How to know when BLE link is encrypted?

I have not tried this myself but as I understand there is a parameter for each attribute which can be configured to require encryption before a read or write procedure can be carried out. The constant values are:

#define GATT_PERMIT_AUTHEN_READ 0x04 //!< Read requires Authentication
#define GATT_PERMIT_AUTHEN_WRITE 0x08 //!< Write requires Authentication
#define GATT_PERMIT_AUTHOR_READ 0x10 //!< Read requires Authorization
#define GATT_PERMIT_AUTHOR_WRITE 0x20 //!< Write requires Authorization

I am unsure what the difference between authentication and authorization - maybe someone can clarify

Hi Richard,

As you mentioned that you are registering your Bond Manager callbacks with GAPBondMgr_Register(). I think using pairStateCB callback you can track the pairing status for the central device.

I think this will be helpful to you :

static void CentralPairStateCB( uint16 connHandle, uint8 state, uint8 status )
{
  if ( state == GAPBOND_PAIRING_STATE_STARTED )
  {
    // Pairing started
  }
  else if ( state == GAPBOND_PAIRING_STATE_COMPLETE )
  {
    if ( status == SUCCESS )
    {
      // Pairing success
    }
    else
    {
      // Pairing fail
    }
  }
  else if ( state == GAPBOND_PAIRING_STATE_BONDED )
  {
    if ( status == SUCCESS )
    {
      // Bonding success
    }
  }
}

I have tried to add GATT_PERMIT_AUTHEN_WRITE to one of the attributes, thinking like you that the stack might hold off the write until the link is authenticated, but in fact the result is a disconnect.

Hi Maulik,

As I mentioned in the original post, I have registered with GAPBondMgr_Register(), but in fact none of the callbacks are ever called.

Richard

Upon examining GAPBondMgr_Register() code one see's the following:

         // Register with GATT Server App for event messages
         GATTServApp_RegisterForMsg( gapBondMgr_TaskID );

The problem is that a central device is GATT client, so there is no GATT server running.  It seems that TI has unnecessarily conflated security with central/peripheral roles.

Hi Richard,

Did you checked the GlucoseCollector Example. I think the callbacks you need to register is not in GATTServApp_RegisterForMsg() function. You need to register the callbacks in GAPBondMgr_Register() function. This function takes two callbacks to register and that is

typedef struct
{
  pfnPasscodeCB_t     passcodeCB;       //!< Passcode callback
  pfnPairStateCB_t    pairStateCB;      //!< Pairing state callback
} gapBondCBs_t;

Here using the pairStateCB you can keep track of the status of pairing.

I hope we both are on the same page. What I am getting is, you want to know that when the link is being encrypted by the master. pairStateCB can do this thing for you as far I know.

Please checkout the GlucoseCollector example and glucCollCentralPairStateCB() for more details if we both are on same page.

Best Regards,

Maulik.

Hi Maulik,

Thanks for the suggestion, the Glucose examples were helpful.  

Richard