDENTIFIER;

#if defined(USE_UICR_FOR_MAJ_MIN_VALUES)

    uint16_t major_value = ((*(uint32_t *)UICR_ADDRESS) & 0xFFFF0000) >> 16;
    uint16_t minor_value = ((*(uint32_t *)UICR_ADDRESS) & 0x0000FFFF);

    uint8_t index = MAJ_VAL_OFFSET_IN_BEACON_INFO;

    m_beacon_info[index++] = MSB_16(major_value);
    m_beacon_info[index++] = LSB_16(major_value);

    m_beacon_info[index++] = MSB_16(minor_value);
    m_beacon_info[index++] = LSB_16(minor_value);
#endif

    manuf_specific_data.data.p_data = (uint8_t *) m_beacon_info;
    manuf_specific_data.data.size   = APP_BEACON_INFO_LENGTH;

    m_beacon_info[18] = 0x00;
    m_beacon_info[19] = 100; // init battery
 
    m_beacon_info[20] = 0x00;
    m_beacon_info[21] = 0x00;


    memset(&advdata, 0, sizeof(advdata));
    advdata.flags                 = flags;
    advdata.p_manuf_specific_data = &manuf_specific_data;



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

    m_adv_params.properties.type = BLE_GAP_ADV_TYPE_CONNECTABLE_SCANNABLE_UNDIRECTED;
    m_adv_params.p_peer_addr     = NULL;    
    m_adv_params.filter_policy   = BLE_GAP_ADV_FP_ANY;
    m_adv_params.interval        = NON_CONNECTABLE_ADV_INTERVAL;
    m_adv_params.duration        = 0;       

    err_code = ble_advdata_encode(&advdata, m_adv_data_buffer_1.adv_data.p_data, &m_adv_data_buffer_1.adv_data.len);
    APP_ERROR_CHECK(err_code);

    ble_advdata_manuf_data_t sr_manuf_data;

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

    sr_manuf_data.data.p_data = nounce;
    sr_manuf_data.data.size = sizeof(nounce);
    sr_manuf_data.company_identifier = APP_COMPANY_IDENTIFIER;

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

    //scandata.name_type             = BLE_ADVDATA_FULL_NAME;
    scandata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
    scandata.uuids_complete.p_uuids  = m_adv_uuids;
    scandata.p_manuf_specific_data = &sr_manuf_data;

    ble_gap_addr_t gap_address;
    gap_address.addr_type = BLE_GAP_ADDR_TYPE_PUBLIC;
    memcpy(&gap_address.addr, "\xbb\xaa\xcc\xbb\xaa\xAC", sizeof(gap_address.addr));
    err_code = sd_ble_gap_addr_set(&gap_address);
    APP_ERROR_CHECK(err_code);

    err_code = ble_advdata_encode(&scandata, m_adv_data_buffer_1.scan_rsp_data.p_data, &m_adv_data_buffer_1.scan_rsp_data.len);
    APP_ERROR_CHECK(err_code);
    err_code = ble_advdata_encode(&scandata, m_adv_data_buffer_2.scan_rsp_data.p_data, &m_adv_data_buffer_2.scan_rsp_data.len);
    APP_ERROR_CHECK(err_code);

    err_code = sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data_buffer_1, &m_adv_params);
    APP_ERROR_CHECK(err_code);
}

On the central side you have come a bit on the way. However, I would recommend filtering the ADV reports on a specific ID in the scan response manufacturing data as you now are processing all advertisement reports. In the ble_app_proximity_beacon example you are adding a lot of service UUIDs which doesnt are not used. I would remove these as these take up space in the scan response packet. 

You can use the ble_advdata_search() function  from ble_advdata.c to find the manufacturing data by setting the ad_type input parameter set to BLE_GAP_AD_TYPE_MANUFACTURER_SPECIFIC_DATA. This will give you the offset indicating where the manufacturing data starts. 

Best regards

Bjørn