Re: [Lwip] [SPAM?] Re: Notes on draft-tschofenig-lwig-tls-minimal-03

[Behcet Sarikaya <[e-mail]>]

I think that Tiny DTLS with raw public key support is good to have.

My question is: is the implementation following
draft-ietf-tls-oob-pubkey?

Regards,

Behcet


On Tue, Aug 27, 2013 at 5:52 PM, Hauke Mehrtens <[e-mail]> wrote:

> Hi Sye Loong,
>
> I am using a simulated sensor node in cooja. wismote is a simulated
> wireless sensor node which simulates a TI MSP430 with 16kB RAM and 128
> kB Rom, so this suites in the class 1 category.
> Currently I am still in the state of getting tinydtls working on the TI
> MSP430.
>
> Hauke
>
> On 08/27/2013 03:32 AM, Keoh, Sye Loong wrote:
> > Hi Hauke,
> >
> > What is a wismote? Do you have a use case for your work? and what are
> > the assumptions of the nodes in your network? Are they class 1 devices
> > as defined in the Terminology draft?
> >
> > Great that you are willing to contribute!
> >
> > cheers
> > Sye Loong
> >
> > -----Original Message----- From: Hauke Mehrtens
> > Sent: Monday, August 26, 2013 10:42 PM
> > To: Sye Loong Keoh
> > Cc: [e-mail] ; [e-mail] ;
> [e-mail]
> > Subject: [SPAM?] Re: [Lwip] Notes on draft-tschofenig-lwig-tls-minimal-03
> >
> > Hi Sye Loong,
> >
> > I am currently at implementing reordering, it seams to work, but it is
> > not committed to github yet.
> >
> > I am also sending only one message at a time, so a flight contains many
> > UDP packages.
> >
> > I am currently trying to get it to work in cooja on a simulated wismote,
> > the psk handshake already works, but I still have problems with the
> > ECDH_ECDSA handshake, something is probably wrong in the ecc code, on
> > x86 it works. Cooja also has a nice tool which shows the stack usage of
> > the application running.
> >
> > Too bad you can not give me access to your modified tinydtls version.
> >
> > Most of my code is at github, it misses some of the things that I am
> > currently working on and that are not cleaned up right now.
> >
> > I want to do some measurements similar to the ones, you did for the psk
> > case with ECDH_ECDSA for my master's thesis and I would like to get them
> > integrated into the draft.
> >
> > Hauke
> >
> > On 08/26/2013 12:04 PM, Keoh, Sye Loong wrote:
> >> Hi Hauke,
> >>
> >> Thank you for your interest in our draft. It is great to hear that you
> >> are extending TinyDTLS with raw public key support, and this is indeed
> >> the contribution that we needed in this document, as we only had
> >> performance and implementation details of PSK in TinyDTLS.
> >>
> >> At least in your implementation, we needed the re-ordering because
> >> messages were not sent using message flights. Each message is sent
> >> individually.
> >>
> >> I am sorry that the the modified TinyDTLS code cannot be made available
> >> due to some constraints that we have. But, we can discuss specific needs
> >> that you have.
> >> When you compile and flash the application to the hardware, you can get
> >> the RAM size measurement.
> >>
> >> Would be great if you could share your implementation details and
> >> measurements with us, so that they can be incorporated into our Internet
> >> Draft.
> >>
> >> cheers
> >> Sye Loong
> >>
> >>>>>
> >> Hi Hannes,
> >>
> >> I have some notes on
> >> https://tools.ietf.org/html/draft-tschofenig-lwig-tls-minimal-03
> >>
> >> I am working on tinyDTLS and came across some problems. I extended it to
> >> support raw public keys with TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 on the
> >> SECP256R1 curve. The ECC code just supports this specific curve.
> >>
> >> The ClientHello without a cookie is now 99 Bytes big (value in UDP
> >> header) and on ieee802.15.4 it has to be fragmented somewhere. But to do
> >> fragmentation we have to store a state somewhere.
> >>
> >> For retransmission, instead of storing the whole message you could store
> >> the data which is needed to recreate the message. Data like the server
> >> certificate already has to be stored somewhere. I am planing to
> >> implement this.
> >>
> >> We have a high memory consumption in the handshake process, you could
> >> make it possible to be able to just do one handshake at a time, but have
> >> more than one DTLS session open at a time. All these DTLS session will
> >> then share a common memory space to store their temporary handshake
> >> data. I am planing to implement this.
> >>
> >> If you have a pretty reliable medium you could leave out implementation
> >> of reordering, the other peer will resend the messages if a message will
> >> be lost and then the client could start at the position where the
> >> package was lost again. This could save some ram to store the messages.
> >>
> >> Is the code of the modified tinyDTLS version and a more detailed
> >> description of the setup available somewhere? I am planing to so some
> >> measurements with tinyDTLS and raw public keys. How was the RAM size
> >> measurement done?
> >>
> >> As already discussed in the meeting the sizes for the tls implementation
> >> are pretty big. I haven't implemented a generic ASN.1 parser, I am just
> >> supporting one type of raw public key, so I am doing a memcmp() to
> >> ensure it is the one I excepted, then there is the public key at a
> >> constant offset.
> >>
> >> My tinyDTLS implementation with raw public keys and
> >> TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 on the SECP256R1 curve is about 30%
> >> bigger then the version just supporting PSK cipher. This measurement was
> >> done on a AMD64 system without any compiler optimization for size. I am
> >> planing to do a better measurement.
> >>
> >> Hauke
> >>
> >> [0]: https://github.com/hauke/tinydtls/tree/ecdh-merge
> >
>
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