Subject: Re: [Cfrg] Encrypt in place guidance / Similarities to BLE use-cases

From: Björn Haase <[email-masked]>
Date: Wed, 1 Apr 2020 11:09:59 +0000

>There is no way the basic messages are changing and expanding as long as BT4 is used.

Actually regarding BLE, this is possible. You could dynamically modify the content of the different AD and additional data fields. There is a manufacturer specific data field that could be used for this purpose, still payloads are restricted to roughly 25 bytes when you aim at keeping compatibility with all the different iOS, Android and windows platforms. Note still, that this is significantly longer than 8 bytes (but still too short for the conventional 128 bit nonce and MAC fields).

I agree that none of the standardized protocol messages for advertising considers security, to my best knowledge.

Yours,

Björn.

Mit freundlichen Grüßen I Best Regards 

Dr. Björn Haase 

Senior Expert Electronics | TGREH Electronics Hardware

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Von: Robert Moskowitz <[email-masked]>
Gesendet: Mittwoch, 1. April 2020 12:58
An: Björn Haase <[email-masked]>; Salz, Rich <rsalz=[email-masked]>; Blumenthal, Uri - 0553 - MITLL <[email-masked]>; Dan Brown <[email-masked]>; [email-masked]
Betreff: Re: [Cfrg] Encrypt in place guidance

There is no way the basic messages are changing and expanding as long as BT4 is used.

There is an auth message that can carry multiple basic messages.  We have a draft in DRIP:

draft-wiethuechter-drip-auth

That provides message protection.  This is up to 10 chained BT4 broadcasts.  Or 1 BT5 broadcast.

Yes, replay attacks are pretty much built into this architecture.  The major vendors don't get it or don't care (many are chinese companies).  The regulators just think this is ATM a little bigger.

We do what we can with what we have.  Build each message the best way and make sure they all work better inside the Auth wrapper.

And this does not obviate the need for privacy of the operator information.  That would still need to be encrypted.

All a work in progress.  Too many SDOs and regulators involved.
On 4/1/20 2:49 AM, Björn Haase wrote:
I fear that you might actually need at least some more bytes of payload in order to get any sound scheme realized.
For preventing replay attacks a 32 bit nonce and a 32 bit authentication tag might have to be considered to form the bare minimum requirement ☹.

We have had a similar problem with the severely size-limited BluetoothLE advertising (broadcast) packets.
One option that we use is segmenting the information by splitting it into several packets. This way reception of two or more separate
packets is needed in order to get the full information.

Mit freundlichen Grüßen I Best Regards

Dr. Björn Haase

________________________________
Senior Expert Electronics | TGREH Electronics Hardware

Endress+Hauser Liquid Analysis

Endress+Hauser Conducta GmbH+Co.KG | Dieselstrasse 24 | 70839 Gerlingen | Germany
Phone: +49 7156 209 377 | Fax: +49 7156 209 221
[email-masked]<mailto:[email-masked]> | www.conducta.endress.com<http://www.conducta.endress.com/>
________________________________

Endress+Hauser Conducta GmbH+Co.KG
Amtsgericht Stuttgart HRA 201908
Sitz der Gesellschaft: Gerlingen
Persönlich haftende Gesellschafterin:
Endress+Hauser Conducta
Verwaltungsgesellschaft mbH
Sitz der Gesellschaft: Gerlingen
Amtsgericht Stuttgart HRA 201929
Geschäftsführer: Dr. Manfred Jagiella

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