Re: Securing BLE device communication without OOB pairing (multiple devices)


Vikrant More <vikrant8051@...>
 

Awesome, thanks! 

>>If he/she clicks on "yes" then only process go ahead.
>>[ Here APP will only connect to Devices which are in vicinity by >>checking their signal strength (RSSI) ]
>>So I think, this method may solve the issue of Authentication. Am >>I right ?

But I'm waiting for solution for above mentioned query.

If am using Human to authenticate, his own device just before ECDH key agreement process, is that enough in case of no OOB channel?

As per my understanding, problem arises only when user click on "YES" even when he has not seen Blinking LED. That means user App is connected to attacker Device & it will share #CommonKey of his devices to attacker.

Are there any flaws in this mechanism besides this ?

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Have you seen, this video about #BluetoothMesh ? I think Bluetooth SIG has twitted about them sometimes before.

As per my understanding, they have not used input OOB, output OOB or static OOB for authentication.

On my inquiry, they reply as:


"The authentification is automatic, comming from the signal power measured by the smartphone. You have to go 15/20cm from the device you want to pair."


In this case, what is your opinion ?
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Alternate Way (which is final solution if there is no OOB channel for authentication):

Device after flashing firmware on it whenever get power will generate random no. & stored it on flash memory & will not create it again in future. 

Then after every reboot it will send that random no. on device UART terminal.

Based on that unique Random no. manufacturer has to create QR code & label it on that device.

This is most secured way but some people will not understand its importance since as company it will be burden for them. 

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On Mar 4, 2018 11:48 AM, "Johan Hedberg" <johan.hedberg@...> wrote:
Hi Vikrant,

Zephyr's Bluetooth stack exposes ECC as standard HCI commands & events
through subsys/bluetooth/host/hci_ecc.c. And you're right that it's the
FIPS P-256 curve that both LE Secure Connections (LE Security Manager
enhancement that debuted with Bluetooth 4.1) and Mesh Provisioning use.
The micro-ecc library that TinyCrypt has a copy of can be found here:

ext/lib/crypto/tinycrypt/source/ecc*.c

The main header file is here:

