Re: [Lwip] WGLC for draft-ietf-lwig-crypto-sensors-02

[Zhen Cao <[e-mail]>]

Hi Hannes,

Thanks for the frank points, which are helpful to make documents more
impactful.  Please see my discussion in-line.

On Mon, Mar 6, 2017 at 9:36 PM, Hannes Tschofenig <[e-mail]
> wrote:

> Hi all,
>
> as I mentioned in the past I consider this document problematic.
>
> The selected hardware gives the impression that IoT devices need very
> low requirements. This gives inexperienced readers the wrong impression.
>

I do not think this leads to any incorrect impressions.  It clearly states
the platform that this work has been carried out, and by informed selection
of crypto libraries, security functions can be enabled on such IoT
devices.  It's much better than the other opposite impression that security
is costly and could be avoid as far as we can.


> At no point in the document it explains why a typical software stack
> required for an IoT device would fit on hardware that has 2 kB of SRAM,
> and 32 kB of flash memory. What did you put on that device? (CoAP, DTLS,
> Resource Directory, SENML -- protocol talk about in Section 9) I suspect
> that there is no firmware update mechanism in place, which is a
> typically demanded feature for IoT devices in order to address bugs.
>
> Other IETF publications recommend key sizes of at least 112 bits
> (symmetric). Here is the relevant table from RFC 4492:
>

Is this 112 bits of symmetric encryption mandatory for even tiny devices?
If this is only a recommended value, we can encourage the contributors to
generate some reference benchmarks for longer asymmetric key values.


>
>                        Symmetric  |   ECC   |  DH/DSA/RSA
>                       ------------+---------+-------------
>                            80     |   163   |     1024
>                           112     |   233   |     2048
>                           128     |   283   |     3072
>                           192     |   409   |     7680
>                           256     |   571   |    15360
>
> The document, however, describes RSA key sizes of 64, 128, 512 and 2014
> bits! It makes no sense to illustrate performance, and memory
> requirements of key sizes that shouldn't be used in today's IoT hardware.
>
> The document says that it describes smart object implementation
> experience but clearly this is far away from real world product
> experience. The need for a random number generator is essentially
> missing and a reference to a software library does not help either.
>
> I believe you have started with some hardware and then created the
> software & performance measurements. The recommended approach is,
> however, to first think about security and the requirements and
> subsequently think about what hardware supports the security
> requirements and therefore mitigates the threats.
>

The recommended approach is definitely right for any product design.  But
considering the various requirements with different security needs, it is
pretty hard to cover all of them in one draft.   How about to also include
some discussion of the limitations of doing this in other scenarios that
may break security.


>
> The document references several work in progress specifications. Also
> the pointers to specifications like HIP or IPsec for use with IoT
> devices is misleading since they are not reflecting industry practice.
> They are at best university research projects.


Thanks for checking this.  I think Mohit can try to figure out and change
these inappropriate citations .

Will wait for @Mohit's response anyway.

Best regards,
Zhen


> Ciao
> Hannes
>
>
> On 03/06/2017 10:35 AM, Mudugodu Seetarama Raghavendra wrote:
> > +1
> >
> >
> > Regards,
> >
> > Raghavendra
> >
> >
> >
> > ------------------------------------------------------------------------
> > *From:* Lwip <[e-mail]> on behalf of Rahul Jadhav
> > <[e-mail]>
> > *Sent:* Saturday, March 4, 2017 7:30 PM
> > *To:* [e-mail]
> > *Subject:* Re: [Lwip] WGLC for draft-ietf-lwig-crypto-sensors-02
> >
> > The draft provides useful information to implementors about different
> > challenges related to security aspects especially towards using low-end
> > hardware. The deployment model described with the experiences will prove
> > helpful to implementors. Will be helpful to take this work forward.
> >
> > Regards,
> > Rahul
> >
> > On 22 February 2017 at 08:45, Zhen Cao <[e-mail]
> > <mailto:[e-mail]>> wrote:
> >
> >     Hello everyone,
> >
> >     This email starts the WGLC for draft-ietf-lwig-crypto-sensors-02
> >     (https://tools.ietf.org/html/draft-ietf-lwig-crypto-sensors-02
> >     <https://tools.ietf.org/html/draft-ietf-lwig-crypto-sensors-02>)
> >
> >     Could you help review the document and send your comments to the
> >     mailing list. Thank you in advance.
> >
> >     The WGLC will end in two weeks from now.
> >
> >     BR,
> >     Zhen
> >
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> >
> >
> >
> >
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