ext/lib/crypto/tinycrypt/include/tinycrypt/ecc.h

Johan

On Sun, Mar 04, 2018, Vikrant More wrote:
> Hi Johan,
>
> https://github.com/kmackay/micro-ecc has support for 5 standard curves:
> secp160r1, secp192r1, secp224r1, secp256r1, and secp256k1.
>
> Out of *secp256r1* and *secp256k1*, which one is used by Zephyr
> #BluetoothMesh ?
>
> As per #BluetoothMesh specs, it should be FIPS-P256 curve.
> Is Zephyr built in *micro*-*ecc* library different than what I am currently
> using ?
>
> Thank You!!
>
> On Sun, Mar 4, 2018 at 1:16 AM, Vikrant More <vikrant8051@...> wrote:
>
> > Hi Johan,
> >
> > Thanks for reply !!
> >
> > Ok, but I don't know how to integrate & use it in my current project since
> > there is no any documentation available about it.
> > So I chose alternate way but will figure out how to use Zephyr's library
> > in coming days.
> >
> > >>Before this, Admin will Blink LED on BLE Device before transferring
> > #CommonKey to it using Smartphone App.
> > >>Once user confirm it, then only #CommonKey get transfer as command to
> > 3rd characteristic & BLE device save it as #CommonKey.
> >
> > >>>>You can acheive confidentiality with the ECDH method, but without some
> > >>>>OOB mechanism you won't be able to securely authenticate the peer
> > you're
> > >>>>talking to. So I don't see this as any different than doing pairing
> > >>>>using NoInputNoOutput as the IO capability.
> >
> > Here, before initiating ECDH to generate share secret , Smartphone App
> > will send commands to LED lights that will blink it for while
> > & App will ask Admin User -> "Have you seen any Blinking LED ?"
> >
> > If he/she clicks on "yes" then only process go ahead.
> > [ Here APP will only connect to Devices which are in vicinity by checking
> > their signal strength (RSSI) ]
> > So I think, this method may solve the issue of Authentication. Am I right ?
> >
> > May be it is not enough....but I don't have any other option since LED
> > Lights generally does not have OOB channels.
> > I can't use NFC since not every phone have that feature. So ... ??
> >
> > Thank You !!
> >
> > On Sat, Mar 3, 2018 at 9:18 PM, Johan Hedberg <johan.hedberg@...>
> > wrote:
> >
> >> Hi Vikrant,
> >>
> >> micro-ecc is what the Zephyr TinyCrypt uses, and it is also what the
> >> Zephyr Bluetooth Security Manager (LE pairing) and mesh implementations
> >> use, so no need to start installing micro-ecc separately.
> >>
> >> You can acheive confidentiality with the ECDH method, but without some
> >> OOB mechanism you won't be able to securely authenticate the peer you're
> >> talking to. So I don't see this as any different than doing pairing
> >> using NoInputNoOutput as the IO capability.
> >>
> >> Johan
> >>
> >> On Sat, Mar 03, 2018, Vikrant More wrote:
> >> > Hello World !!
> >> >
> >> > I found solution as micro-ecc library -> https://github.com/kmackay/
> >> > micro-ecc
> >> > to generate #AdminKey or Master key on both sides without transferring
> >> > it on insecure Bluetooth Link.
> >> >
> >> > Thank You !!
> >> >
> >> > On Sat, Mar 3, 2018 at 12:57 PM, Vikrant More <vikrant8051@...>
> >> wrote:
> >> >
> >> > > Hello,
> >> > >
> >> > > How to use ECDH mechanism to establish common #AdminKey or Master Key,
> >> > > using functions defined in $zephyr_base/subsys/bluetooth/host/ecc.h
> >> for
> >> > > normal BLE devices ?
> >> > >
> >> > > We uses this concept, in Bluetooth Mesh where every time new
> >> > > Public-Private Key pair get generated on both sides,
> >> > > using which a Master key established after public keys get exchange
> >> over
> >> > > insecure channel.
> >> > >
> >> > > I think it will solve my issue. How to check this mechanism without
> >> > > Android/iOS App after implemented it on Device side ?
> >> > >
> >> > > Thank You !!
> >> > >
> >> > > On Fri, Mar 2, 2018 at 11:20 PM, Vikrant More <vikrant8051@...>
> >> > > wrote:
> >> > >
> >> > >> Hello,
> >> > >> If I enabled encryption or authentication to access BLE device
> >> > >> characteristic, we have to do OOB pairing.
> >> > >>
> >> > >> But in some cases, it is not possible like budget LED lights. In this
> >> > >> case, how to make secure communication at Zephyr App level using
> >> security
> >> > >> keys ?
> >> > >>
> >> > >> ------------------------------------------------------------
> >> > >> ----------------------------------------
> >> > >> This is my implementation where there are 3 characteristics:
> >> > >> 1) 1st (read) characteristic always generates 16 bytes of random data
> >> > >> 2) 2nd (write) characteristic used for authentication
> >> > >> 3) 3rd (write) characteristic which accepts commands
> >> > >>
> >> > >> When BLE device is in factory reset mode,
> >> > >> then Smartphone App read random data from 1st Characteristic & save
> >> it as
> >> > >> #AdminKey (AES-128) for that device.
> >> > >>
> >> > >> Then it again requests(read) another random data from 1st
> >> characteristic
> >> > >> , encrypt it using #AdminKey & send to 2nd characteristic.
> >> > >>
> >> > >> On BLE device side, it will decrypt data using #AdminKey & compare it
> >> > >> with recently send random data. If data matched then BLE device saves
> >> > >> #AdminKey on self flash memory.
> >> > >>
> >> > >> So every device will have unique #AdminKey.
> >> > >>
> >> > >> Now here after, Smartphone who send encrypted random data which is
> >> > >> encrypted using #AdminKey to 2nd characteristic will get #admin
> >> access.
> >> > >> (Random Data from 1st Characteristic)
> >> > >>
> >> > >> Now if I wanna give access to my guests or family members, then in
> >> that
> >> > >> case I have to set 16-bytes of #CommonKey (manually entered number)
> >> for all
> >> > >> BLE devices.
> >> > >>
> >> > >> Before this, Admin will Blink LED on BLE Device before transferring
> >> > >> #CommonKey to it using Smartphone App. Once user confirm it, then
> >> only
> >> > >> #CommonKey get transfer as command to 3rd characteristic & BLE
> >> device save
> >> > >> it as #CommonKey.
> >> > >>
> >> > >> As name suggest, #CommonKey is same for all devices. So here onward,
> >> > >> Smartphone who send encrypted random data using #CommonKey will get
> >> #guest
> >> > >> access of that BLE device. Using #guest access, in case of LED
> >> lights user
> >> > >> can only do On/Off & intensity control.
> >> > >>
> >> > >> So 3rd characteristic only accept commands when user authentic
> >> itself as
> >> > >> #admin or #guest.
> >> > >>
> >> > >> Can I go ahead with this method ?
> >> > >>
> >> > >> But I think it is not secure, since data is exchanged over
> >> unencrypted
> >> > >> link. Isn't it ?
> >> > >>
> >> > >> Is somebody has better robust secure solution as per my requirements
> >> ?
> >> > >>
> >> > >> Thank You !!
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >>
> >> > >
> >>
> >
> >

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